Design of the GIS

Prepared under the:

Local Government GIS Demonstration Grant

Supported by:

Local Government Records Management Improvement FundLocal Government Records ServicesState Archives and Records Administration

Project Team:

Erie County Water AuthorityMr. Paul Becker, Project Manager

National Center for Geographic Information and AnalysisState University of New York at BuffaloDr. Hugh Calkins, Project DirectorMs. Carmelle J. CôtéMs. Christina Finneran

GIS Resource Group, Inc.Mr. Graham Hayes, PresidentMr. Thomas Murdoch, Vice-President

For More Information, Contact:

Local Government Technology ServicesState Archives And Records Administration9B38 Cultural Education CenterAlbany, New York 12230Phone: (518) 474-4372Fax: (518) 473-4941

GIS DEVELOPMENT GUIDE

Volume 1

Table of Contents

MANAGER'S OVERVIEW

Introduction ......................................................................................... 1Geographic Information Systems: Definitions and Features......................... 3Enterprise-wide GIS: The Corporate Database........................................... 5Policy Issues in GIS Development ............................................................. 6Management Issues in GIS Development .................................................... 7Geographic Information Systems: The Development Cycle ......................... 9Tasks for GIS Development and Use.........................................................10Summary ........................................................................................16References ........................................................................................17Glossary ........................................................................................19

Figures1 - GIS Development Process.........................................................112 - Life-Cycle of a GIS Database ....................................................13

NEEDS ASSESSMENT

Introduction...........................................................................................27Conducting a Needs Assessment ..............................................................28Local Government Uses of GIS................................................................29Data Used by Local Government..............................................................32Documenting GIS Needs..........................................................................33Documenting an Activity-Type Use of the GIS ..........................................36Master Data List.....................................................................................37Conducting Interviews ............................................................................38Preparing the Needs Assessment Report....................................................40Summary...............................................................................................44

AppendicesA - GIS Application Description Forms .........................................A-1B - Full-Page Sample of Master Data List ......................................B-1C - Sample GIS Application Description ........................................C-1D - Data Flow Diagraming Symbols ..............................................D-1E - Sample Application Descriptions and Summary Tables...............E-1

Needs Assessment cont'd

Figures1 - GIS Application Descriptions ....................................................332 - Data Flow Diagram Example ....................................................363 - Master Data List ......................................................................374 - Interviewing and Documenting Needs ........................................395 - List of GIS Applications ...........................................................406 - Table Summarizing Applications Example..................................417 - GIS Applications/Data Matrix....................................................418 - GIS Functions List ...................................................................429 - Compiling Results of Needs Assessment Example........................43

CONCEPTUAL DESIGN OF THE GIS

Part 1 Data Modeling

Introduction ........................................................................................46Nature of Geographic Data......................................................................48Entity Relationship (E-R) Data Modeling..................................................49Geographic Data Models .........................................................................53Methodology for Modeling......................................................................55Developing a Spatial Data Model (Entity-Relationship Diagram) .................58Summary of Conceptual Data Modeling....................................................59

Part 2: Spatial Data Standards and Metadata Requirements

Metadata Tables......................................................................................61Additional Reading.................................................................................64Appendix A ......................................................................................A-1

Figures 1 - GIS Development Process.........................................................45 2 - Life-Cycle of a GIS Database ....................................................46 3 - Entities ...................................................................................49 4 - Example of a Firm's Database...................................................50 5 - Example of Simple E-R Diagrams .............................................50 6 - Simple E-R Diagrams...............................................................52 7 - Spatial Relationships.................................................................54 8 - Entity Symbol for Spatial Objects..............................................56 9 - Entity Relationship Symbols......................................................57

10 - Diagramming a Spatial Relationship...........................................5811 - Example of Entity Relationship Diagram for Local Government...59

GIS DEVELOPMENT GUIDE: MANAGER'S OVERVIEW

11 INTRODUCTION

This guide is the first of a set of technical support documents to assist local governmentsindeveloping a GIS. The set of guides describes procedures and methods for planning theGIS,evaluating potential data sources, testing available hardware and software and planning foritsacquisition, building the GIS data base, developing GIS applications, and planning for the longtermmaintenance of the GIS system and data base. These guides are intended to provide adviceon howbest to accomplish the GIS development tasks for all levels of local government - fromlarge,urbanized counties to small rural towns to special-purpose districts.

Realistically, large comprehensive GISs will be developed by the larger units of government(counties and cities) individually or, most likely as the leader in a cooperative multi-participanteffort. These would involve the individual operating units within that government and/or thesmaller units of local government within the common land area of the larger leading unit.Typically, we would expect to see county government taking the lead, but also covering the interestof all other governmental units within the county. Occasionally, there will be situations wheresmaller units of government (town, special purpose district, or limited purpose GIS application)may have to "go-it-alone" in developing the GIS. These guidelines have been written to mainlyaddress the first case - a county leading a consortium or cooperative effort. Thus, we wouldexpect the GIS development team of a county to be the primary user of these guidelines, in thesense of actually performing the tasks outlined in each document. However, this does notmean the other participants in a GIS should stop reading these guidelines at thispoint. It is critically important for all expected participants in a cooperative GISventure to fully understand the development process. If a smaller unit ofgovernment is to reap the benefits of a county-level GIS, they must activelyparticipate in the planning and development effort.

The procedures are applicablefor use in first-time creation of a GIS, for restructuring an on-goingGIS development project, andfor the review and further development of an existing GIS. Thesubject matter of the guidesidentifies the necessary tasks in a GIS development program,describes appropriate methods toaccomplish each task and, where applicable, provides examplesand illustrations of documents orother products that result from each task.

The guidelines are designed for use by general-purpose local governments (city, county, town, orvillage), special purpose governments (utilities, school districts, etc.), and by those who provideassistanceto local governments (consultants, academic units, etc.). The guides address thetechnical stepsrequired to create a GIS, the management tasks required to ensuresuccessfuldevelopment of the GIS, and the policy issues that should be considered for theeffective use of theGIS.

The Role Of Management

Although GIS is often viewed as an arena for the technically sophisticated computerprofessional,the development of a successful government-based multi-participant GIS is very dependent on

2 GIS Development Guide

propermanagement participation and supervision. Normal, common-sense management practicesare asnecessary in a GIS project as in any other major undertaking. In fact, our experience hasshown thatthe recommended management actions may be the most critical aspect of the GISdevelopmentprocess. GIS development is a process of technological innovation andrequires managementattention appropriate to this type of activity - active as opposedto passive management involvement in theproject. Historically, much of the disillusions anddisappointment with GIS projects stems not froma failure of the technical components of the GISbut rather from a lack of understanding of theprocess of technology innovation and the lack ofrealistic expectations of all parties associated withthe project (GIS technicians, potential users,managers, and elected/appointed officials).

Applying The GIS Development Guides By Local Governments In New YorkState

The overall procedure contained in the GIS Development Guides is very comprehensive andcanrequire considerable time, effort and dollars to complete. This raises the questions:

• Does all ofthis have to be done?• What level of detail is appropriate?• How can smaller governments,villages and towns, special purpose districts,

or a single department in a larger jurisdiction, get through this process?

Does everything have to be done? . . level of detail?

Basically, yes. However, the steps in the GIS development process are frequently done inan iterative manner over an extended time period. Also, the steps are not completelyindependent of one another and so some back-and-forth does happen. It is often useful tomake a "first-cut" run through the entire process, writing down what is already known andidentifying the major questions that need to be answered. The person who will bemanaging the development process may be able to do this "first-cut" description in 1 to 2days. This can be very helpful in getting a feel for the scope of the whole process andthen can be used as a decision tool for continuing. The number of times the process isconducted, the amount of detail, and the resources needed to complete the study can bebalanced in this way. If the intended implementation will be limited or small, theplanning effort and documents can be sized accordingly. It is important, however, thateach step be considered and completed at some level. The companion GIS Designsoftware package that accompanies these guides provides a structure and makes it easy torecord the information developed during the planning process - application descriptions,data model, data dictionary, metadata, logical database design, and record retentioninformation.

How can smaller units of local government, such as villages and small towns complete aGIS Plan?

The best situation for a village, small town, or even a smaller, rural county is to be apartner with a larger unit of government, a county, regional agency or utility company thatis conducting and/or leading a GIS planning exercise. Participating in a regional GIScooperative, or joining an existing one, will provide access to GIS technical expertise andspatial data created by other agencies. Additionally, if one is a partner in a larger group,

Manager's Overview 3

the activities directed toward the evaluation and selection of the GIS hardware andsoftware may not need to be completed. One would simply use the same GIS system inuse by the larger agency or group. Only the activities aimed at defining applications (uses)and identifying the needed data would need to be done by the smaller unit of government.In such a situation, the larger unit of government assumes the leadership role for the area-wide GIS and should have the technical expertise to assist the smaller unit. In situationswhere a larger effort does not exist, a village or town government may want to look at aGIS installation in a similar village or town elsewhere in the state. Given the similarities inlocal governments within the state, the adoption of the GIS plan of another unit is notunreasonable. That plan should be carefully reviewed by the intended participants in theGIS to ensure applicability. After modifying and validating the plan, a schedule for GIShardware, software and data acquisition can be prepared consistent with availableresources. If a good plan is prepared, there is no reason data acquisition (the mostexpensive part of a GIS) cannot be stretched over a long time period. Significant dataalready is available from state and federal agencies at reasonable costs. These data canform the initial GIS database, with locally generated data added later. A list of state andfederal data sources is contained in the Survey of Available Data Guide.

Content Of This Guide

This guide presents an overview of the GIS development process. This process is presented asasequence of steps conducted in a specific order. Each step is important in itself, butmoreimportantly, information needed to complete subsequent steps is assembled and organized ineachprevious step. The underlying philosophy of the entire series of documents isto concentrate on the GIS data. As well as being the most expensive part of any GIS, thedata must be collected, stored, maintained, and archived under an integrated set of activities inorder to ensure continued availability and utility to the initial users as well as future users,including the general public. Defining and documenting data elements from their initial definitionin the needs assessment through to proper archiving of the GIS database according to staterequirements is the constant theme of these guidelines.

22 GEOGRAPHIC INFORMATION SYSTEMS: DEFINITIONS AND FEATURES

Basic Definition Of A Geographic Information System (GIS)

A geographic information system (GIS) may be defined as "...a computer-basedinformationsystem which attempts to capture, store, manipulate, analyze and display spatiallyreferenced andassociated tabular attribute data, for solving complex research, planning andmanagement problems"(Fischer and Nijkamp, 1992). GISs have taken advantage of rapiddevelopments inmicroprocessor technology over the past several decades to address the specialchallenges of storingand analyzing spatial data. Geographers have referred to GISs assimultaneously providing "...thetelescope, the microscope, the computer and the Xerox machine"for geographic and regionalanalysis (Abler, 1987).


Unique Features Of A GIS - Why Planning Process Is Needed

GIS belongs to the class of computer systems that require the building of large databasesbeforethey become useful. Unlike many micro-computer applications where a user can begin useafterthe purchase of the hardware and software, the use of a GIS requires that large spatialdatabasesbe created, appropriate hardware and software be purchased,applications be developed, and allcomponents be installed, integrated and testedbefore users can begin to use the GIS. These tasks are large and complex, so large infact,as to require substantial planning before any data, hardware or software is acquired. Thefocus ofthe GIS Development Guides is to describe the GIS planning process and to provideexamples ofhow to accomplish the recommended planning tasks.

History Of Technology Innovations - GIS Is A Technology Innovation

It is useful to note that GIS is, at present, a technological innovation. The adoption oftechnologicalinnovations (i.e., the development of a GIS for a local government) is not always astraightforwardprocess, such as one might expect with the installation of something that is notnew. Severalproblems are likely to occur such as:

• Staff not fully understanding the technology prior toextensive training• Development time estimates differing from actual task times• Greateruncertainty about costs• A greater likelihood that programmatic changes will be needed duringthe development

phases, etc.

The significant management point here is that these are normalconditions in theadoption of a new technology. Management needs to anticipate that sucheventswill happen, and when they do, take appropriate management actions.

The adoption of computer technology by an organization either GIS or other applications,introduces fundamental change into the organization in its thinking about data. Priorinformationtechnology allowed data to be collected and related to activities and projectsindividually. Organized stores of data were the exception rather than common practice. This ledto duplicate datacollection and storage (as in different departments) and to the possibility oferroneous data existing in one ormore locations. One of the goals of computer systems anddatabase development is to eliminateredundant data collection and storage. The principle is thatdata should be collected only once andthen accessed by all who need it. This not only reducesredundancy; it also allows for more accuratedata and a greater understanding of how the samedata is used by multiple departments. The necessary condition for successful computer system anddatabase development is fordifferent departments and agencies to cooperate in the development ofthe system. A databasebecomes an organization-wide resource and is created and managedaccording to a set of databaseprinciples.


3 3 ENTERPRISE-WIDE GIS: THE CORPORATE DATABASE

The role of a GIS in a local government setting is more than simply automating a few obvioustasksfor the sake of efficiency. A local government (or several cooperating governments) shouldviewthe GIS project as an opportunity to introduce fundamental change into theway its business isconducted. As with the adoption of management and executiveinformation systems in the businessworld, the adoption of GIS effectively reorganizes the dataand information the government collects,maintains and uses to conduct it affairs. This can, andarguably should, lead to major changes inthe institution, to improve both effectiveness andefficiency of operations.

A key factor in the success of computer system adoption in the business world is the concept ofthe"enterprise" or "corporate" database. As implied by the name, the corporate database is asingle,organization-wide data resource. The advantages of the corporate database arefirst, that all usershave immediate and easy access to up-to-date information and, secondly that theconstruction of thedatabase is done in the most efficient manner possible. Typically, thecorporate database eliminatesredundant collection and storage of information and the keeping ofextra copies of data and extrareference lists by individual users. Here, we are recommending theuse of corporate database concept to integrate GIS data for all units of local governmentparticipating in a cooperative GIS program.

An effective corporate database does require cooperation on the part of all users, both forthecollection and entry of data in the database and in developing applications in a shared datacontext. This may result in some individual applications or uses being less efficient, however theoverallbenefits to the organization can easily outweigh these inefficiencies. Greater emphasismust,however, be placed on maintaining a high quality of data and services to users, mainly tooffset theperceived loss of control that accompanies sharing an individual's data to another part oftheorganization.

The corporate database concept can be used in the governmental situation, for either single unitsofgovernment or between several governmental entities in the same region. The benefitsassociatedwith the corporate database can be achieved if governmental units are willing tocooperate andshare a multi-purpose regional GIS database. Such an arrangement has sometechnicalrequirements; however, establishing the corporate database is much more aquestion of policy , management cooperation and coordination.

44 POLICY ISSUES IN GIS DEVELOPMENT


There are several policy issues that need to be addressed early in the GIS planning process:

GIS Project Management

Adequate management attention has already been mentioned in this document. As GIS is stillanevolving new technology, the individuals involved (management, users, GIS staff) may haveverydifferent expectations for the project, some based on general perceptions of computing,which mayor may not be correct. This, along with the long time period for developing the GIS,makes it veryimportant for substantial involvement of management in the project. Several factorsassociated withsuccessful GIS projects are:

• Emphasize advantages of GIS to individual users and entire organization• Require high level of competency by all participants• Ensure high level of management commitment from all management levels in the

organization• Require participation in team building and team participation within & between

departments• Ensure minimum data quality and access for all users• Require development team to set realistic expectations• Minimize time between user needs assessment and availability of useful products.• Develop positive attitude toward change within organization• Ensure level of technology is appropriate for intended uses• Highly visible Pilot Project that is successful

Data Sharing

The sharing of data among government agencies is a virtual necessity for asuccessful, long-term GIS. Not even the most affluent jurisdictionswill be able to justify "going-their-own-way" and not taking advantage of what data areavailable from other sources or notsharing their database with other governmental units. This, then, raises several questions that mustbeconsidered during the planning of the GIS:

• What will be the source for each data item?• How will sharing be arranged? . . purchase? . . license? . . other agreement?• Who will own the data?• How will new GIS data be integrated with existing data files (legacy systems)?• Who will be responsible for updates to the data?• How will the cost of the data (creation and maintenance) be allocated?• Who will provide public access to the data?• Who will be responsible for data archiving and retention? . . of the original? ..of

copies?

These questions do not, at this time, have good answers. Currently, the Freedom ofInformationregulations require that all government data be made available to thepublic at minimal cost (cost ofmaking a copy of the data). No distinction is made onthe basis of the format of the data (eye-readable or digital), the amount of data, or theintended use of data. Thus, the question of sharingthe cost of a GIS database cannotbe addressed in general. If data can be obtained free from


another agency, why enter into anagreement to pay for it? The answer is, of course, that thecreating agency will not beable to sustain the GIS database under these circumstances. However,at this time , the set of state laws and regulations applicable to GIS data are notadequate to resolvecost issues and to facilitate regional data sharingcooperatives. New legislation willbe required. The New York State Temporary GIS Councildid submitrecommendations on these issues to the Legislature in March 1996. Additionally,theNew York State Archives and Records Administration is currently in the process ofpreparingrecord management and retention schedules suitable for GIS data, both inindividual agencies andfor shared databases. The New York State Office of Real Property Services has been designatedas the GIS representative on the Governor's Task Force for Information Resource Management.One of the charges that has been given to the Task Force is to design a cohesive policy for thecoordination of geographic information systems within New York building on the work of theTemporary GIS Council. Further information should be availablein late-1996 that should clarifythe issues associated with arranging for data sharingamong governments.

55 MANAGEMENT ISSUES IN GIS DEVELOPMENT

Expected Benefits From The GIS

Local government need for, and use of, a GIS falls into several categories: maintainingpublicrecords, responding to public inquiries for information, conductingstudies and makingrecommendations to elected officials (decision-makers), andmanaging public facilities and services(utilities, garbage removal,transportation, etc.). The GIS tasks that meet these uses are:

• Providing regular maps• Conducting spatial queries and displaying the results• Conductingcomplex spatial analyses

Many of these tasks are already done by local government, althoughby manual means. The GISis able to perform these tasks much more efficiently. Some of theanalytical tasks cannot beperformed without a computer due to their size and complexity. In thesecases, the GIS improveslocal government effectiveness by providing better information to plannersand decision-makers.

Benefits from using a GIS fall into the two categories of: efficiency and effectiveness.Existingmanual tasks done more efficiently by the GIS result in a substantial savings of stafftime. In thelocal government context, the largest savings come from answering citizen inquiriesof many types. Depending on the size of the government, savings using the query function ofa GIS can rangefrom 2 person-years for a smaller town, to 5-8 person years for a large town, to10 or more person-years for a large county. Estimates of potential time savings can be derived bymeasuring the timeto respond to a query manually and by GIS and multiplying the difference bythe number ofexpected queries. This information is usually gathered during the NeedsAssessment. Effectivenessbenefits are more difficult to estimate. The GIS may be used toaccomplish several tasks that werenot previously done due to their size and complexity (e.g.,flow analysis in water and sewer systems,traffic analysis, etc.). As these are essentially newtasks, a comparison between manual and GISmethods is not possible. While not measurable, thebenefits from these applications can besubstantial. Generally categorized as better planning,better or more effective decision-making,these applications support more effective


investment of government resources in physicalinfrastructure where relatively small performanceimprovements can translate into large dollarsavings. GIS also provides an effective way tocommunicate the problem and solution to the general public and other interested parties

Resources Required To Develop A GIS

Developing a GIS involves investment in five areas: computer hardware,computer software,geographic data, procedures and trained staff. The acquisitionof the computer hardware andsoftware are often incorrectly viewed as the most expensive activityin a GIS program. Research, someconducted at the National Center for Geographic Informationand Analysis at SUNY-Buffalo, hasdemonstrated that developing the geographic database(which includes some of the procedure andstaff costs) can account for 60% to80% of the GIS development costs. Continuing costs foroperation and maintenance arealso dominated by the data costs. Coordination of GIS programs,particularly among several localgovernment agencies, can minimize the cost of databaseconstruction and maintenance, and canprovide for the greatest use of the database, which givesmaximum benefits from the investment.

Staffing Requirements For A GIS

Staffing for a GIS is a critical issue. In general, it is not easily feasible to directly expand thelocalgovernment staff positions to fill the GIS need. There are three areas where expertise isneeded:

• Management of the GIS project (GIS project manager)• GIS database skills (usually called a database administrator)• Application development for database and users (a GIS software analyst)

Initial creation of the GIS database (digitizing) will require an appropriatelysized clerical staff,dependent on the amount of data to be converted. Alternatives to staff expansionareconsultants and data conversion firms. GIS database conversion is a front-end staff needthatcan easily be contracted-out (good quality specifications need to be written for this task). If atallpossible, the three functions of GIS manager, GIS software analyst and GISdatabaseadministrator should be fulfilled by staff personnel, either by hiring or by retrainingexistingprofessionals. When necessary, during the start-up phases of GIS development, the GISanalyst anddatabase administrator functions can be done under consultancy arrangements,PROVIDED THATA FULL-TIME GIS MANAGER IS AVAILABLE ON STAFF.

The second need is for training of users in general computing, database principles, and GIS use.These topics are covered in training courses offered by most GIS vendors, and after theGISsoftware has been selected, they are the best source for user training.

Management Decision Points in the GIS Development Program


The "decision" to develop a GIS is made incrementally. The information needed to determinethefeasibility and desirability of developing a GIS is not available until several of the planningstepshave been completed. The key decision points are:

• Decision to investigate GIS for the organization - the initial decision to begin theprocess. This is an initial feasibility decision and is based on the likelihood that a GISwill be useful and effective. It is fairly important to identify the major participants atthis point - both departments within agencies and the group of agencies, particularlykey agencies, the agencies who represent a majority of the uses and who willcontribute most of the data.

• Decision to proceed with detailed planning and design of the database - at this time,theapplications, data required, and sources of the data have been identified.Applications can be prioritized and scheduled and the benefits stream determined.Also, applications to be tested during the pilot study and the specific questions to beanswered by the pilot study will have been determined. A preliminary decision willneed to be made as to which GIS software will be used to conduct the pilot study.

• Decision to acquire the GIS hardware and software - this decision follows thepreparation of the detailed database plan, the pilot study and, if conducted, thebenchmark test. This is the first point in the development process where the costs ofthe GIS can reasonably be estimated, the schedule for data conversion developed, andtargets for users to begin use determined.

66 GEOGRAPHIC INFORMATION SYSTEMS: THE DEVELOPMENT CYCLE

Developing a GIS is more than simply buying the appropriate GIS hardware and software.Thesingle most demanding part of the GIS development process is building thedatabase. This tasktakes the longest time, costs the most money, and requires the most effort interms of planning andmanagement. Therefore the GIS development cycle presented hereemphasizes database planning. Most local governments will acquire the GIS hardware andsoftware from a GIS vendor. Choosingthe right GIS for a particular local government involvesmatching the GIS needs to thefunctionality of the commercial GIS. For many agencies,especially smaller local governments, choosing a GIS will require help from larger, moreexperienced agencies, knowledgeable university persons and from qualified consultants. Bycompleting selected tasks outlined in these guidelines local governments can prepare themselves toeffectively interact and use expertise from these other groups.

The GIS development cycle starts with the needs assessment where the GIS functionsandthe geographic data needed are identified. This information is obtained throughinterviewingpotential GIS users. Subsequently, surveys of available hardware, software and dataare conductedand, based in the information obtained, detailed GIS development plans areformulated.

It is important to involve potential users in all stages of GIS development. They benefit fromthisinvolvement in several ways:


• Describing their needs to the GIS analysts• Learning what the GISwill be capable of accomplishing for them• Understanding the nature of the GIS developmentcycle - the time involved and the

costs.

Potential users need to understand that there may besignificant time lags betweenthe first steps of Needs Assessment and the time when the GIS canactually beused. Mostly, this is due to the size of the database building task, which can take up toseveralyears in a large jurisdiction.

In addition to understanding that database development takes substantial time, users andmanagersneed to appreciate that GIS is a new technology and its adoption often involves someuncertaintythat can cause time delays, on-going restructuring the development program, and theneed to resolveunforeseen problems. This set of guideline documents describes the GISdevelopment process in away that will minimize problems, time delays, cost overruns, etc.;however, the occurrence of thesesituations cannot be completely avoided. The GIS projectteam and management simply have to beaware that some unforeseen events willhappen. GIS development must be viewed as a process rather than a distinct project.

Estimating and planning for the cost of the GIS is a somewhat difficult task. First, it isnecessaryto recognize that the GIS database will likely be the single most costly item - if a localgovernmentdevelops all of the data itself from maps, etc., this cost can be as much as 70 - 80 %of the totalsystem cost. Thus, acquiring digital data from other GIS systems,government sources or the privatesector can be very cost effective. Participatingin, or organizing a regional data sharing cooperativeor district, can also lead to reduced data costs.When planning for the GIS database, long term datamaintenance and retention costsmust be estimated as well as the initial start-up costs. Cooperation betweenagencieswith similar data needs may provide the most effective way to achieve long-term datamaintenance,retention, and archiving.

77 TASKS FOR GIS DEVELOPMENT AND USE

The GIS development cycle is a set of eleven steps starting with the needs assessment andendingwith on-going use and maintenance of the GIS system. These steps are presented here as alogicalprogression with each step being completed prior to the initiation of the next step. Whilethis viewis logical, it is not the way the world always works. Some of the activities in theprocess mayhappen concurrently, may be approached in a iterative manner, or may need to berestructureddepending on the size and character of the local government conducting the study andthe resourcesavailable to plan for the GIS. The GIS development cycle is based on thephilosophy that one firstdecides what the GIS should do and then as a secondactivity decides on how the GIS will accomplisheach task. Under this philosophy,the needs are described first, available resources are inventoriedsecond (data, hardware, software,staff, financial resources, etc.), preliminary designs are createdand tested as a third major set ofactivities, and lastly the GIS hardware and software are acquiredand the database is built.


NeedsAssessment

ConceptualDesign

AvailableData Survey

H/W & S/WSurvey

Pilot/Benchmark

DatabasePlanningand Design

DatabaseConstruction

Aquisition ofGIS Hardwareand Software

GIS SystemIntegration

ApplicationDevelopment

GIS Use andDatabaseMaintenance

Figure 1 - GIS Development Process

Figure 1 shows the GIS development cycle, which is described in terms of 11 major activities.Prior to initiating these studies, the responsible staff in local governments should attendintroductory GIS seminars and workshops, GIS conferences, and meetings of specific GIS users'groups, to obtain a broad overview of what GIS is and how others are using these systems.

The 11 steps of the GIS development cycle are:

1. Needs Assessment 2. Conceptual Design of the GIS 3. Survey of Available Data 4. Survey of GIS Hardware and Software 5. Detailed Database Planning and Design 6. Database Construction 7. Pilot Study/Benchmark Test 8. Acquisition of GIS Hardware and Software 9. GIS System Integration10. GIS Application Development11. GIS Use and Maintenance

These tasks are one way of dividing up the entire set of activities that must be accomplished tobuilda successful GIS. While there are other ways of expressing and organizing these activities,thisparticular structure has been chosen because it emphasizes data development - data definition,datamodeling, data documentation, data capture and storage, and data maintenance and retention.


Theimportant point to be made here is not the order or structure of the tasks, but rather that, onewayor another, all of these tasks must be completed to have a successful GIS.

In some situations, different methods may be more appropriate than those presented in theseguides,or a different level of detail may fit the particular situation of a unit of local government.Nomatter how simple or complex a given GIS environment is, all of the above tasks shouldbecompleted at an appropriate level of detail. In the specific guides of this set, examples ofdifferentlevels of detail will be provided.

The starting point is the needs assessment. It is assumed that the local government has decidedthata GIS may be justified and it is reasonable to expend the resources to further study theproblem. Afinal assessment of the costs and benefits will not be made until several tasks havebeen completedand the nature and size of the resulting GIS can be estimated. In the processpresented here, thisfinal feasibility assessment is made as part of the detailed database planningand design activity.

Each of the major portions of the development cycle identified and briefly described below isfurtherdescribed in a subsequent guideline document.

Needs Assessment

The GIS needs assessment is designed to produce two critical pieces of information:

• Thelist of GIS functions that will be needed• A master list of geographic data.

These twoinformation sets are extracted from a set of GIS application descriptions, a list ofimportant data,and a description of management processes. Standard forms are used to documentthe results ofuser interviews. The information gained in the needs assessment activity goesdirectly intothe Conceptual GIS Design activity.

Conceptual Design of the GIS System

The conceptual design of the GIS system is primarily an exercise in database design. Itincludesformal modeling (preparation of a data model) of the intended GIS database and the initialstagesof the database planning activity. Database planning is the single most importantactivity inGIS development. It begins with the identification of the needed data and goes onto cover severalother activities collectively termed the data life cycle - identification of data inthe needs assessment,inclusion of the data in the data model, creation of the metadata, collectionand entry of the data into thedatabase, updating and maintenance, and, finally, retention accordingto the appropriate recordretention schedule (Figure 2). A complete data plan facilitates all phasesof data collection,maintenance and retention and as everything is considered in advance, dataissues do not becomemajor problems that must be addressed after the fact with considerabledifficulty and aggravation. Theproduct of the conceptual design activity is a data model whichrigorously defines the GIS databaseand supports the detailed database planning activity.


Data ObjectsIdentified DuringNeeds Assessment

Preparation ofData Model

Create InitialMetadata

Add RecordRetention Schedulesto Metadata

Archives

Continuing GISDatabase Maintenance

GIS Database

Prepare DetailedDatabase Plan

Match Needed Datato Available Dataand Sources

Source Documents:Maps, Images, AirPhotos, etc.

Survey and Evaluationof Available Data

Map and TabularData Conversion

Database QA/QC Editing

Database Backups

Figure 2 - Life Cycle of a GIS Database


The conceptual design of the GIS also includes identification of the basic GIS architecture (typeofhardware and GIS software), estimates of usage (derived from the Needs Assessment), andscopingthe size of the GIS system. All of this is done with reference to the existing dataprocessingenvironments (legacy systems) that must interface with the GIS. This guideline alsoincludes a section on metadata and data standards.

Survey Of Available Data

A survey of available data can commence once needed data have been identified in theNeedsAssessment. This task will inventory and document mapped, tabular and digital datawithin thelocal government as well as data available from other sources, such as federal, state, orother localgovernments and private sector organizations. The entries in this inventory mayinclude other GISsystems within the local area from which some of the needed data may beobtained. If there existsan organized data sharing cooperative or other mechanism forgovernment data sharing, it shouldbe investigated at this time. There also exists the possibilitythat one or more of the commercial GISdatabase developers may be able to supply some of theneeded data and should therefore beinvestigated. The documentation prepared at this point will besufficient to evaluate each potentialdata source for use in the GIS. Information collected at thispoint will also form part of themetadata for the resulting GIS database.

Survey Of Available GIS Hardware And Software

Almost all local government GIS programs will rely on commercially available GIS software.Asa result, a survey of the available GIS systems needs to be conducted. During this activity,the GISfunctionality of each commercial GIS system can be documented for later evaluation.

Detailed Database Design And Planning

The detailed database planning and design task includes the following activities: developingalogical or physical database design based on the data model prepared earlier, evaluating thepotentialdata sources, estimating the quantities of geographic data, estimating the cost of buildingthe GISdatabase and preparing the data conversion plan. Concurrent with the detailed planningfor thedatabase, pilot studies and/or benchmark testing that are desired can be executed.Informationgained from these studies and tests will be needed to estimate the size of theequipment (disk space,main memory etc.) and to determine how much application developmentwill be necessary. Subsequently, plans for staffing, staff training, equipment acquisition andinstallation, and usertraining must be completed. After the preparation of all these plans, theentire cost of the GIS willbe known and the final feasibility assessment can be made.

Pilot Study And Benchmark Tests

Pilot studies and benchmark tests are intended to demonstrate the functionality of the GIS software-simply put, what the commercial GIS from the vendor can do. These tests are useful todemonstrate to potential users andmanagement what the GIS will do for them. Also, performancedata of the GIS system can bedetermined.


GIS Database Construction

Database construction (sometimes referred to as "database conversion") is the process ofbuildingthe digital database from the source data - maps and tabular fi les. Thisprocess would have beenplanned during the previous activity and the main emphasis here ismanagement of the activity andquality assurance/quality control of the converted data. Theconversion process is often "contracted-out" and involves large quantities of source maps anddocuments. Close and effective managementis the critical factor in successful data conversion.

GIS System Integration

Unlike many other computer applications, a GIS is not a "plug and play" type system. Theseveralcomponents of a GIS must be acquired according to well documented specifications. Thedatabasemust be created in a careful and organized manner. Once all the individualcomponents have beenacquired, they must be integrated and tested. Users must be introduced tothe system, trained asnecessary, and provided with adequate assistance to begin use of the GIS.Parts of the GIS which may appear to work fine individually may not work properly whenputtogether. The GIS system staff must resolve all the problems before users can access the GIS.

GIS Application Development

"Application" is a general term covering all things that "go on" in a GIS. First,there are "databaseapplications." These are all the functions needed to create, edit, build, andmaintain the database,and are usually carried out by the GIS systems staff. Some users may haveresponsibility forupdating selected parts of the GIS database, however the entire database shouldbe under the controlof a "database administrator." Other applications are termed "userapplications." ContemporaryGISs provide many simple applications as part of the initialsoftware package (e.g., map display,query, etc.). More complex applications, or onesunique to a particular user, must be developedusing a macro-programming language.Most GISs have a macro-programming language for thispurpose (e.g., Arc Macro Language(AML) in ARC/INFO™. and Avenue in ArcView™). Theapplications needing development bythe GIS systems staff will have been described during theNeeds Assessment on the GISApplication forms.

GIS System Use And Maintenance

After having described the rather large task of creating a GIS, we can now say that useandmaintenance of the GIS and its database will likely require as much attention as was needed toinitiallybuild it. Most GIS databases are very dynamic, changing almost daily, and users willimmediatelythink of additional applications that they would like to have developed. Formalprocedures forall the maintenance and updating activities need to be created and followed by theGIS system staffand by all users to ensure continued successful operation of the GIS.


88 SUMMARY

This document has presented an overview of the GIS development process, with anemphasis ondata and database issues. All of the tasks and issues identified in thisdocument will be describedin detail in the remaining eleven guidelines of this series. Theprocedures are presented as"guides," and not as a "cookbook recipe" which must berigorously followed. Each of the majortasks in the GIS development process and theinformation generated within the task should beaddressed in any specific project. Themethods and forms used in this series can be used, oralternatives can be developed,as appropriate to the situation. The one matter to always keep inmind is that the GISplan is a document to communicate user needs to a GISanalyst. The componentsof the plan must contain:

• Descriptions of applications that are understandable to theuser• A logical translation of user requirements to system specifications• Detailed specification suitable for system development

Following the recommendations in these guidelines cannot, unfortunately, guarantee success.Many of the factors, outside the control of the GIS development team, will affect the ultimatesuccess of the GIS - success being defined as use of the GIS by satisfied users. However, theauthors of these guidelines believe that attempting to develop a GIS without following these, orsimilar procedures, substantially raises the probability of an unsuccessful GIS project - either onethat is not useful or one that substantially exceeds both cost and development time estimates.

Finally, although presented here as an independent activity, GIS development must recognize andinterface with other computer systems in local government, such as E911, police and fire dispatch,facilities management systems, etc. . The GIS must not be viewed as independent of the othersystems, but integrated with them, no matter how difficult, to form a true corporate databasefor local government.


REFERENCES

1) Fischer, Manfred M. and Nijkamp, Peter, "Geographic Information System, Spatial Modeling,and Policy Evaluation," Berlin & New York: Springer-Verlag, 1993, pg 42.

2) Abler, R.F., 1987, "The National Science Foundation National Center for GeographicInformation and Analysis" International Journal of Geographical Information Systems, 1, no. 4,303-326.

SUGGESTED READINGS

1. Antenucci, John C., et.al., Geographic Information Systems: A Guide to theTechnology, New York: Van Nostrand Reinhold, 1991 (ISBN 0-442-00756-6)

2. Aronoff, Stan, Geographic Information Systems: A Management Perspective,Ottawa: WDL Publications, 1989 (ISBN 0-921804-00-8)

3. Burrough, P.A., Principles of Geographical Information Systems for LandResources Assessment, Oxford: Oxford University Press, 19865. (ISBN 0-19-854563-0);ISBN 0-19-854592-4 paperback).

4. Huxhold, William E., An Introduction to Urban Geographic Information Systems,Oxford: Oxford University Press, 1991 (ISBN 0-19-506534-4)

5. Korte, George B., A Practioner's Guide: The GIS Book, Sante Fe: OnWord Press,1992 (ISBM 0-934605-73-4)

6. Laurini, Robert and Derek Thompson, Fundamentals of Spatial Information Systems,London: Academic Press Limited (ISBN: 0-12-438380-7)

7. Montgomery, Glenn E., and Harold C. Schuck, GIS Data Conversion Handbook, FortCollins: GIS World, Inc. (ISBN 0-9625063-4-6)

GIS INFORMATION SOURCES

Scholarly journalsThere are a number of scholarly journals that deal with GIS. These are published on an on-goingbasis.

Cartographica - Contact: Canadian Cartographic AssociationCartography and Geographic Information Systems - Contact: American Cartographic

AssociationInternational Journal of Geographical Information Systems - Contact: Keith Clark at

CUNY Hunter College, New York CityURISA Journal - Contact: Urban and Regional Information Systems Association


Trade magazinesThere are a number of trade magazines that are focused on GIS. They are:

GIS WorldGIS World Inc.155 E. Boardwalk DriveSuite 250, Fort Collins, CO 80525.Phone: 303-223-4848Fax: 303-223-5700Internet: [email protected]

Business GeographicsGIS World, Inc.155 E. Boardwalk Drive, Suite 250Fort Collins, CO 80525.Phone: 303-223-4848Fax: 303-223-5700.Internet: [email protected].

Geo Info SystemsAdvanstar Communications859 Williamette St.Eugene, OR., 97401-6806Phone: 541-343-1200Fax: 541-344-3514Internet:[email protected] site:http://www.advanstar.com/geo/gis

GPS WorldAdvanstar Communications859 Williamette St.Eugene, OR., 97401-6806Phone: 541-343-1200Fax: 541-344-3514Internet:[email protected]

WWWsite:http://www.advanstar.com/geo/gis

Conference Proceedings

American Congress on Surveying and Mapping (ACSM)5410 Grosvenor LaneBethesda, MD, 20814Phone: 301-493-0200Fax: 301-493-8245

American Society for Photogrammetry and Remote Sensing(ASPRS) & (GIS/LIS)5410 Grosvenor LaneBethesda, MD, 20814Phone: 301-493-0290Fax: 301-493-0208

Association of American Geographers (AAG)1710 Sixteenth St. N.W.Washington D.C., 20009-3198Phone: 202-234-1450Fax: 202-234-2744

Automated Mapping/Facility Management International (AM/FM International)14456 East Evans Ave.Aurora, CO, 80014Phone: 303-337-0513Fax: 303-337-1001

Canadian Association of Geographers (CAG)Burnside Hall, McGill UniversityRue Sherbrooke St. WMontreal, Quebec H3A 2K6Phone: 514-398-4946Fax: 514-398-7437

Canadian Institute of Geomatics (CIG)206-1750 rue Courtwood CrescentOttawa, Ontario, K2C 2B5Phone: 613-224-9851Fax: 613-224-9577

Urban And Regional Information Systems Association (URISA)900 Second St. N.E., Suite 304Washington, D.C. 20002Phone: 202-289-1685Fax: 202-842-1850

GlossaryAccuracy - Degree of conformity with a standard, or the degree of correctness attained in a measurement. Accuracy relatesto the quality of a result. If accuracy is relative, the position of a point is defined in relation to another point. It is lessexpensive to build a GIS in the context of relative accuracy. If accuracy is absolute, the position of a point is defined by acoordinate system. Building a GIS in the context of absolute accuracy requires use of the global positioning system.

Accuracy Requirement - statement of how precise the desired results must be to support a particular application.

Adjoin ing Sheets - Maps that are adjacent to one another at the corners and on one or more sides.


Aerial - Relating to the air atmosphere, being applicable in a descriptive sense to anything in space above the ground andwithin the atmosphere.

Aerial Photography - The method of taking photographs from an aerial platform (aircraft). (1.) Vertical photography,some times called orthophotography (see entry) is used for photogrammetric mapping and requires a high degree ofaccuracy. (2.) Oblique photography is used for general information, sometimes to verify certain attributes, but does notprovide accurate measurements for photogrammetric mapping.

Aerial Survey - A survey utilizing aerial photography or from remote sensing technology using other bands of theelectromagnetic spectrum such as infrared, gamma or ultraviolet.

Algori thm - A set of instructions; ordered mathematical steps for solving a problem like the instructions in a computerprogram.

Al ignment - Relates to survey data transposed to maps. The correct position of a line or feature in relation to other linesor features. Also the correct placement of points along a straight line.

Alphanumeric - A combination of alphabetic letters, numbers and or special characters. A mailing address is analphanumeric listing.

Analog Data - Data represented in a continuous form, not readable by a computer.

Area - level of spatial measurement referring to a two-dimensional defined space; for example, a polygon on the earth asprojected onto a horizontal plane.

Attribute - 1. A numeric, text, or image data field in a relational data base table that describes a spatial feature such as apoint, line, node, area or cell. 2. A characteristic of a geographic feature described by numbers or characters, typicallystored in tabular format, and linked to the feature by an identifier. For example, attributes of a well (represented by a point)might include depth, pump type, location, and gallons per minute.AM/FM - Automated mapping/facilities management. A GIS designed primarily for engineering and utility purposes,AM/FM is a system that manages databases related to spatially distributed facilities.

Base Data - set of information that provides a baseline orientation for another layer of primary focus, e.g., roads,streams, and other data typically found on USGS topographic and/or planimetric maps.

Base Line - A surveyed line established with more than usual care upon which surveys are based.

Base Map - A map showing planimetric, topographic, geological, political, and/or cadastral information that mayappear in many different types of maps. The base map information is drawn with other types of changing thematicinformation. Base map information may be as simple as major political boundaries, major hydrographic data, or majorroads. The changing thematic information may be bus routes, population distribution, or caribou migration routes.

Base Station - a GPS receiver on a known location that may broadcast and/or collect correction information for GPSreceivers on unknown locations.

Bench Mark - A relatively permanent point whose elevation above or below an adopted datum is known.

Beta Test - Hardware or software testing performed by users in a normal operating environment; follows alpha testing,which is generally done in the developer's facility.

Bezier - (computer graphics) A curve generated by a mathematical formula in CAD (see entry) programs that maintainscontinuity with other Bezier curves.

Binary - The fundamental principal behind digital computers. Binary means two, computer input is converted into binarynumbers made up of O and 1 (see bit).

BIT: (computers) a binary digit with a value of either 1 or 0.

Block (Tax) - A group of municipal tax lots that can be isolated from other parcels by a boundary, usually a roadway,waterway or properly labeled lot line.

Boundary Line - A line along which two areas meet. In specific cases, the word "boundary" is sometimes omitted, as in"state line", sometimes the word "line" is omitted, as in "international boundary", "county boundary", etc. The term

"boundary line" is usually applied to boundaries between political territories, as "state boundary line", between two states.A boundary line between privately owned parcels of land is termed a property line by preference, or if a line of the UnitedStates public land surveys, is given the particular designation of that survey system, as section line, township line, etc.

BPS - Bits per second, the speed of data transfer.

Buffer A zone of a given distance around a physical entity such as a point, line, or polygon.

CAD/CADD - (Computers) Computer-Aided Design/ Computer-Aided Design and Drafting. Any system for Computer-Aided rather than manual drafting and design. Displays data spatially. on a predefined coordinate grid system, allowing datafrom different sources to be connected and referenced by location. Speeds conventional map development process by 1.permitting replication of shapes, floor plans, etc. from an electric library rather than requiring every component to bedrawn from scratch. 2. Plotters and terminal screens are faster and more accurate than manual drafting. 3. Portions ofdrawings can be edited, enlarged, etc. quickly. 4. Related information can be stored in files and added to drawings in layers.

CAD - (Communication) Computer-Aided Dispatching. Used with emergency vehicles, CAD can be very sophisticated.Online maps of a city can display emergency vehicles as moving dots on the map, their status (enroute to an emergency,awaiting a call, call completed, returning to base, etc.) indicated by different colors. (The acronym for computer-aideddispatch is sometimes confused with computer-aided design.)

Cadastre - a record of interests in land, encompassing both the nature and extent of interests. Generally, this means mapsand other descriptions of land parcels as well as the identification of who owns certain legal rights to the land (such asownership, liens, easements, mortgages, and other legal interests). Cadastral information often includes other descriptiveinformation about land parcels.

Cadastral - Relating to the value, extent and ownership of land for tax purposes. Cadastral maps describe and recordownership. Also called property map.

Cadastral Survey - A survey relating to land boundaries and subdivisions, made to create units suitable for transfer or todefine the limitations to title. Derived from "cadastre", and meaning register of the real property of a political subdivisionwith details of area, ownership, and value. The term cadastral survey is now used to designate the surveys for theidentification and resurveys for the restoration of property lines; the term can also be applied properly to correspondingsurveys outside the public lands, although such surveys are usually termed land surveys through preference. See alsoboundary, survey.

Cartographic (Planimetric) Features - Objects like trees or buildings shown on a map or chart.

Cartography - The technology of mapping or charting features of Earth's topography.

Centroid - The "center of gravity" or mathematically exact center of an irregular shaped polygon; often given as an x, ycoordinate of a parcel of land.

Clearinghouse - a physical repository structure used to accumulate and disseminate digital data and informationconcerning that data. In the GIS context a clearinghouse can contain all or a portion of spatial, metadata and informationaldata.

Cl ient - A software application that works on your behalf to extract some service from a server somewhere on the network.Basic idea, think of your telephone as a client and the telephone company as a server.

COGO - Acronym for Coordinate Geometry achieved via a computer program.

Computer-aided Design or Drafting (CAD) - A group of computer software packages for creating graphicdocuments.

Control Point - A point in a network, identifiable in data or a photograph, with a given horizontal position and aknown surface elevation. It is correlated with data in data set or photograph.

Contour - An imaginary outline of points on the ground which are at the same altitude relative to mean sea level.

Contour Line - A line on a map or chart that connects to points which are at the same elevation.


Contour Map - A map that defines topography (hypsography) by interpreting contour lines as relief.

Control - Also called ground control. A system of survey marks or objects called control points that have establishedpositions and/or elevations verified by ground survey. The marks, or control points, serve as a reference correlating otherdata such as contour lines (see entry) determined from aerial surveys.

Convers ion - 1. The translation of data from one format to another (e.g., TIGER to DXF; a map to digital files).S 2. Dataconversion when transferring data from one system to another (E.g., SUN to IBM).s

Coordinate - The position of point is space in respect to a Cartesian coordinate system (x, y and/or z values). In GIS, acoordinate often represents locations on the earth's surface relative to other locations.

Coordinate System - The system used to measure horizontal and vertical distances on a planimetric map. In a GIS, it isthe system whose units and characteristics are defined by a map projection. A common coordinate system is used tospatially register geographic data for the same area. See map projection

CRT - Cathode Ray Tube. A computer screen or monitor.

CTG - Center for Technology in Government

Data Capture - series of operations required to encode data in a computer-readable digital form (digitizing, scanning, etc.)

Data Dictionary - description of the information contained in a data base, e.g., format, definition, structure, and usage.It typically describes and defines the data elements of the data base and their interrelationships within the larger context ofthe data base.

Data Element - specific item of information appearing in a set of data, e.g. well site locations.

Data Model 1. A generalized, user-defined view of the data related to applications. 2. A formal method for arranging datato mimic the behavior of the real world entities they represent. Fully developed data models describe data types, integrityrules for the data types, and operations on the data types. Some data models are triangulated irregular networks, images, andgeorelational or relational models for tabular data.

Data Quality - refers to the degree of excellence exhibited by the data in relation to the portrayal of the actual phenomena

Data Sets - a collection of values that all pertain to a single subject.

Data Standardization - the process of achieving agreement on data definitions, representation, and structures to whichall data layers and elements in an organization must conform.

Data Structure - organization of data, particularly the reference linkages among data elements.

Database -usually a computerized file or series of files of information, maps, diagrams, listings, location records,abstracts, or references on a particular subject or subjects organized by data sets and governed by a scheme of organization."Hierarchical" and relational" define two popular structural schemes in use in a GIS. For example, a GIS database includesdata about the spatial location and shape of geographic entities as well as their attributes.

Database Management System (DBMS) - 1. The software for managing and manipulating the whole GIS includingthe graphic and tabular data. 2. Often used to describe the software for managing (e.g., input, verify, store, retrieve, query,and manipulate) the tabular information. Many GlSs use a DBMS made by another software vendor, and the GIS interfaceswith that software.

Datum - a mathematical reference framework for geodetic coordinates defined by the latitude and longitude of an initialpoint, the azimuth of a line from this point, and the parameters of theellipsoid upon which the initial point is located.

DEC - Department of Environmental Conservation

Differential Correction - the method (usually done through post processing) of using two GPS receivers, one on aknown location and one on an unknown location, using information from the one on the known location to correct theposition of the unknown location.

Digital Accuracy - refers to the accuracy of digital spatial data capture.

Digital Elevation Model (DEM) - a file with terrain elevations recorded at the intersections of a fine grid andorganized by quadrangle to be the digital equivalent of the elevation data on a topographic base map.

Digital Data - a form of representation in which distinct objects, or digits, are used to stand for something in the realworld--temperature or time--so that counting and other operations can be performed precisely. Data represented digitally canbe manipulated to produce a calculation, a sort, or some other computation. In digital electronic computers, two electricalstates correspond to the Is and Os of binary numbers, which are manipulated by computer programs.

Digital Exchange Format (DXF) 1. ASCII text files defined by Autodesk, Inc. (Sausalito, CA) at first for CAD, nowshowing up in third-party GIS software . 5 2. An intermediate file format for exchanging data from one software package toanother, neither of which has a direct translation for the other but where both can read and convert DXF data files into theirformat. This often saves time and preserves accuracy of the data by not reautomating the original.

Digi ta l Line Graph (DLG) 1. In reference to data, the geographic and tabular data files obtained from the USGS forexchange of cartographic and associated tabular data files. Many non-DLG data may be formatted in DLG format. 2. Inreference to data, the formal standards developed and published by the USGS for exchange of cartographic and associatedtabular data files. Many non-DLG data may be formatted in DLG format.

Digital Map - A machine-readable representation of a geographic phenomenon stored for display or analysis by a digitalcomputer; contrast with analog map.

Digital Orthophoto - A geographically correct digital image with the same accuracy as a vector digital map, butpreserving the information content of the original photography.

Digital Orthophoto Quarter-Quad (DOQ) - a 3.75 minute square distortion free image of the surface of the earth. Theimagery has been geographically and photographically rectified to remove all distortion, and meet requirements of theUSGS.

Digital Terrain Model (DTM) - A computer graphics software technique for converting point elevation data into aterrain model displaced as a contour map, sometimes as a three-dimensional "hill and valley" grid view of the groundsurface.

Dig i t i ze - A means of converting or encoding map data that are represented in analog form into digital information of xand y coordinates.

Digitized Terrain Data - Transposed elevation information from maps or photographs to X-Y-Z digital coordinates forstorage on magnetic media.

Digi t izer - A device used to capture planar coordinate data, usually as x and y coordinates, from existing analogmaps fordigital use within a computerized program such as a GIS; Also called a digitizing table.

D i g i t i z i n g - refers to the process of manually converting an analog image or map or other graphic overlay into numericalformat for use by a computer with the use of a digitizing table or tablet and tracing the input data with a cursor (see alsoscanning).

DIME - Dual Independent Map Encoding Provides vector data such as streets to census data addresses. Superseded byTopologically Integrated Geographic Encoding and Referencing (see TIGER).

DIME File - A geographic base file produced by the U.S. Census Bureau with Dual Independent Map Encoding. Now beingsuperseded by TIGER files (see below).

DLG - See Digital Line Graph

DOB - Division of the Budget

DOQ - See Digital Orthophoto Quarter-quad

DOT - Department of Transportation

DTF - Department of Taxation and Finance

Edge Match - An editing procedure to ensure that all features crossing adjacent map sheets have the same edge locations,attribute descriptions, and feature classes.


Federal Information Processing Standards (FIPS) - official source within the federal government forinformation processing standards. They were developed by the Institute for Computer Sciences and Technology, at theNational Institute of Standards and Technology (NIST), formerly the National Bureau of Standards.

Federal Geographic Data Committee (FGDC) - established by the Federal Office of Management and Budget, isresponsible for the coordination of development, use, sharing, and dissemination of surveying, mapping, and relatedspatial data.

Fifth Generation Computer - A computer designed for applications of artificial intelligence (Al). Some elements ofspatial data management, especially the CADD output side, are beginning to integrate Al computing.

FOIL - Freedom of Information Law

Format - 1. The pattern in which data are systematically arranged for use on a computer. 2. A file format is the specificdesign of how information is organized in the file. For example, DLG, DEM, and TIGER are geographic data sets inparticular formats that are available for many parts of the United States 6File Transfer Protocol (FTP) - a standard protocol that defines how to transfer files from one computer to another.

Fortran - A high-level programming language and compiler originally designed to express math formulas. Developed in1954 by IBM it is still the most widely used language for scientific and engineering programming.

GBF/DIME - See Geographic base file/dual independent map encoding

Geocode - The process of identifying a location as one or more x, y coordinates from another location description such asan address. For example, an address for a student can be matched against a TIGER street network to locate the student'shome.

Geodetic Monumentation - a permanent structure that marks the location of a point taking into account the earth'scurvature.

Geographic - Pertains to the study of the Earth and the locations of living things, humans and their effects.

Geographic Base File/dual Independent Map Encoding (GBF/DIME) - A data exchange format developed bythe US Census Bureau to convey information about block-face/street address ranges related to 1980 census tracts. Thesefiles provide a schematic map of a city's streets, address ranges, and geostatistical codes relating to the Census Bureau'stabular statistical data. See also TIGER, created for the 1990 census.

Geographic Database - Efficiently stored and organized spatial data and possibly related descriptive data.

Geographic Information Retrieval and Analysis (GIRAS) - Data files from the US Geological survey. GIRASfiles contain information for areas in the continental United States, including attributes for land use, land cover, politicalunits, hydrologic units, census and county subdivisions, federal land ownership, and state land ownership. These data setsare available to the public in both analog and digital form.

Geographic Information System (GIS) - An organized collection of computer hardware, software, geographic data,and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographicallyreferenced information. Certain complex spatial operations are possible with a GIS that would be very difficult, time-consuming, or impractical otherwise.

Geographic Object - A user-defined geographic phenomenon that can be modeled or represented using geographic datasets. Examples include streets, sewer lines, manhole covers, accidents, lot lines, and parcels.

Geographical Resource Analysis Support System (GRASS) - 1. A public-domain raster GIS modeling productof the US Army Corps of Engineers Construction Engineering Research Laboratory. 2. A raster data format that can be usedas an exchange format between two GlSs.

Georect i fy - the process of referencing points on an image to the real world coordinates.

Georeference - To establish the relationship between page coordinates on a paper map or manuscript and known real-world coordinates

Geospat ia l - a term used to describe a class of data that has a geographic or spatial nature.

Geostat ionary Sate l l i te : An earth satellite that remains in fixed position in sync with the earth's rotation.

GIS - Geographic information system. A computer system of hardware and software that integrates graphics with databasesand allows for display, analysis, and modeling.

Grid-Cell Data - Grid-cell data entry places a uniform grid over a map area, and the area within the cell is labeled withone attribute or characteristic, such as elevation averaged over all points. Grid cells can be layered with differing types ofinformation.

Global Pos i t ion ing System (GPS) - a system developed by the U.S. Department of Defense based on 24 satellitesorbiting the Earth. Inexpensive GPS receivers can accurately determine ones position on the Earth's surface.

Ground Truth - Information collected from a survey area as remote sensing data is being collected from the same area (seecontrol).

Hierarchical - A way of classifying data, starting with the general and going to specific labels.

Hydrography - Topography pertaining to water and drainage feature.

Hypsography - 1 ) The science or art of describing elevations of land surfaces with reference to a datum, usually sea level.2) That part of topography dealing with relief or elevation of terrain.

Image - A graphic representation or description of an object that is typically produced by an optical or electronic device.Common examples include remotely sensed data such as satellite data, scanned data, and photographs. An image is stored asa raster data set of binary or integer values representing the intensity of reflected light, heat, or another range of values onthe electromagnetic spectrum. Remotely sensed images are digital representations of the earth.

Imagery - a two dimensional digital representation of the earth's surface. Examples are a digital aerial photograph, asatellite scene, or an airborne radar scan.Index - A specialized lookup table or structure within a database and used by an RDBMS or GIS to speed searches fortabular or geographic data.

Infrastructure - The fabric of human improvements to natural settings that permits a community, neighborhood, town,city metropolis, region, state, etc., to function.

Init ial Graphics Exchange Specification (IGES) An interim standard format for exchanging graphics Polygondata among computer systems.'

Internet - a system of linked computer networks, worldwide in scope, that facilitates data communication services such asremote login, file transfer, electronic mail, and newsgroups. The Internet is a way of connecting existing computernetworks that greatly extends the reach of each participating system.

Internet Protocol (IP) - the most important of the protocols on which the Internet is based. It allows a packet totraverse multiple networks on the way to its final destination.

Interpolate - Applied to logical contouring by determining vertical distances between given spot elevations.

IT - Information Technology

Land Information System (LIS) - the sum of all the elements that systematically make information about landavailable to users including: the data, products, services, the operating procedures, equipment, software, and people.

Land Information System (LIS) - NJ State 45:8-28(e) - Any computer coded spatial database designed for multi-purpose public use developed from or based on property boundaries.

Latitude - The north-south measurement parallel to the equator.

Layer- A logical set of thematic data, usually organized by subject matter.

Layers - refers to the various "overlays" of data each of which normally deals with one thematic topic. These overlays areregistered to each other by the common coordinate system of the database.


Longitude - The angular distance, measured in degrees, cast or west from the Greenwich meridian, or by the difference intime between two reference meridians on a globe or sphere.

Lot Number - A numerical parcel designation, that when combined with a block number is unique to a single parcel ofland within a given municipality.

Manual Digitizing - Conversion of an analog measurement into a digital form by using a manual device such as acalculator.

Map - A representation of a portion of the earth, usually drawn on a flat surface. (From Latin mappa, a napkin, sheet orcloth upon which maps were drawn.)

Map Projection - A mathematical model for converting locations on the earth's surface from spherical to planarcoordinates, allowing flat maps to depict three dimensional features. Some map projections preserve the integrity of shape;others preserve accuracy of area, distance, or direction.

Map Units - The coordinate units in which the geographic data are stored, such as inches, feet, or meters or degrees,minutes and seconds.

Metadata - data describing a GIS database or data set including, but not limited to, a description of a data transfer mediums,format, and contents, source lineage data, and any other applicable data processing algorithms or procedures .

NCGIA - National Center for Geographic Information Analysis

Network Analysis - Addresses relationships between locations on a network. Used to calculate optimal routes, andoptimal locations for facilities.

NSGIC - National States Geographic Information Council

NSDI - National Spatial Data Infrastructure

OPRHP - Office of Parks, Recreation and Historical Preservation

ORPS - Office of Real Property Services

Orthophoto - A photograph of the earth's surface in which geographic distortion has been removed.

Overlay - A layer of data representing one aspect of related information.

Parcel - Generally refers to a piece of land that can be designated by number.

Photogrammetry - The system of gathering information about physical objects through aerial photography andsatellite imagery.

Plane-Coordinate System A system for determining location in which two groups of straight lines intersect at rightangles and have as a point of origin a selected perpendicular intersection.

Planimetric Map - A map which presents the horizontal positions only for the features represented; distinguished from atopographic map by the omission of relief in measurable form. The natural features usually shown on a planimetric mapinclude rivers, lakes and seas; mountains, valleys and plains; and forests, prairies, marshes and deserts. The culture featuresinclude cities, farms, transportation routes and public-utility facilities; and political and private boundary lines. Aplanimetric map intended for special use may present only those features which are essential to the purpose to be served.Plat : A scale diagram void of cultural, drainage and relief features, showing only land boundaries and subdivisions togetherwith data essential to its legal description.

Plotter - Equipment that can plot a graphic file using multiple line weights and colors. Types available today are: pen,laser, and electrostatic plotters.

Point Data - level of spatial definition referring to an object that has no dimension, e.g., well or weather station.

P o i n t s - Items such as oil wells, utility poles, etc. Specific objects with exact location noted.

P o l y g o n - A vector representation of an enclosed region, described by a sequential list of vertices or mathematicalfunctions.

Posit ional Accuracy - term used in evaluating the overall reliability of the positions of cartographic features relativeto their true position.

Prec is ion - refers to the quality of the operation by which the result is obtained, as distinguished from accuracy.

Protoco l - a definition for how computers will perform when talking to each other. Protocol definitions range from howbits are placed on a wire to the format of an electronic mail message. Standard protocols allow computers from differentmanufacturers to communicate; the computers can use completely different software, providing that the programs runningon both ends agree on what the data means.

Quadrangle - A four-sided region, usually bounded by a pair of meridians and a pair of parallels.

Quality Control - process of taking steps to ensure the quality of data or operations is in keeping with standards set forthe system.

Raster - A grid-type data format used to interpret gray-scale photographs and satellite imagery. Imagery is stored as dots orpixels, each with a different shade or density.

Raster Data - Machine-readable data that represent values usually stored for maps or images and organized sequentiallyby rows and columns. Each "cell" must be rectangular but not necessarily square, as with grid data.

RDBMS - See relational database management systems.

Recti f ied - referencing points, lines, and/or features of two dimensional images to real world geographic coordinates, tocorrect distortion in the image.

Rectify - The process by which an image or grid is converted from image coordinates to real-world coordinates.Rectification typically involves rotation and scaling of grid cells, and thus requires resampling of values.

Regis trat ion - the procedure used to bring two maps or data layers into concurrence via known ground location controlpoints or the procedure of bringing a map or data layers into concurrence with the earth's surface.

Relational Database Management System (RDBMS) - A database management system with the ability to accessdata organized in tabular files that may be related together by common field (item). An RDBMS has the capability torecombine the data items from different files, thus providing powerful tools for data usage.

Remote Sensing - Recording imagery or data and information from a distance. Photography is a form of remotesensing. Satellites provide a remote sensing platform for developing geology and soils analysis with sensors sensitive tovarious bands of the electromagnetic spectrum.

Resolut ion - 1. The accuracy at which the location and shape of map features can be depicted for a given map scale. Forexample, at a map scale of 1:63,360 (1 inch=1 mile), it is difficult to represent areas smaller than 1/10 of a mile wide or1/10 of a mile in length because they are only 1/1 0-inch wide or long on the map. In a larger scale map, there is lessreduction, so feature resolution more closely matches real world features. As map scale decreases, resolution also diminishesbecause feature boundaries must be smoothed, simplified, or not shown at all. 2. The size of the smallest feature that can berepresented in a surface. 3. The number of points in x and y in a grid (e.g., the resolution of a USGS one-degree DEM is1.201 x 1.201 mesh points).2

Rubber-sheet - A procedure to adjust the entities of a geographic data set in a non-uniform manner. From- and to-coordinates are used to define the adjustment.

SARA - State Archives and Records Administration

Scale - the relationship between a distance on a map and the corresponding distance on the earth. Often used in the form I:24,000, which means that one unit of measurement on the map equals 24,000 of the same units on the earth's surface.


Scanner - A scanner is an optical device that recognizes dark and light dots on a surface and converts this recognitioninto a digital file. However, scanners generally do not create a map database in a logically correct format, so additionalcomputer-aided manipulation and often manual editing are used to add intelligence required by a specific GIS platform.

Scanning - Also referred to as automated digitizing or scan digitizing. A process by which information originally in hardcopy format (paper print, mylar transparencies, microfilm aperture cards) can be rapidly converted to digital raster form(pixels) using optical readers.

Schematic Map - A map prepared by electronically scanning or digitizing in which the lines are not dimensionally orpositionally accurate.

SDTS - Spatial Data Transfer Standard

SED - State Education Department

SEMO - State Emergency Management Office

Server - software that allows a computer to offer a service to another computer. Other computers contact the serverprogram by means of matching client software. Also a computer using server software.

Source Material - data of any type required for the production of mapping, charting, and geodesy products including, butnot limited to, ground-control aerial and terrestrial photographs, sketches, maps, and charts; topographic, hydrographic,hypsographic, magnetic, geodetic, oceanographic, and meteorological information; intelligence documents; and writtenreports pertaining to natural and human-made features.

Spat ia l Data - data pertaining to the location of geographical entities together with their spatial dimensions. Spatialdata are classified as point, line, area, or surface.

Spatial Index - A means of accelerating the drawing, spatial selection, and entity identification by generatinggeographic-based indexes. Usually based on an internal sequential numbering system

Spatial Model - Analytical procedures applied with a GIS. There are three categories of spatial modeling functions thatcan be applied to geographic data objects within a GIS: (1) geometric models (such as calculation of Euclidian distancebetween objects, buffer generation area, and perimeter calculation); (2) coincidence models (such as a polygon overlay); and(3) adjacency models (pathfinding, redistricting, and allocation). All three model categories support operations ongeographic data objects such as points, lines, polygons, TlNs, and grids. Functions are organized in a sequence of steps toderive the desired information for analysis.

Stakeholders - Any constituency in the environment that is affected by an organization's decisions and policies.Standards - In computing, a set of rules or specifications which, taken together, define the architecture of a hardwaredevice, program, or operating system.

State Plane Coordinate System - The plane-rectangular coordinate systems established by the United States Coastand Geodetic Survey (now known as National Ocean Survey), one for each state in the United States, for use in definingpositions of geodetic stations in terms of plane-rectangular (X and Y) coordinates. Each state is covered by one or morezones, over each of which is placed a grid imposed upon a conformal map projection. The relationship between the grid andthe map projection is established by mathematical analysis. Zones of limited east-west dimension and indefinite northsouth extent have the transverse Mercator map projection as the base for the state coordinate system, whereas zones forwhich the above order of magnitude is reversed have the Lambert conformal conic map projection with two standardparallels. For a zone having a width of 158 statute miles, the greatest departure from exact scale (scale error) is 1 part in10,000. Only adjusted positions on the North American datum of 1927 and NAD 1983 may be properly transformed intoplane coordinates on a state system. All such geodetic positions which are determined by the National Ocean Survey aretransformed into state plane-rectangular coordinates on the proper grid, and are distributed by that bureau with the geodetic

positions. State plane coordinates are extensively used in recording land surveys. and in many states such use has receivedapproval by legislative enactment.

SUNY - State University of New York

Sys tem - A group of related or interdependent elements that function as a unit.

Tax Map - An accurate map of a municipal territory prepared for the purpose of taxation. Showing among other things, thelocation and width of streets, roads, avenues and each individual lot of land within the municipality.

Text Data - Information in a GIS system such as property owners' names and lot dimensions.

Thematic Layer - mapping categories, consisting of a single type of data such as population, water quality, or timberstands, intended to be used with base data.

Thematic Map A map that illustrates one subject or topic either quantitatively or qualitatively.

Theme - A collection of logically organized geographic objects defined by the user. Examples include streets, wells,soils, and streams.

TIGER - supersedes DIME (see entry) files.

TIGER - See Topologically Integrated Geographic Encoding and Referencing

Topographic Map - A map of land-source features including drainage lines, roads, landmarks, and usually relief, orelevation.Topologically Integrated Geographic Encoding and Referencing data (TIGER) - A format used by the USCensus Bureau to support census programs and surveys. It is being used for the 1990 census. TIGER files contain streetaddress ranges along lines and census tract/block boundaries. These descriptive data can be used to associate addressinformation and census/demographic data to coverage features.

T o p o l o g y - The spatial relationships between connecting or adjacent coverage features (e.g., arcs, nodes, polygons, andpoints). For example, the topology of an arc includes its from- and to- nodes and its left and right polygons. Topologicalrelationships are built from simple elements into complex elements: points (simplest elements), arcs (sets of connectedpoints), areas (sets of connected arcs), and routes (sets of sections) that are arcs or portions of arcs). Redundant data(coordinates) are eliminated because an arc may represent a linear feature, part of the boundary of an area feature, or both.Topology is useful in GIS because many spatial modeling operations don't require coordinates, only topologicalinformation. For example, to find an optimal path between two points requires a list of which arcs connect to each other andthe cost of traversing along each arc in each direction. Coordinates are only necessary to draw the path after it is calculated .

Transformation - The process of converting data from one coordinate system to another through translation, rotation,and scaling .

Transmiss ion Control Protocol (TCP) - One of the protocols on which the Internet is based.

Vectors - Lines defined by "x", "y" and "z" coordinate endpoints. Roads, rivers, contour lines, etc. presented as vectorlines.

Vector Data - A coordinate-based data structure commonly used to represent map features. Each linear feature isrepresented as a list of ordered x, y coordinates. Attributes are associated with the feature (as opposed to a raster datastructure, which associates attributes with a grid cell). Traditional vector data structures include double-digitized polygonsand arc-node models.

Vector Display : A vector display on a computer screen is produced by drawing vectors on the screen. A raster display, incontrast, is produced on a screen as rows of dots of "on" or "off' which produce the picture.

Wide Area Network (WAN) - a network that uses high-speed, long distance communications networks or satellites toconnect computers over distances greater than those traversed by local area networks (LANs)--about 2 miles.

Workstations and Terminals A workstation is a device or a combination of devices integrated to provide the userwith graphic data entry, display, and manipulation. These devices are used for map digitizing and map-related applications,geographic analysis and ad hoc query. Most systems still use some type of inexpensive edit-query workstations orterminals to provide low-cost access to both maps and related data.


GIS DEVELOPMENT GUIDE: NEEDS ASSESSMENT

11 INTRODUCTION

A needs assessment is the first step in implementing a successful GIS within anylocalgovernment. A needs assessment is a systematic look at how departments function and thespatial data needed to do their work. In addition to the final needs assessment report that isgenerated, intangible benefits are realized by an organization. Conducting a GIS needs assessmentfosters cooperation and enhanced communication among departments by working together on acommon technology and new set of tools. Finally, the needs assessment activity itself serves as alearning tool where potential users in each participating department learns about GIS and how itcan serve the department.

A needs assessment is required if the local government will be adopting a GIS throughout theorganization. Without a complete needs assessment each department might proceed to adopt theirown system and database which may or may not be compatible with those of another department.The largest benefit for a local government adopting a GIS is to realize efficiencies from common"base data" and the sharing of data among departments.

At the conclusion of a needs assessment, an organization will have all of the information needed toplan the development of a GIS system. This information can be grouped into the followingcategories:

• Applications to be developed. - In evaluating the responsibilities and work flow within adepartment, certain tasks are identified that can be done more efficiently or effectively in a GIS.These tasks will form the basis of GIS applications. Application descriptions prepared as partof the needs assessment will describe these tasks.

• GIS Functions required. - For each application identified, certain GIS functions will berequired. These will include standard operations such as query and display, spatial analysisfunctions such as routing, overlay analysis, buffering, and possibly advanced analysisrequiring special programming.

• Data needed in the GIS database. - Most departments in local government use data thathas a spatial component. Much of this data are hardcopy maps or tabular data sets that have aspatial identifier such as addresses and zip codes or X-Y values (latitude-longitude, state planecoordinates, or other coordinate system). A needs assessment will identify how thisinformation will be used by GIS applications.

• Data maintenance procedures. - By looking at the work flow and processes within andbetween departments, responsibility for data creation, updates and maintenance will becomeapparent.

Note: The needs assessment procedure refers to a local government and its departments as the organizational units.In a multi-agency GIS cooperative, the same activities described would be carried out by all participants, at theappropriate level of detail as determined by the role each participant would play in the resulting GIS cooperative.

Needs Assessment 31

Once all of this information is collected and analyzed for each department and published in a report,it can be used as a blueprint for implementing the GIS. The GIS coordinating group within theorganization will use it to:

• Design the GIS database• Identify GIS software that will meet the government's needs• Prepare an implementation plan• Start estimating the benefits and costs of a GIS

A common mistake in performing a needs assessment is to simply take an inventory of the mapsand spatial data currently used in each department. There are two major problems with thisapproach. First, this does not allow the GIS coordinating group to evaluate how a GIS could beused to enhance the work of each department and the agency as a whole . By looking at thedepartment functions and what the department does or produces, the GIS coordinating group andpotential users develop an understanding of the role GIS can play in the organization. The existingdata and maps do need to be inventoried and may well be used in building the GIS, however suchan inventory should be separate from the needs assessment.

The second major problem with the "data inventory" approach is that it tends to focus only on datainternal to the organization. Local governments rely heavily on data from outside sources - federalagencies, state agencies, business, etc. The need for these data is better determined by looking atthe potential GIS applications and how data will be used by each application. It can then bedetermined what data should be acquired from other sources.

22 CONDUCTING A NEEDS ASSESSMENT

The most significant aspect of a needs assessment is to document the findings in a standard andstructured manner. It is very important to adopt (or develop) a standard method to be used for thedescription of all the GIS tasks, processes and data that will be included in the needs assessment.These forms will be used in needs assessment to identify the three kinds of GIS requirements:

• GIS applications - these will be tasks that can be performed by the GIS when a userrequires them, such as preparing a map, processing a query, or conducting some particularGIS analysis. GIS applications can be described using the five page GIS Applications formsincluded with this guide as Appendix A.

• GIS activity - these are situations where information needs to be kept on some activity orprocess important to the user, such as issuing building permits, conducting public healthinspections, etc. A GIS activity can be described using pages 1 and 4 of the GIS Applicationsforms - the main application form and the data flow diagraming (DFD) form.

• GIS data - there will be certain categories of spatial data that are important to keep, but whichwill not appear in any GIS application or activity identified in any application description. Aseparate method must be developed to systematically record the need for such data. Other GISdata needed but not included in either of the above categories, can be entered directly into themaster data list.


The main method used to collect the information to enter onto the forms is individual interviews.Potential users of the GIS can be identified by management and by examination of the organizationchart. A series of one-on-one interviews is the best way to identify the users needs. During theinterview, the user can usually identify documents that can provide additional information to theGIS analyst.

• The needs assessment activity is composed of two main parts• Interviewing and documenting the needs of potential GIS users• Compiling the results of the needs assessment into the master data list and the list

of GIS functions. These two lists respectively are used to prepare the GIS datamodel and the GIS specifications (activities described under Conceptual Design).

The interview process should identify and describe all anticipated uses of the GIS. The nextsection briefly describes the major categories of GIS use, followed by a detailed description onhow to complete the needs assessment forms.

33 LOCAL GOVERNMENT USES OF GIS

The use of geographic information systems by local government falls into five major categories:

• Browse• Simple display (automated mapping);• Query and display;• Map analysis; and• Spatial modeling.

Browse

This function is equivalent to the human act of reading a map to find particular features or patterns.Browsing usually leads to identification of items of interest and subsequent retrieval andmanipulation by manual means. For single maps, or relatively small areas, the human brain is veryefficient at browsing. However, as data volumes increase, automated methods are required toeffectively extract and use information from the map.

Simple Display

This GIS function is the generation of a map or diagram by computer. Such maps and diagrams areoften simple reproduction of the same maps used in a previous manual orientedGIS environment.Examples of this type of use are preparation of a 1:1000-scale town map, a sketch of an approvedsite plan, maps of census data, etc.

Needs Assessment 33

Query And Display

This function supports the posing of specific questions to a geographic database, with the selectioncriteria usually being geographic in nature. A typical simple query would be: "draw a map of thelocation of all new residential units built during 1989" A more complex query might be: "draw amap of all areas within the town where actual new residential units built in 1989 exceeds growthpredictions." Such a query could be part of a growth management activity within the town. Queriesmay be in the form of regular, often asked questions or may be ad hoc, specific purpose questions.The ability to respond to a variety of questions is one of the most useful features of a GIS in itsearly stages of operation. In the long run, other more sophisticated applications of the GIS mayhave a higher value or benefit, but to achieve these types of benefits, users must be familiar withthe GIS and its capabilities. Such familiarization is achieved through the use of a GIS for thesimpler tasks of query and display.

Map Analysis (Map Overlay)

This involves using the analytical capabilities of GIS to define relationships between layers ofspatial data. Map analysis is the super-imposition of one map upon another to determine thecharacteristics of a particular site (e.g., combining a land use map with a map of flood prone areasto show potential residential areas at risk for flooding). Map analysis (often termed overlay ortopological overlay) was one of the first real uses of GIS. Many government organizations,particularly those managing natural resources, have a need to combine data from different maps(vegetation, land use, soils, geology, ground water, etc.). The overlay function was developed toaccomplish the super-imposition of maps in a computer. The data are represented as polygons, orareas, in the GIS data base, with each type of data recorded on a separate "layer." The combinationof layers is done by calculating the logical intersection of polygons on two or more map layers. Inaddition to combining multiple "layers" of polygon-type data, the map overlay function alsopermits the combination of point data with area data (point-in-polygon). This capability would bevery useful in a town for combining street addresses (from the Assessor's files) with other datasuch as parcel outlines, census tract, environmental areas, etc. Many facility siting problems,location decisions, and land evaluation studies have successfully used this procedure in the past.

Spatial Modeling

This application is the use of spatial models or other numerical analysis methods to calculate avalue of interest. The calculation of flow in a sewer system is an example of spatial modeling.Spatial modeling is the most demanding use of a GIS and provides the greatest benefit. Mostspatial modeling tasks are very difficult to perform by hand and are not usually done unless acomputerized system, such as a GIS, is available. These models allow engineers and planners toevaluate alternate solutions to problems by asking "what if" type questions. A spatial model canpredict the result expected from a decision or set of decisions. The quality of the result is only asgood as the model, but the ability to test solutions before decisions have to be made usuallyprovides very useful information to decision makers. Once again, this type of use of a GIS willevolve over time, as the GIS is implemented and used.

A closely related computer capability is a CAD system (computer aided design). CAD systems areused to prepare detailed drawings and plans for engineering and planning applications. While CADsystems functions are different from GIS functions, many commercial CAD products have some of


the functionality normally found in a GIS. There are, however, significant differences between aCAD system and a GIS, mainly in the structure of the data base. There may be some need forCAD-type capabilities in a particular local government, so this forms another category of use.

In general, geographic information in local government is used to:

• Respond to public inquiries,• Perform routine operations such as application reviews and permit approvals, and• Provide information on the larger policy issues requiring action by the town board.

These are typical local government activities which benefit from a geographic information system.The development of GIS will facilitate the present geographic information handling tasks andshould lead to the development of additional applications of benefit to the local government.

There are also other computer systems in local governments that perform GIS-like functions, suchas Emergency 911, underground utility locator systems, school bus routing systems, etc. Thevariety and diversity of GIS applications are what make the definition of a GIS very difficult.Basically, any computer system where the data have one or more spatial identifiers or that performspatial operations can be classed as a GIS. For example, a system containing street addresses andcensus tract codes and that has the ability to place a given street address in the proper census tract isa GIS whether or not map boundaries are part of the system. There are two important points here:

• A large proportion of local government data does have one of more spatial identifiers,and therefore has the potential of being part of a GIS.

• Other, existing systems with GIS data or performing GIS-like functions must beintegrated into the overal system design. GIS should not be developed as a separatesystem.

Whether a local government unit is considering or planning a "full, multi-purpose GIS" or is onlyinterested in a limited or single function system, the database planning and design considerationsare the same. Only the magnitude of the analysis and design activities differ. Some GIS usersbelieve that smaller and simpler applications, such as a school bus routing system, do not require aformal planning activity. There are, however, several reasons to conduct such a planning activityfor the smaller applications:

• To ensure that the user requirements will be fully met

• To develop documentation, especially data documentation (metadata), needed to useand maintain the GIS

• To be in a position to participate in data sharing programs with other agencies asadditional applications are developed

• To create a permanent record of the data and its use to document agency plans anddecisions, and to meet data retention and archiving requirements.

• To use as a base for building a larger, multi-function at some later date.

Needs Assessment 35

The level of effort needed to complete a GIS plan can be kept commensurate with the scope andsize of the intended GIS. Further, the GIS planning software tool that accompanies theseguidelines provides an easy and convenient way to create the recommended documentation.

44 DATA USED BY LOCAL GOVERNMENT

There are many kinds of data used by local government that can be included in a GIS. Data in aGIS can be one of two types: spatial data and non-spatial data. Spatial data is that data which istaken from maps, aerial photographs, satellite imagery, etc. It is composed of spatial entities,relationships between these entities, and attributes describing these entities. Non-spatial data isusually tabular data taken from tables, lists, etc. Most of the time, the non-spatial data will belinked to one or more spatial entities by keys (unique identifiers associated with the spatial data andnon-spatial data). For example, the tax map would represent the spatial data while the real propertyinventory is non-spatial data, which is linked to the entities(parcels) on the tax map.

Spatial data is commonly represented by geometric objects (points, line, and polygons). Non-spatial data containing a spatial reference is also considered spatial data. One of the most commonforms of this type of data in local government are records and files referenced by street address. Examples of local government data that have been used with GIS include:

Tax parcels Land use mapsReal property inventories Zoning mapsInfrastructure data Planimetrics

Water system Right-of-way Sewer system Waterways (streams)

Electric Building OutlinesCensus data Permit records

The operations required in a GIS must meet the data handling requirements of the spatial data aswell as those of the non-spatial data. The most common use of a GIS in local government is thequery based on attribute keys and then displayed in map form.


55 DOCUMENTING GIS NEEDS

The GIS needs are documented using the following forms (full-page sized copies of all forms areincluded in Appendix A):

The GIS Application Description (5 pages) used to:• Describe products (mostly map displays) produced by the GIS• Describe activities supported by the GIS

The Master Data List

Most GIS applications can be described using the GIS Application Description. In cases wherethese forms are not appropriate, any other systematic description of the need can be used. If moreappropriate, different forms can be developed as long as the same information can besystematically recorded: the data required and the GIS functions need to develop the GIS product.

GIS Application Description

The set of forms used to document a GIS contains five pages:

Figure 1 - GIS Application Descriptions

Name of Government

Geographic Information SystemRequirements Analysis


Application Identification #:Application Name:Department:Defined by:

Type of Application:Display Display/Map Scale:Query Query Key:Query & Display Response Time:Map Analysis Frequency:Spatial Model

Data Required: Features (entities): Attributes:

Prepared by: Approved by: Date:

Purpose and Description:

GIS Application Description (Page A- 1)

Use to enter:- Application identification- Description of purpose- Type of application, map scale, query key, frequency, and required response time- Data needed by the application - Entities (features) - Attributes of entites

Needs Assessment 37

Name of GovernmentGeographic Information System

Requirements Analysis

Map Display



Graphical Output Sample: Screen: Hard Copy:

Symbols/Legend

Map Display (Page A- 2)

Used to draw a sample of any maps to be produced by the application (including the legend showing symbols for each feature). This can be a hand sketch, although it should be drawn to the scale of the output desired.



Table Display



Report Layout/Format: Screen: Hard Copy:

HEADINGS

SUB-HEADINGS

SUB-TOTALS/TOTALS:

Table Display (Page A- 3)

Used to show samples of any tables to be produced by the application (used only if tables are needed in the application). If any entries in the table involve complex calculations, these should be described using either a Data Flow Diagram (page 4) or other separate pages.




Data Flow Diagram



Process Description: Data Flow Diagram or Flow Chart

Data Flow Diagram (Page A-4)

Used to draw a data flow diagram or flow chart when an application is complex. This chart is usually drawn by the GIS analyst or someone else familiar with the diagraming techniques, and is used to document complex calculations or descriptions of activities that will need GIS support.



Entity-Relationship Diagram



Data Description: Entity - Relationship Diagram

N

1

1 1

1N

M

Entity-Relationship Diagram (Page A- 5)

Used to draw an entity-relationship (E-R) diagram of the data used in the application. This drawing is usually done by the GIS analyst or someone else familiar with the E-R technique, and is only done for more complex GIS applications.

Needs Assessment 39

66 DOCUMENTING AN ACTIVITY-TYPE USE OF THE GIS

Some GIS applications in local government do not involve the production of maps and tables. Forexample, a GIS may be used to record and store information about a building permit application, asubdivision plat, a site plan, etc. Many activities of local government are simply the processing ofpermits from individuals or firms. If any of these activities will also generate GIS data, they shouldbe described for the needs assessment. Two techniques available for describing processes are flowcharts and data flow diagrams.

A completed application description for a local government activity of this type can be entered onpages 1 and 4 of the GIS Application Description forms. Page 4 - Data Flow Diagram wouldappear as follows:

Data Flow Diagram Example

Zoning Map

TownResident

LocateParcel

DetermineZoning

TownResident

AssessorOffice

PlanningDepartment

LocateParcel

SBL # Index

Tax Map

Figure 2 - Data Flow Diagram Example

This example shows a data flow diagram that has three participants (town resident, planningdepartment, and assessor's department) that uses three parts of the database (zoning map, section-block-lot number index, and tax map), to answer a zoning inquiry. Appendix D contains a briefdescription of the data flow diagraming method.


77 THE MASTER DATA LIST

The master data list is a composite of all data entities (features) and their attributes that have beenentered in the data section of the GIS Application Description (Page 1). Other data identified byusers as "needed," but not included in any application description may be entered directly into themaster data list.

Master Data List

Entity Attributes SpatialObject

--------------------------------------------------------------------------------------------------------------------Street_segment name, address_range LineStreet_intersection street_names LineParcel section_block_lot#, Polygon owner_name, owner_address, site_address, area, depth, front_footage, assessed_value, last_sale_date, last_sale_price, size owner_name, owner_address, assessed_value (as of previous January 1st)Building building_ID, date_built, Footprint building_material, building_assessed_valueOccupancy occupant_name, occupant_address, None occupancy_type_codeStreet_segment name, type, width, Polygon length, pavement_typeStreet_intersection length, width Polygon, traffic_flow_conditions, intersecting_streetsWater_main type, size, material, installation_date LineValve type, installation_date NodeHydrant type, installation_date, Node pressure, last_pressure_test_dateService name, address, type, invalid_indicator NoneSoil soil_code, area PolygonWetland wetland_code, area PolygonFloodplain flood_code, area PolygonTraffic_zone zone_ID#, area PolygonCensus_tract tract#, population PolygonWater_District name, ID_number PolygonZoning zoning_code, area PolygonFigure 3 - Master Data List

Needs Assessment 41

88 CONDUCTING INTERVIEWS

Individual interviews are the most effective way of finding out from users their potential GISapplications. Before starting interviews, a briefing session for all potential users should be held.During this meeting, the interviewers should describe the entire needs assessment procedure to allparticipants. The main activities will be:

• Conduct "start-up" seminar or workshop• Interview each potential user• Prepare documentation (forms) for each application, etc• Review each application description with the user• Obtain user approval of and sign-off for each application description

An introductory seminar or workshop with all potential users in attendance is useful to prepare theway for user interviews. At the beginning of a project, many users may not have much knowledgeabout GIS or how it might help them. Also, the interview team may be from outside theorganization and may not be very familiar with the structure of the particular local government.The start-up seminar should address the following topics:

• Definitions: What is a GIS?How is a GIS used by local government? (Typical applications)

• Interview procedure to be followed:What the interviewee will do?What is expected from the interviewee?Who approves the application descriptions?How the information from the application descriptions will be used?

• Group discussion: It is often useful to have the group identify an initial set of GISapplications as candidates for further documentation. The discussion of possibleapplications between interviewers and users will start to reveal what is suitable for aGIS application. One or more applications can be described in the process by the groupso everyone sees how the process will work.

It is preferable to interview users individually rather than in groups. This provides a betteropportunity to explore the ideas of each person and also prevents other individuals fromdominating any particular meeting. Group meetings easily lose focus on specific GIS applicationsand therefore do not provide the detailed information needed to adequately describe the GISapplications.

Conducting an interview is not an easy task. Some potential users may have a good grasp of GISand how they might use one. However, often potential users do not have complete knowledge ofthe capabilities of a GIS and therefore may not be able to readily identify GIS applications. In thesecases, the interviewer (GIS analyst) needs to help the user explore his/her job activities andresponsibilities to identify GIS opportunities. The GIS analyst should usually begin an interviewwith a review of the procedure, then ask the user to identify and describe potential applications.When specific GIS applications cannot be easily identified, it is helpful if potential users describe,in general, his/her job functions and responsibilities and the role their department plays in thewhole organization. From this discussion, the GIS analyst can usually identify potential GISapplications and then explore these for possible inclusion in the needs assessment.


Needs Assessment 43

How canI use a GIS?

Need to make a mapNeed to answer a query

Need to saveimportant data

Need to describean activity

Prepare Application Description

Add to Master Data ListPrepare DataFlow Diagram



Data Flow Diagram












Master Data List


Street_segment name, address_range LineStreet_intersection street,_names LineParcel section_block_lot#, Polygon

owner_name, owner_address,site_address, area, depth, front_footage, assessed_value,last_sale_date, last_sale_price, size (owner_name, owner_address,assessed_value as of previousJanuary 1st)

Building building_ID, date_built, Footprintbuilding_material, building_assessed_value

Occupancy occupant_name, Noneoccupant_address, occupancy_type_code

Street_segment name, type, width, length, Polygonpavement_type

Street_intersection length, width, traffic_flow_conditions Polygonintersecting_streets

Water_main type, size, material, installation_date LineValve type, installation_date NodeHydrant type, installation_date, pressure Node

last_pressure_test_dateService name, address, type, invalid_indicator NoneSoil Soil_code, area PolygonWetland wetland_code, area PolygonFloodplain flood_code, area PolygonTraffic_zone zone_ID#, area PolygonCensus_tract tract#, populationPolygonWater_district name, ID_number PolygonZoning zoning_code, area Polygon


Figure 4 - Interviewing and Documenting Needs of a Potential GIS User

Needs Assessment 45

99 PREPARING THE NEEDS ASSESSMENT REPORT

The needs assessment report consists of the application descriptions, the master data list, andseveral summary tables. A list of all applications summarizing the type and frequency of use is thefirst table.

App # Application Name Type Frequency1 Zoning Query Query & Display 85 / day2 Customer Phone Inquiry Query & Display 100/day3 Fire Dispatch Map Query & Display 86/day4 Fire Redistricting Map Map Analysis 1/year5 Crime Summary Map Query & Display 12/month6 Patrol Dispatch Map Query & Display 133/day7 Complaint Summary Map Query & Display 624/year8 Subdivision Development Map Query & Display No estimate9 Counter Query Map Query & Display 85/day10 Land Use/Land Value Map Display 1/year11 Assessed Value Map Query & Display 144/year12 Grievance Map Query & Display 2500/year13 Comparable Value Map Query & Display No estimate14 Built/Vacant Map Display 1/year15 Water and Sewer Line Map Query & Display 30/month16 Hydrologic Profile Map Spatial Model 1440/year17 Sewer System Flow Analysis Spatial Model 12/year18 Emergency Repair Map Query & Display 110/year19 Storm Drainage Map Spatial Model 700/year20 Fire Flow Test Map Spatial Model 260/year21 Easement Map Query & Display 520/year22 Zoning Map Query & Display 50/day23 Floodplain Map Query & Display 50/day24 Youth League Residency Check Query & Display 3500/year25 Mosquito Control Area Map Query & Display 50/year26 Site Plan Approval Process Query & Display 200/year27 Census Data Map Display 48/year28 Population Density Map Map Analysis 50/year29 Land Use Inventory Display 24/year30 Retail Space Projection Spatial Model 24/year31 Office Space Projection Spatial Model 12/year32 Traffic Volume Map Query & Display 24/yearFigure 5 List of GIS Applications

This table contains selected GIS applications from the Town of Amherst, N.Y. Needs Assessment


GIS Application by Department by Type

Department Display Query & Display Map Analysis Spatial Model Total

FireDispatch

Police

Assessor

Engineering

Building

Recreation

Highway

Planning

Total

0

0

2

3

2

0

0

10

17

3

4

5

7

2

2

10

12

45

1

0

0

0

0

0

0

3

4

1

0

0

0

0

0

1

3

10

5

4

7

15

4

2

11

28

76

GIS Application by Dept. by Frequency

Department Display Query & Display Map Analysis Spatial Model Total

FireDispatch

Police

Assessor

Engineering

Building

Recreation

Highway

Planning

Total

0

0

2

18

250

0

0

718

988

94,170

49,637

23,894

2,049

25,000

3,520

1,475

2,536

202,281

1

0

0

0

0

0

0

80

81

100

0

0

3,452

0

0

10

40

3,602

94,271

49,637

23,896

5,519

25,250

3,520

1,485

3,374

206,952

Figure 6 - Table Summarizing Applications ExampleThe data from the first table can be used to prepare tables summarizing applications by departmentand the frequency of applications by department.

Numbers in these tables are from the Town of Amherst, N.Y. needs assessment and represent the estimates of GISuse per year. These numbers will be used during the database Planning and Design phase to estimate usage andbenefits, of the GIS. In this example, for the Town of Amherst, it is estimated that 2.5 minutes of staff time will besaved for each query giving a total savings of 4.03 years staff time/year (202,281 times 2.5 minutes divided by 60minutes/hour divided by 2088 hours per year).

The last table relates GIS applications to the data used by each application.Application/Data Item Matrix:

# 1 Leak Detection Map

#2 Customer Service Report

#3 Pressure Test Map

#4 Hydraulic Model Analysis

#5 Work Crew Schedule

Land Parce

ls

RoadsBuil

dings

Water M

ains

Fire H

ydra

nts

Wetla

nd Areas

X X X

X X X

X X X

X

X X X

X

This matrix is very useful in planning and scheduling data conversion. If applications are prioritized, then data needed by high priority applications can be scheduled for conversion early in the conversion process. Also, if some data is not available for some reason, it is possible to determine the affected applications.

Figure 7 - GIS Applications/Data MatrixThe last step in compiling the needs assessment report is to extract the list of GIS functions neededfrom the application descriptions. This list will include the standard function types of display andquery and display plus any other functions included in a data flow diagram or flow chart. Typicalexamples of such GIS functions are: calculate distance between objects, determine the shortest paththrough a network, etc. Figure 8 is an example of a GIS functions list.

Needs Assessment 47

GIS Functions/Procedures List

GIS Functions Needed:

GIS Functions(from Applic. Desc.)

Generic GISFunctions

Candidate GISs

ARC/INFO INTERGRAPH SYSTEM 9

Basic Macro Basic Macro Basic Macro

DISPLAY SCREEN DISPLAY ARCPLOT YES YES

PLOTTER DISPLAY ARCPLOT YES YES

GENERATE REPORT INFO YES YES

QUERY ATTRIBUTE QUERY INFO YES YES

SPATIAL QUERY SPATIAL SEARCH IDENTIFY YES YES

MAP ANALYSIS OVERLAY ARC YES YES

SHORTEST PATH SHORTEST PATH NETWORK NO YES

ROUTE ROUTE NETWORK NO YES

HYDRAULIC AML YES YESMODEL

BUFFER ARC YES YES

RECLASSIFY ARC YES YES

Figure 8 - GIS Function List


ApplicationDescription

List ofImportantData

Data FlowDiagram

Name of Government


Data Flow Diagram









Data Required:

Features (entities): Attributes:



Master Data List

List of GISFunctions

Master Data List


Street_segment name, address_range Line

Street_intersection street,_names LineParcel section_block_lot#, Polygon






Water_main type, size, material, installation_date Line

Valve type, installation_date NodeHydrant type, installation_date, pressure Node


Figure 9 - Compiling Results of Needs Assessment ExampleThe list of GIS functions and the master data list will be used in subsequent tasks to design thedatabase and prepare the GIS specifications.

Needs Assessment 49

1 01 0 SUMMARY

The procedure presented in the guideline for preparing a needs assessment is based ondocumenting GIS applications in a standard format. The components of this format are structuredto facilitate communication between potential GIS users and the GIS analyst, and to providespecific and detailed information to the GIS analyst for designing the GIS. The first page of theapplication description is the most critical to the GIS analyst as it contains the list of data and anindication of the GIS functionality required by the application. If additional information on theGIS functionality is needed, than a flow chart or data flow diagram can be developed (page 4 of theapplication description). For the potential user, the map display and report format describe outputhe/she will receive. These pages should be sufficiently detailed for the user to approve or sign-offas to the correctness of the application description. It is, of course, very important that the entireGIS application description be internally consistent.

The entity-relationship diagram (page 5) is mainly useful in the next phase of the GIS design -Conceptual Design, where the data model for the entire system will be defined. If entity-relationship diagrams are prepared for individual applications, they will than be available for theConceptual Design phase. Otherwise, these diagram can be prepared during the Conceptual Designphase.

Figure 9 is a diagrammetric representation of the flow of information from the elements of theapplication description to the master data list and the list of GIS functions.

Appendix Table of Contents

Appendix A - GIS Application Description Forms

GIS Application Description.............................................................A-1Map Display ...................................................................................A-2Table Display..................................................................................A-3Data Flow Diagram .........................................................................A-4Entity-Relationship Diagram.............................................................A-5

Appendix B

Master Data List.............................................................................. B-1

Appendix C - Sample GIS Application Descriptions

Customer Phone Inquiry, Erie County Water Authority...................... C-1Erie County Map Guide, Erie County Public Works Dept.................... C-4Job Training Site Selection, Erie County Social Services Dept.............. C-5

Appendix D

Data Flow Diagraming.....................................................................D-1

Appendix E

List of Application Name, Type, & Frequency ................................... E-1Application Descriptions .................................................................. E-2Master Data List.............................................................................E-17Summary Table of Depts. & Counts of Application Type....................E-21Summary Table of Depts. & Annual Frequencies of Application Type.E-22









A-1



Map Display



Graphical Output Sample: Screen: Hard Copy:

Symbols/Legend

A-2



Table Display



Report Layout/Format: Screen: Hard Copy:

HEADINGS

SUB-HEADINGS

SUB-TOTALS/TOTALS:

A-3



Data Flow Diagram




A-4



Entity-Relationship Diagram



Data Description: Entity - Relationship Diagram

N

1

1 1

1N

M

A-5

Master Data List


Street_segment name, address_range LineStreet_intersection street,_names LineParcel section_block_lot#, Polygon






Water_main type, size, material, installation_date LineValve type, installation_date NodeHydrant type, installation_date, pressure Node


B-1

Erie County Water AuthorityGeographic Information System


ECWA Geographic Information System

Application Identification #: 19Application Name: Customer Phone InquiryDepartment: Dispatch Defined by: T. May

Type of Application:Display Display/Map Scale: 1" = 100'Query Query Key: AddressQuery & Display XX Response Time: 10 secondsMap Analysis Frequency: xx/daySpatial Model

Data Required:

Features (entities): Attributes:

ROW Location (boundary), street name, street_address_range

Pipe Location (line), size

Parcel Location (boundary), addressBuilding Location (footprint)

Services Location(parcel), address, name, statusProjects Location (boundary), current_in_progressWork_orders Location (parcel_by_address), current,

date work_order_number


Purpose and Description:To respond to phone inquires of: 1) "no water;" or 2) to take requests forservice. (Reference Donohue #18)

C-1




Application Identification #: 19 Application Name: Customer Phone InquiryDepartment: DispatchDefined by: T. May


Graphical Output Sample: Screen: XX Hard Copy:

Symbols/Legend

30 31 1 2 3 4 5 6 7

8

7

6

5

4

3

41

40

39

42 43 44

18

BuildingParcel Water Main

ROW Service Connection

51 ST AVE

Map

le R

oad

C-2




Application Identification #: 19Application Name: Customer Phone InquiryDepartment: DispatchDefined by: T. May


Report Layout/Format: Screen: XX Hard Copy:

Customer Service Inquiry

Name Address Status Pipe Size Project Work Order

J.J. Jones 1551 51st Ave. Active 4 in. None None

C-3

County of ErieGeographic Information System


Erie County Geographic Information System

Application Identification #: 1Application Name: Erie County Map GuideDepartment: Public WorksDefined by: Roger Fik

Type of Application:Display X Display/Map Scale: 1"=2 milesQuery Query Key: N/AQuery & Display Response Time: 5 to 10 minutesMap Analysis Frequency: Yearly publicationSpatial Model

Data Required: Features (entities): Attributes:County Boundary Location, Name (line)Townships Location, Name (Polygon)Cities Location, Name (Polygon)Villages Location, Name (Polygon)Communities Location, Identifier (Node)County Roads Location, Name (Line)City, Town, & Village Roads Location, Name (Line)State Highways Location, Name (Line)Interstate, State Thruway, & Expressways Location, Name (Line)Interstate Route Numbers Route Identifier, LocationState Route Numbers Route Identifier, LocationUS Route Numbers Route Identifier, LocationReservations Location, Name (Polygon)State Parks Location, Name (Polygon)County Parks Location, Name (Polygon)County Forests Location, Name (Polygon)Streams, Rivers, & Creeks Location, Name (Line)Water Bodies Location, Name (PolygonAirports Location, Name (Node)County Jurisdiction Designation Location, Name (Node)

Prepared by J. Volpe: Approved by: Date: 3/15/94

Purpose and Description:To provide a general multi-purpose map of Erie County for public use.

C-4



Erie County Geographic Information Systems

Application Identification #: 48Application Name: Job Training Site LocationDepartment: Social ServicesDefined by: Jeff Embury (C/O Jim Kubacki)

Type of Application:Display Display/Map Scale: MultipleQuery Query Key: Trainee AddressQuery & Display X Response Time: < 1 MinuteMap Analysis Frequency: DailySpatial Model


ROADS XY_Location, Name, Address_Range

TRAINEE Trainee_Address, Trainee_Name

TRAINING SITE Site_Name, Site_Address, Site_Phone #

SUBWAY XY_Location, Subway_Stop_Name,Subway_Stop_Location

BUS ROUTES XY_Location, Busroute_Number,Bus_Stop_Name, Bus_Stop_Location


Purpose and Description: To provide trainees with an adequate training site whileminimizing the distance they must travel to reach that site.

C-5



Erie County Geographic Information System

Application Identification #: 48Application Name: Job Training Site LocationDepartment: Social ServicesDefined by: Jeff Embury/Jim Kubacki

Prepared by: Eric Covino Approved by: Date: 5/5/94

Graphical Output Sample: Screen: X Hard Copy:

Symbols/LegendTrainee Job Training Site Road Bus Subway

C-6



Data Flow Diagram

Application Identification #: 48Application Name: Job Training Site LocationDepartment: Social ServicesDefined by: Jeff Embury (C/O JimKubacki)


Process Description: Data Flow Diagram or Flow ChartStart

Dept. of Social Services

QueryTraineeAddress

OverlayTrainingSites

ChooseTrainingSite

File of Trainee Placement

C-7



Data Flow Diagram

Application Identification #: 48Application Name: Job Training Site LocationDepartment: Social ServicesDefined by: Jeff Embury (C/O Jim Kubacki)



Bus Stop NamesBus Route No.

Bus Stop Coordinates

XY Location

Point

TRAINEE

Line

SUBWAY

Line

ROAD

T

T

Line

BUS ROUTE

T C

Point

JOB SITE

T C

T C

C

C

On

On

XY Location

Name

Address Range

XY Location

Subway Stop Name Subway Stop Coordinates

AddressMatch

AddressMatch

Site Address Site Address

Site Phone #

Trainee Name

Trainee Address

C-8

Data Flow Diagraming

A square represents people, organizations, things,or sources or destinations of data or information

A cylindrical shape to represent a process or activity

An open rectangle to represent a data stored fromwhich data can be added or removed

An arrow to represent data flows. Arrow can beannotated as necessary to describe nature or content flow.

Data flow diagrams offer a standardized method of portraying processes, data stores, andparticipants that make up a logical activity potential GIS application). Four symbols are usedin a data flow diagram:

D-1

List of Application Name, Type, and Frequency

Appl# Application Name Type Frequency11 Subdivision Development Map Query & Display 1 per month12 Counter Query Map Query 50 per day13 Land Use/Land Value Map Display 1 per year14 Assessed Value Map Query & Display 3 per year15 Grievance Map Query & Display 1650 per year16 Comparable Property Map Query & Display 1 per month17 Built/Vacant Map Display 1 per year19 Sanitary Sewer Line Map Query & Display 2 per week28 Public Improvement Map Query & Display 10 per week29 Total Committed Flow Map Spatial Model 20 per week36 Storm Sewer Map Display 10 per day37 Youth League and Residency Check Map Query 1500 per year41 Optimal Snow Removal Route Map Spatial Model 10 per month63 Population Density Map Browse 50 per year70 Population Projection Spatial Model 4 per year

E-1


Application Identification #: 11

Application Name: Subdivision Development Map

Department: Assessor

Defined by: H. Williams


To monitor the progress of development of an approved subdivision (how many lots are built andthe rate of the building).

Type of Application: Display/Map Scale: 100;200;400 Query & Display Response Time:

Frequency: 1 per month

Data Required:Feature Spatial Object

AttributeParcel Polygon

locationStreet (double line) Polygon

namelocation

Subdivision Polygonnamelocation

Prepared by: Approved by: Date: 03-June-96

E-2



Application Name: Counter Query Map




To provide a quick query of one or more parcels and the associated parcel data (mostly ARLM filedata) for answering inquiries at the counter or over the telephone.

Type of Application: Display/Map Scale: 50;100;200;400 Query Response Time:



AttributeBuilding Polygon

assessed valuebuilding #

Parcel Polygonsubdivision lotSBL #location

Street (center line) Linelengthaddress rangenamelocation


E-3



Application Name: Land Use/Land Value Map




To produce a display of the value of land per square foot and/or front footage by land use type.

Type of Application: Display/Map Scale: 200;400 Display Response Time: 1 week

Frequency: 1 per year



depthfront footagesizelast sale priceland use codelocation

Street (center line) Linenamelocation


E-4



Application Name: Assessed Value Map




To produce a map showing the assessed values (by range) for a small area; or for designatedneighborhoods.

Type of Application: Display/Map Scale: 400 Query & Display Response Time: Interactive



AttributeNeighborhood Polygon

namelocation

Parcel Polygonassessed valuelocation

Street (double line) Polygonnamelocation


E-5



Application Name: Grievance Map




To show assessed values of properties in the same area as a parcel where a grievance is filed.

Type of Application: Display/Map Scale: 100;200;400 Query & Display Response Time: interactive




assessed valuelocation



E-6



Application Name: Comparable Property Map




Show the comparable properties selected to determine the assessed value of a given property.

Type of Application: Display/Map Scale: 100;200;400 Query & Display Response Time:




addressassessed valuelocation



E-7



Application Name: Built/Vacant Map




To display the built and vacant parcels

Type of Application: Display/Map Scale: 400 Display Response Time: Interactive



AttributeOccupancy Node

occupant type codeoccupant addressOccupant name

Parcel Polygonbuilt/vacant codelocation



E-8



Application Name: Sanitary Sewer Line Map




To show the location of sanitary sewer lines for the purpose of approving digging activities.

Type of Application: Display/Map Scale: 50;1000 Query & Display Response Time: 5 min.

Frequency: 2 per week


AttributeBuilding footprint Polygon

business namebuilding nameaddress

Manhole Nodedepthlocation

Sanitary sewer line Linelocation

Sidewalk Linelocation

Storm sewer line Linelocation

Street (double line) Polygonnamelocationaddress range

Wye hook ups (new only) Nodedistance from manholeslocation


E-9



Application Name: Public Improvement Map

Department: Engineering

Defined by: P. Bowers


To show facilities near a certain parcel for review of a public improvement permit or site plan.

Type of Application: Display/Map Scale: 100;200 Query & Display Response Time: 30 sec




locationSanitary sewer Line

locationStorm drainage Line

locationStreet (double line) Polygon

curb locationpavement typelocation

Water main Lineinstallation datematerialsizetypelocation


E-10



Application Name: Total Committed Flow Map

Department: Engineer

Defined by: P. Bowers


To keep track of the total committed flow of sanitary and storm sewers.

Type of Application: Display/Map Scale: 1000 Spatial Model Response Time: 1 min



AttributeDetention pond Polygon

capacitysizelocation

Ditches Polygoncapacitysizelocation

Monitoring point Nodelocation

Sanitary sewer line Linecapacitysizelocation

Storm sewer line Linecapacitysizelocation

Street (center line) Linelocation


E-11



Application Name: Storm Sewer Map

Department: Building Department

Defined by: T. Ketchum


To display the location of storm sewers.

Type of Application: Display/Map Scale: 100;200 Display Response Time: 12 sec

Frequency: 10 per day


AttributeContours Line

locationelevation

Easement Polygonlocationtype

Manhole Nodelocationinvert elevationrim/surface elevation

Parcel Polygonlocation

Storm sewer line Linelocation



E-12



Application Name: Youth League and Residency Check Map

Department: Recreation Department

Defined by: J. Bloom


To determine the appropriate league for a resident (by parcel) and discover non-residentapplications.

Type of Application: Display/Map Scale: 1000 Query Response Time: 30 sec



AttributeLeague Polygon

typelocation

Parcel Polygonowner addressowner nameland useaddresslocation


E-13



Application Name: Optimal Snow Removal Route Map

Department: Highway Department

Defined by: F. Jurgens


To calculate the most efficient routes for snow removal and salting.

Type of Application: Display/Map Scale: 1000 Spatial Model Response Time: 1 week



AttributeStreet (center line) Line

lengthclasswidthlocation

Street intersections Nodetraffic flow conditionsstreet names

Traffic zone Polygonareazone code


E-14



Application Name: Population Density Map

Department: Planning

Defined by: G. Black


To browse population density by census tract, block group, or block.

Type of Application: Display/Map Scale: variable: 200 to 1000 Browse Response Time: Interactive



AttributeCensus Block Polygon

block #population totallocation

Census tract Polygontract #location

Parcel Polygonarealand use codelocation

Street (center line) Linenamelocation


E-15



Application Name: Population Projection

Department: Planning

Defined by: C. Brown


To estimate future population of the Town, by small area (census tract, block group, and possiblyblock).

Type of Application: Display/Map Scale: 1000 Spatial Model Response Time: 1 day



AttributeCensus Block Polygon

block #sizelocation

Census tract Polygontract #sizelocation

Net migration Noneapplication #69

Wetland Polygonareawetland code

Zoning Polygonareazoning code


E-16

Master Data List

Feature Attribute Spatial ObjectBuilding Polygon

assessed valuebuilding #

Building footprint Polygonaddressbuilding namebusiness name

Census Block Polygonblock #locationpopultion totalsize

Census tract Polygonlocationsizetract #

Contours Lineelevationlocation

Detention pond Polygoncapacitylocationsize

Ditches Polygoncapacitylocationsize

Easement Polygonlocationtype

League Polygonlocationtype

Manhole Nodedepthinvert elevationlocationrim/surface elevation

Monitoring point Nodelocation

E-17

Master Data List Cont'd

Neighborhood Polygonlocationname

Net migration Noneapplication # 69

Occupancy Nodeoccupant addressoccupant nameoccupant type code

Parcel Polygonaddressareaassessed valuebuilt/vacant codedepthfront footageland useland use codelast sale pricelocationowner addressowner nameSBL #sizesubdivision lot

Sanitary sewer line Linecapacitylocationsize

Sidewalk Linelocation

Storm drainage Linelocation

Storm sewer line Linecapacitylocationsize

E-18

Master Data List Cont'd

Street (center line) Lineclasslengthlocationnamewidthaddress range

Street (double line) Polygonaddress rangecurb locationlocationnamepavement type

Street intersections Nodestreet namestraffic flow conditions

Subdivision Polygonboundaryname

Traffic zone Polygonareazone code

Water main Lineinstallation datelocationmaterialsizetype

Wetland Polygonareawetland code

Wye hook ups (new only)distance from manholes nodelocation

Zoning Polygonareazoning code

E 19

GIS Application by Department by Type

Department Browse Display Query Query Spatial Total& Display Model

Assessor 0 2 1 4 0 7

Building Dept. 0 1 0 0 0 1

Engineering 0 0 0 2 1 3

Highway Dept. 0 0 0 0 1 1

Planning 1 0 0 0 1 2

Recreation Dept. 0 0 1 0 0 1

Total 1 3 2 6 3 15

GIS Application by Department by Frequency

Department Browse Display Query Query Spatial Total& Display Model

Assessor 0 2 18250 1677 0 19929

Building Dept. 0 3650 0 0 0 3650

Engineering 0 0 0 624 1040 1664

Highway Dept. 0 0 0 0 120 120

Planning 50 0 0 0 4 54

Recreation Dept. 0 0 1500 0 0 1500

Total 50 3652 19750 2301 1164 26917

E-20

GIS DEVELOPMENT GUIDE: CONCEPTUAL DESIGN OF THE GIS


PART 1 - DATA MODELING

11 INTRODUCTION

This guide describes data modeling in general, spatial data modeling in specific, the setting ofGISspecifications, and an introduction to spatial data and metadata standards. These activitiesarecollectively called conceptual design of the GIS system (Figure 1). This activity takestheinformation developed during the Needs Assessment and places it a structured format. Theresultof this activity will be a GIS data model and functional specifications for theGIS system.

NeedsAssessment

ConceptualDesign


H/W & S/WSurvey

Pilot/Benchmark








Conceptual design is the first step in database design where the contents of the intendeddatabase are identified and described. Database design is usually divided into three major activities

• Conceptual data modeling: identify data content and describe data at an abstract, orconceptual, level. This step is intended to describe what the GIS must do and doesnot deal with how the GIS will be implemented - the "how" question is thesubject of logical and physical database design;

• Logical database design: translation of the conceptual database model into the datamodel of a specific software system; and

Conceptual Design of the GIS 87

• Physical database design: representation of the logical data model in the schema of thesoftware.





Archives


GIS Database







Database Backups

Figure 2 - Life Cycle of a GIS DatabaseThe conceptual design of the GIS system is primarily an exercise in database design. Databaseplanning is the single most important activity in GIS development. It begins with theidentification of the needed data and goes on to cover several other activities collectively termed the


data life cycle - identification of data in the needs assessment, inclusion of the data in the datamodel, creation of the metadata, collection and entry into the database, updating and maintenance,and, finally, retained according to the appropriate record retention schedule (Figure 2). Acomplete data plan facilitates all phases of data collection, maintenance and retention and aseverything is considered in advance, data issues do not become major problems that must beaddressed after the fact with considerable difficulty and aggravation.

The conceptual design of the GIS also includes identification of the basic GIS architecture(functions ofhardware and GIS software), estimates of usage (derived from the needsassessment), and scopingthe size of the GIS system. All of this is done with reference to theexisting data processingenvironments (legacy systems) that must interface with the GIS.

Preparing A GIS Data Model

A data model is a formal definition of the data required in a GIS. The data model can take one ofseveral forms, the two used in this guideline are a structured list and an entity-relationshipdiagram. The purpose of the data model, and the process of specifying the model, is to ensurethat the data has been identified and described in a completely rigorous and unambiguousfashion and that both the user and GIS analyst agree on the data definitions. Thedata model is then the formal specification for the entities, their attributes and allrelationships between the entities for the GIS.

Building a data model is not necessarily an easy task. Most professionals in local government willnot have had experience in this task. The GIS analyst of the project is the individual who eithershould build the data model or acquire assistance, such as a qualified consultant, to complete thistask. If the opportunity exists for the GIS analyst to attend a database design course or seminar,this would enhance this person's ability to build the model but, more importantly, provide theknowledge for using the final data model in building the GIS. To the extent that data modelsprepared for other local governments match the needs of a particular GIS development program, orcan be easily adapted, they can be modified for use as the data model. However, the GIS analystmust have a good understanding of the resulting model and how it is used to build and manage theGIS database.

The next sections of the guideline first discuss the nature of geographic data, then presentthemethodology used for data modeling, and lastly describe the development of a GIS datamodelfrom the information collected during the Needs Assessment. The example provided in thelast section is actually a sample local government GIS data model and is suitable for direct use,withappropriate modification to specific situations.

22 NATURE OF GEOGRAPHIC DATA


Geographic data describe entities which have a location. The geographic data includes thelocationinformation and other information about the entity of interest. This other information willbereferred to as attributes of the entities. Historically several terms have been used to describethedata in a GIS database, among them features, objects, or entities. The term featurederives fromcartography and is commonly used to identify "features shown on a map," whileentity and object are terms from computer science used to identify the elements in a database.The normal dictionarydefinitions of these terms are:

Object: a thing that can be seen or touched; material thing that occupies space

Entity: a thing that has definite, individual existence in reality

Feature: the make, shape, form or appearance of a person or thing

A good GIS database design methodology requires the use of terms in a clear anunambiguousmanner. This guideline will use the term entity to represent objects or things to beincluded in thedatabase and attribute will be the term for representing the characteristics ormeasurements to berecorded for the entities. Other terms have commonly been used to describethe organization ofentities and attributes in a GIS, such as layer, coverage, base map,theme, and others. Each of thesewill usually refer to a collection of one or more entitiesorganized in some useful way which isspecific to the GIS software in use. These terms willbecome important during the logical/physicaldatabase design activities where decisions abouthow the GIS data are to be stored in the GISdatabase are made. The conceptual database designactivity is focused solely on specifying whatis to be included in the GIS database and shouldprovide clear and unambiguous representation ofthe entire GIS database.

In addition to a clear and concise definition of entities and their attributes, data modeling describesrelationships between entities. An example of a relationship between an employee and acompany would be "works for."

Employee - Works For - Company

Relationships may be bi-directional, thus:

Company - Has - Employees

An important aspect of a relationship is "cardinality," that is if the relationship is between only oneof each entity or if either entity may be more than one. For example, one company usually hasmany employees whereas one employee works for only one company. The possible cardinalitiesare: one-to-one; one-to-many; and many-to-many. Thus:

--- Has --->Company (One) <--- Work For ------ (Many) Employees

There are many variations of the notation used to express these facts. The notation recommendedfor local government will be described later.


Geographic, or spatial data, differs from other "regular" data that are included incomputerdatabases in how entities are defined and in the relationships between entities. Entityidentificationfor spatial data includes the definition of a physical or abstract entity (e.g., abuilding) and thedefinition of a corresponding spatial entity (i.e., a polygon torepresent the building footprint). This latter, or second entity does not exist for other typesof computer databases. The existence ofthe corresponding spatial entity is one of the majorfactors that distinguishes GIS from other types ofsystems and is what makes it very important toutilize proper planning and design techniques whenbuilding a GIS. An example will be used toillustrate this difference.

Entities:Entity:

Physical orConceptual

Entity and Its Attributes

Spatial Entityand Attributes

Parcel (owner_name, owner_address)

Street_segment (name, type, width)

Building (date_built, assessed_value)

Soil-type (soil_code, area)

Landuse_area (land_use, code, area)

Polygon (coordinates, topology)

Line_segment (coordinates, topology)

Footprint (coordinates)

Polygon (coordinates, topology)

Grid_cell (coordinates)

Figure 3 - Examples of Physical or Conceptual Entities and Their CorrespondingSpatial Entities

33 ENTITY-RELATIONSHIP (E-R) DATA MODELING

To start the discussion of entity-relationship modeling, two examples will be shown. One, aregular database and the second, a simple GIS database. The personnel database inany localgovernment could have entities of employee, dependent and department.Relationshipsbetween these entities would be employee " works in" department and dependent "isa member of"the employee's family. Some of the attributes for each entity would be as follows:

Employee (name, age, sex, job title)Dependent (name, age, relationship_to _employee, i.e., spouse, child, etc.)Department (department_name, function, size)

A diagrametric representation of the example would be as follows:


Name

Age

Sex

Name

Function

Size

Employee Works in Department

Has

DependentsOccupant_Name

Unit_Number

Job Title

Name

Age

Relationshlip to employer

Figure 4 - Example of a Firm's Database

An example of a simple spatial database would be a follows:

Parcel ID#, owner_name, owner_address, site_address PolygonBuilding Building_name, height, floor_area FootprintOccupant Occupant_name, unit_number None

The diagrammatic form of this spatial database would be as follows:

Building_Name

Height

Floor_area

Owner_Name

Owner_Address

Situs_Address

Building Located on Parcel

Has

OccupantOccupant_Name

Unit_Number

ID #

Figure 5 - Example of a Simple GIS Database

This example has been presented using two standard notational forms for conceptualdatabasedesign: a relation, the entity name followed by a list of attributes; and an entity-relationshipdiagram showing entities, their attributes, and the relationships between entities.On figure 5, there are two things to notice:

• The standard entity - relationship diagram has no provision for representing thecorresponding spatial entity (point, line, polygon) of the data; and

• The representation of the attributes (ellipses) can be somewhat awkward due todifferent name lengths and the number of attributes to be shown.


The two notational forms modified to accommodate GIS data will be used as the primary tools forconceptual database design in this guideline; however, modifications will be made to adequatelyrepresent GIS data.The next section will provide the formal definition of the basic entity-relationship data modelingmethod, the modifications needed to represent GIS data, followed byexamples of GIS data entities and attributes typical for local government andthe by a descriptionof how to model these data using the modified entity-relationship data modelingtechnique.

Basic Entity-Relationship Modeling

The basic entity-relationship modeling approach is based on describing data in terms of the threeparts noted above (Chen 1976):

• Entities• Relationships between entitles• Attributes of entitles or relationships

Each component has a graphic symbol and there exists a set of rules for building a graph (i.e., anE-R model) of a database using the three basic symbols. Entities are represented as rectangles,relationships as diamonds and attributes as ellipses.

The normal relationships included in a E-R model are basically those of:1. Belonging to;2. Setand subset relationships;3. Parent-child relationships; and4. Component parts of an object.

Theimplementation rules for identifying entities, relationships, and attributes include anEnglishlanguage sentence structure analogy where the nouns in a descriptive sentences identifyentities,verbs identify relationships, and adjectives identify attributes. These rules have beendefined byChen (1983) as follows:

Rule 1: A common noun (such as person, chair), in English corresponds to an entity typeon an E-R diagram.

Rule 2: A transitive verb in English corresponds to a relationship type in an E-R diagram.

Rule 3: An adjective in English corresponds to an attribute of an entity in an E-R diagram.

English statement: Mr. Joe Jones resides in the Park Avenue Apartments which is located on landparcel #01-857-34 owned by the Apex Company.

Analysis: .. "Joe Jones"," "Park Avenue Apartments," "land parcel" and "Apex Company" arenouns and therefore can be represented as entities "occupant," "building," "parcel," and "owner.""resides," "located on" and "owned by" are transitive verbs (or verb phrases) and therefore definerelationships.

Example of Simple E-R diagrams


Building

Resides

Occupant

Located on

Name: Joe Jones

Owned by

Parcel

Owner

Owner_name: Apex Co.

Name ApexCo..

Figure 6 Shows a Simple E-R Diagrams of the Previous Example

Many times it is possible to build different E-R diagrams for the same data. For example, insteadof creating the entity "owner" in the above example, the owner's name could be an attribute ofparcel (shaded areas of figure 6). During the process of building an E-R diagram (i.e., theconceptual model) for a database, the analyst must make decisions as to whether something is bestrepresented as an entity or as an attribute of some other entity.

The process of constructing an E-R diagram uncovers many inconsistencies or contradictions in thedefinition of entities, relationships, and attributes. Many of these are resolved as the initial E-Rdiagram is constructed while others are resolved by performing a series of transformations on thediagram after its initial construction. The final E-R diagram should be totally free from definitionalinconsistencies and contradictions. If properly constructed, an E-R diagram can be directlyconverted to the logical and physical database schema of the relational, hierarchical or network typedatabase for implementation.

Unique Aspects of Geographic Data

In the simplest terms, we think of geographic data as existing on maps as points, lines and areas.Early GIS systems were designed to digitally encode these spatial objects and associate one ormorefeature codes with each spatial feature. Examples would be a map of land use polygons, aset ofpoints showing well locations, a map of a stream shown as line segments. For the purposesofplotting (redrawing the map) a simple data structure linking (x,y) coordinates to afeature codewas sufficient.

Topology

A distinguishing feature of a modern GIS is that some spatial relationships between spatial entitieswill be coded in the database. This coding is termed topologically coding. Topologyisbased on graph theory, where a diagram can be expressed as a set of nodes and links in amannerthat shows logical relationships. Applied to a map, this concept is used to abstract thefeaturesshown on the map and to represent these features as nodes and arcs (point and lines).Nodes are the end-points of arcs and areas are formed by a set of arcs. If the concept anddefinitions of topologic data structures are not familiar to the reader, the following readings arerecommended:


• Geographic Information Systems: A Guide to the Technology, by JohnAntenucci, et. al, pages 98-99.

• Fundamentals of Spatial Information Systems, by Robert Lauring and DerekThompson, pages 206-211.

• ARC/INFO Data Model, Concepts, & Key Terms, by Environmental SystemsResearch Institute, Inc., pages 1-12 to 1-15.

Coordinate strings without topology with associated feature codes were called "spaghetti" filesbecause there was not any relationship between any two coordinate strings formally encoded in thedatabase. For example, the "GIS system" would not "know" if two lines intersect or not orwhether they had common end points. These relationships could be seen by the human eye if aplot were to be made or alternatively could be calculated (often a time consuming process). Typicalof this type of geographic data file are those produced by computer-aided drafting systems (CAD),or known as .dxf, .dwg, or .dgn files.

44 GEOGRAPHIC DATA MODELS

The data models in most contemporary GISs are still based on the cartographic view. Other datamodels have begin to evolve, but are still very limited. Current and potential geographic datamodels include:

• The cartographic data model: points, lines and polygons (topologically encoded) withone, or only a few, attached attributes, such as a land use layer represented as polygonswith associated land used code

• Extended attribute geographic data mode: geometric objects as above but with manyattributes, such as census tract data sets;

• Conceptual object/spatial data model: explicit recognition of user defined objects, zeroor more associated spatial objects, and sets of attributes for reach defined object(example: user objects of land parcel, building, and occupant, each having its own setof attributes but with different associated spatial objects: polygon for land parcel,footprint for building, and no spatial object of occupant).

• Conceptual objects/complex spatial objects: multiple objects and multiple associatedspatial objects (example: a street network with street segments having spatialrepresentations of both line and polygon type and street intersections having spatialrepresentations of both point and polygon type).

Current GIS are based on the cartographic and extended attribute data models. The trend to object-oriented computer systems and databases will require that GIS planners view their databases froman "object viewpoint."

Spatial Relationships


GISs also differ from other systems in that they include spatial relationships. These relationshipsare included in the GIS either by the topologic coding or by means of calculations based on the(x,y) coordinates. One common calculation is whether or not two lines intersect. Table 1 showsthe spatial relationships, associated descriptive verbs, and the common implementation of eachrelationship by a GIS.

Spatial Relationships

Spatial Descriptive Common GIS E-R Model Relationship Verbs Implementation Symbol

Connectivity

Contiguity

Containment

Proximity

Coincidence

Connect, link

Adjacent,abutt

Contained,containing,within

Closest,nearest

Coincident,Coterminous

Topology

Topology

X, Y coord.operation

X,Y coord.operation

X,Y coord.operation

Figure 7 - Spatial Relationships in a GIS

Connectivity and contiguity are implemented through topology: the link-node structure forconnectivity through networks and the arc-polygon structure for contiguity. Containment andproximity are implemented through x,y coordinates and related spatial operations: containment isdetermined using the point-, line-, and polygon-on-polygon overlay spatial operation andproximity is determined by calculating the coordinate distance between two or more x,y coordinatelocations. The spatial relationship of coincidence may be complete coincidence or partialcoincidence. The polygon-on-polygon overlay operation in ARC/INFO™ calculates partialcoincident of polygons in two different coverages. The System 9™ Geographic InformationSystem recognizes coincident features through a "shared primitive" concept (the geometry of apoint or line is stored only once and then referenced by all features sharing that piece of geometry).Future versions of commercial GISs will likely implement coincident features through either the


"belonging to" database relationship or through x,y coordinates and related spatial operations,whichever is more efficient within the particular GIS.

In summary, there are three types of relationships that will be represented in a geographic databasewith an "object view" orientation:

• Normal database relationships, which are represented in a relational database by meansof keys (primary and secondary)

• Spatial relationships represented in the GIS portion of the database by topology

• Spatial relationships that exist only after a calculation is made on the (x,y) coordinates

55 METHODOLOGY FOR MODELING

Modeling a geographic database using the E-R approach requires an expanded or extended conceptfor:

• Entity identification and definition; and• Relationship types and alternate representational forms for spatial relationships.

There are three considerations in the identification and definition of entities in a geographicdatabase:

Correct identification and definition of entities

Entities in a geographic database are defined as either discrete objects (e.g., a building, a bridge, ahousehold, a business, etc.) or as an abstract object defined in terms of the space it occupies (e.g.,a land parcel, a timber stand, a wetland, a soil type, a contour, etc.). In each of these cases we aredealing with entities in the sense of "things" which will have attributes and which will have spatialrelationships between themselves. These "things" can be thought of as "regular" entities.

Defining a corresponding spatial entity for each "regular" entity

A corresponding spatial entity will be one of the spatial data types normally handled in a GIS, e.g.,a point, line, area, volumetric unit, etc. The important distinction here is that we have a singleentity, its spatial representation and a set of attributes; we do not have two separate objects(Figure 3 illustrates this concept). A limited and simple set of spatial entitles may be used, oralternatively, depending on the anticipated complexity of the implemented geographic informationsystem, an expanded set of spatial entities may be appropriate. The corresponding spatial entity forthe regular entity may be implied in the definition of the regular entity, such as abstract entities likea wetland where the spatial entity would normally be a polygon, or a contour where the spatialentity would be a line. Other regular entitles may have a less obvious corresponding spatial entity.Depending on the GIS requirements, the cartographic display needs, the implicit map scale of thedatabase and other factors, an entity may be reasonably represented by one of severalcorresponding spatial entities. For example, a city in a small-scale database could have a point asits corresponding spatial entity, while the same city would have a polygon as its correspondingspatial entity in a large-scale geographic database.


Recognize multiple instances of geographic entities, both multiple spatialinstances and multiple temporal instances

Multipurpose (or corporate) geographic databases may need to accommodate multiplecorresponding spatial entities for some of the regular entities included in the GIS. For example,the representation of an urban street system may require that each street segment (the length ofstreet between two intersecting streets) be held in the GIS as both a single-line street network tosupport address geocoding, network based transportation modeling, etc., and as a double-line (orpolygon) street segment for cartographic display, or to be able to locate other entities within thestreet segment (such as a water line), etc. In each of these instances the "regular" entity is the streetsegment, although each instance may have a different set of attributes and different correspondingspatial entities. Also, there may be a need to explicitly recognize multiple temporal instances ofregular entities. The simple case of multiple temporal instances will be where the correspondingspatial entity remains the same, however, future GISs will, in all likelihood, have to deal withmultiple temporal instances where the corresponding spatial entity changes over time.

Three symbols are defined to represent entities: entity (simple); entity (multiple spatialrepresentations); and entity (multiple time periods). The internal structure of the entity symbolcontains the name of the entity and additional information indicating the corresponding spatialentity (point, line or polygon), a code indicating topology, and a code indicating encoding of thespatial entity by coordinates (Figure 8). The coordinate code is, at the present time, redundant inthat all contemporary GISs represent spatial entities with x,y coordinates. However, it is possiblethat future geographic databases may include spatial entities where coordinates are not needed.Similarly, topological encoding is normally of only one type and can, for the present, be indicatedby a simple code. However, different spatial topologies have been defined and may requiredifferent implementations in a GIS (Armstrong and Densham, 1990). In the future, the topologycode may be expanded to represent a specific topologic structure particular to a GIS application.

G TSpatial Object

Object(entity)

Regular Object Name

Topology Indicator

XY Coordinate Indicator

AssociatedSpatial ObjectType

Figure 8 - Entity Symbol for Spatial Objects


Modeling Spatial Relationships

The spatial relationships are defined by three relationship symbols (Figure 9). The traditionaldiamond symbol can be used for normal database relationships. An elongated hexagon and a doubleelongated hexagon, are defined to represent spatial relationships. The elongated hexagon representsspatial relationships defined through topology (connectivity and contiguity) and the doubleelongated hexagon represents spatial relationships defined through x,y coordinates and related spatialoperations (coincidence, containment and proximity). The appropriate "verbs" to include in thehexagonal symbols are the descriptors of the spatial relationships (as shown in Figure 7). The spatialoperation will be implicitly defined by the relationship symbol (double hexagon), the spatial entityand the topology code. For example, a spatial relationship named "coincident" between entitiesnamed "wetlands" and "soils," both of which carry topologic codes and x,y coordinates, indicates thespatial operation of topological overlay. If this does not sufficiently define the spatial operationneeded, the name of the spatial operation can be used to describe the relationship, such as shortestpath, point-in-polygon, radial search, etc.

Figure 9 shows all symbols needed to construct an Entity-Relationship diagram for a GIS database.

Basic E-R SymbologyE-R Symbology forSpatio-Temporal Data

Entity

Entity: simple withcorrespondingspatial entity

Entity: multiplespatialrepresentation

Entity: multipletemporalrepresentations

Relationship Relationship:represented indatabase

Relationship:representedby topology

Relationship:derived usingspatialoperation

Attribute Attribute

Figure 9 - Extended Entity - Relationship Symbology for DesigningGIS Databases, Source: Calkins, 1996


66 DEVELOPING A SPATIAL DATA MODEL (ENTITY-RELATIONSHIP DIAGRAM)

The information needed to develop the E-R diagram representing the spatial data model comes fromthe Needs Assessment activity as:

• The GIS application descriptions• The master data list: Lists, entities, corresponding spatial entities and attributes• The list of functional capabilities (spatial operations)

The process of building the E-R diagram involves taking entities from the master data list one at atime and placing each one on the diagram. For each new entity, any relationship to any previouslyentered entity should be entered. Relationships are found by examining the ApplicationDescriptions and determining if the GIS processes require a specified operation. For example, ifan Application Description indicated that land parcels needed to be compared to a flood plain area,then a spatial relationship of "coincident area" (or topological overlay operation) should be definedbetween the two entities.

Land Parcel Flood PlainCoincident

AreaPolygon G T Polygon G T

Figure 10 - Diagramming a Spatial Relationship

As each entity is added to the E-R diagram, the list of attributes should be reviewed and checked todetermine if the attribute is appropriate for the entity, does not duplicate any other attribute orentity, and can be rigorously defined for entry to create the metadata (metadata is discussed in thenext section of this guideline).

Figure 11 is a sample E-R diagram for data commonly used by local government. This examplecontains 16 entities and 15 relationships. Attributes have not been included in the diagram in orderto reduce the size of the diagram for inclusion in this document.

100GIS Development Guide

STREETSEGMENT

COINCIDENTAREA

POLYGON G T

WETLANDS

COINCIDENTAREA

COINCIDENTAREA

CONTAINS

HAS

OCCUPANT

ADJACENT

HAS

CONTAINS

WITHIN

LINE G T

WATERMAIN

LINE G T

WATER SERVICECONNECTION

LINK

LINK

LINE G T

COINCIDENTLINE

INTERSECT

NODE G TLINK

ABUTTING

NEARESTADDRESS

HYDRANT

NODE G T

VALVE

NODE G T

STREET SYSTEM

POLYGON G T

FLOODPLAIN

POLYGON G T

SOILS

POLYGON G T

POLYGON G

BUILDING

POLYGON G T

POLYGON G T

POLYGON G T POLYGON G T

POLYGON G T

STREETSEGMENT

POLYGON G T

INTERSECTION

PARCEL

ZONING

CENSUSTRACT

CENSUSBLOCK

TRAFFICZONE

Figure 11 - Entity Relationship Diagram for Selected Local Government Data

77 SUMMARY OF CONCEPTUAL DATA MODELING

The E-R diagram shown in Figure __ will be used to verify with the expected users the datacontent of the GIS and, by additional reference to the GIS needs analysis, the required spatialoperations. Once verified by the users, the E-R representation can be mapped into a detaileddatabase design (as will be described in the Database Planning and Design Guideline)where:

1) Each entity and its attributes map into:(a) One or more relational tables with appropriate primary and secondary keys (thisassumes the desired level of normalization has been obtained);(b) The corresponding spatial entity for the "regular" entity. As most commercial GISsrely on fixed structures for the representation of geometric coordinates and topology, thisstep is simply reduced to ensuring that each corresponding spatial entity can be handled bythe selected GIS package;

2) Each relationship into:(a) Regular relationships (diamond) executed by the relational database system's normalquery structure. Again, appropriate keys and normalization are required for this mapping.(b) Spatial relationships implemented through spatial operations in the GIS. Thefunctionality of each spatial relationship needs to be described, and if not a standardoperation of the selected GIS, specifications for the indicated operation need to be written.

Conceptual Design of the GIS101

PART 2: SPATIAL DATA STANDARDS ANDMETADATA REQUIREMENTS

Introduction

Spatial data standards cover a variety of topics including the definition of spatial data entities(including a formal data model), methods of representation of the spatial entities in a GIS,specifications for the transfer of spatial data between different organizations, and the definition ofthe attributes of the spatial entities and the values these attributes may assume. Metadata is"information about data," and should describe the characteristics of the data such as identifyingentities and attributes by their standard names and provide information on such items as dataaccuracy, data sources and lineage, and data archiving provisions.

Much of the work on spatial data standards to date as been done under the auspices of the FederalGeographic Data Committee and only concerns federal spatial data directly. The relationshipbetween the existing federal data standards and state and local spatial data standards have yet to bedeveloped. Appendix A contains a list of current and pending reports on federal spatial datastandards. Work towards New York State spatial data standards will be conducted under theproposed GIS Standing Committee of the Information Resources Management Task Force.

Metadata for Local Governments in New York State

Metadata can serve many purposes. Some of the more important functions of metadata are:

• Provide a basic description of a dataset

• Provide information for data transfers to facilitate data sharing

• Provide information for entries into clearinghouses to catalogue the availability of data

The metadata structure and content for local government recommended in this guideline has beenprepared according to the following criteria:

• The metadata must first, and primarily, serve as a documentation and data managementtool for the data administrator in an agency or department

• Secondly, the metadata must encompass and support the data manager and recordsmanagement officer in a local agency in all aspects of data management including datadefinition, source documentation, management and updating, and data archiving andretention requirement.

• Thirdly, the metadata information must be able to generate and supply databasedescriptions for spatial data clearinghouses such as the prototype New York StateSpatial Data Clearinghouse developed under the GIS Demonstration Project conductedby the Center for Technology in Government, SUNY - Albany and any relevant federalspatial data clearinghouses.


The following metadata information is a prototype for a New York State Local Government SpatialMetadata Standard. This metadata is represented in a set of tables listed below and has beenimplemented in Microsoft Access™. A working copy of this metadata program is available to alllocal governments in the state. The structure and information on how to use the software aredescribed in a user's guide available with the program. The content of the metadata tables is asshown in the following lists.

Metadata Tables

1. Organization InformationName Of OrganizationDepartmentRoom/Suite #Number And Street NamesCityStateZip CodePhone NumberFax NumberContact PersonPhone Number/ExtensionEmail AddressOrganization Internet AddressComments

2. Reference InformationFilenameFile FormatAvailabilityCostFile Internet AddressMetadata Created ByDate Metadata CreatedMetadata Updated ByDate Metadata UpdatedMetadata Standard NameComments

3. Object/File Name InformationFilenameData Object Name

4. Data Object InformationDistribution Filename (Same as Filename in Reference Information)Data Object NameTypeData Object DescriptionSpatial Object TypeComments


5. Attribute InformationData Object NameData Attribute NameAttribute DescriptionAttribute FilenameCodeset Name/DescriptionMeasurement UnitsAccuracy DescriptionComments

6. Data Dictionary InformationData Object NameData Attribute NameData TypeField LengthRequiredComments

7. Spatial Object InformationData Object NameSpatial Object TypePlace NameProjection Name/DescriptionHCS NameHCS DatumHCS X-OffsetHCS Y-OffsetHCS XminHCS XmaxHCS YminHCS YmaxHCS UnitsHCS Accuracy DescriptionVCS NameVCS DatumVCS ZminVCS ZmaxVCS UnitsVCS Accuracy DescriptionComments

8. Source document informationData Object NameSpatial Object TypeSource Document NameTypeScaleDate Document CreatedDate Digitized/ScannedDigitizing/Scanning Method DescriptionAccuracy DescriptionComments


9. Lineage InformationData Object NameData Object 1Data Object 2Description of Spatial Operation and ParametersAccuracy DescriptionComments

10. Update InformationData Object NameUpdate FrequencyDateUpdated ByComments

11. Archive InformationData Object NameRetention ClassRetention PeriodData ArchivedArchived ByDate to be Destroyed

12. Source DocumentsSource Document NameSource Document ID#Source OrganizationType of DocumentNumber of Sheets (map, photo)Source Material (paper, mylar)Projection NameCoordinate SystemDate CreatedLast UpdatedControl/Accuracy (map, photo)ScaleReviewed byReview dateSpatial extentFile formatComments

13. Entities Contained in SourceSource ID#Entity NameSpatial EntityEstimated Volume of Spatial EntitySymbolAccuracy Description of Spatial EntityReviewed byReview DateScrub Needed (yes/no)Comments


14. Attributes by EntitySource ID#Entity NameAttribute DescriptionCode Set NameAccuracy Description of AttributeReviewed ByReview DateComments

Additional Reading(the following material is quite technical, but a good set of sources on conceptual database design.)

Armstrong, M.P. and P.J. Densham, 1990, Database organization strategies for spatial decisionsupport systems, International Journal of Geographical Information Systems, vol. 4, no. 1, 3-20.

Calkins, Hugh W., Entity Relationship Modeling of Spatial Data for Geographic InformationSystems, International Journal of Geographical Information Systems, January 1996.

Chen, P.P., 1976, The entity-relationship model - toward a unified view of data, ACMTransactions on Database Systems, vol. 1, no. 1, March 1976, pp. 9-36

Chen, P.P., 1984, English sentence structure and entity-relationship diagrams, InformationSciences, 29, 127-149

Davis, C., et. al., eds., 1983, Entity-Relationship Approach to Software Engineering, Amsterdam,Netherlands: Elsevier Science Publishers B.V.

Elmasri, R. and S.B. Navathe, 1989, Fundamentals of Database Systems, Redwood City,California: The Benjamin/Cummings Publishing Company, Inc.

Jajodia, S. and P. Ng, 1983, On representation of relational structures by entity-relationshipdiagrams, Entity-Relationship Approach to Software Engineering, P. Ng and R. Yeh (eds.),Amsterdam, Netherlands: Elsevier Science Publishers B.V., pp. 249-263.

Liskov, B. and S. Zilles, 1977, An introduction to formal specifications of data abstractions,Current Trends in Programming Methodology - Vol. 1: Software Specification and Design, R.T.Yeh (ed), Prentice Hall, pp 1-32.

Loucopoulos, P. and R. Zicari, 1992, Conceptual Modeling, Databases, and CASE: An integratedview of information systems development, New York: John Wiley & Sons, Inc.

Teorey, T.J. and J.P. Fry, 1982, Design of Database Structures, Englewood Cliffs, NJ: Prentice-Hall, Inc.

Ullman, J.D., 1988, Principles of Database and Knowledge-base Systems, 2 vols. (Rockville,Maryland: Computer Science Press, Inc.)


Appendix A

Developing Standards for Spatial Data and Metadata

Spatial data standards are needed in order to facilitate the exchange of spatial data betweengeographic information systems. We refer to data as "spatial" because the common factor is ageographic reference (a reference in space) which allows the data to be accessed through a GIS. Inorder to accomplish the goal of facilitating data exchange, spatial data standards should provide:

• Definitions of terms for spatial objects or features included in GIS;• A structure (or format) for the exchange of spatial data;• A method for describing the accuracy and lineage of the data; and• The definition of metadata (the data that describes the spatial data).

The primary purpose for spatial data standards is to facilitate data sharing and exchange, thus thefocus only on data issues. The Council concluded that It is not necessary to develop standards forGIS hardware or software at this time. as these standards are expected to evolve from groups suchas the Open GIS Consortium, a non-profit trade association formed to implement the OpenGeodata Interoperability Specification .

The Current Status of Standards

At present, spatial data standards exist only at the Federal government level. Under the FederalGeographic Data Committee, three standards documents have been prepared:

The Spatial Data Transfer Standard (SDTS - FIPS 173)

This standard defines a method for the exchange of spatial data between different GIS softwaresystems. It also contains definitions of terms for the spatial objects of interest to Federalgovernment agencies.

Content Standards for Digital Geospatial Metadata (proposed)

This standard defines the content for digital geospatial metadata, the information about spatial datathat would be entered into a clearinghouse or repository to form a catalog of spatial data available toother users.

Cadastral Standards for the National Spatial Data Infrastructure (draft)

This is a draft standard for cadastral (land ownership) data, one of twelve theme standardsdocuments under preparation.The Federal Geographic Data Committee has also established a National Spatial Data Infrastructure(NSDI) for the purpose of coordinating geographic data acquisition and access. The mechanism forthis will be a National Spatial Data Clearinghouse, a distributed network of geospatial dataproducers, managers, and users linked electronically. It is envisioned that this network ofclearinghouses would contain information about available spatial data. Potential users would searchthis clearinghouse to find data of interest, access the metadata for a description of data of interest,and could acquire the data from the distributing agency. Spatial data may be deposited directly witha clearinghouse or retained by the originator.

A-1

Manager's Overview107

The Federal effort towards standards development started in 1981 and The National Spatial DataInfrastructure and Federal spatial data standards are still evolving at this time. The remainingsubject area (theme) standards reports are scheduled for release during the Spring of 1996 ( themesare: base cartographic, bathymetric, cultural and demographic, geodetic, geologic, groundtransportation, international boundaries, soils, vegetation, water, and wetlands). The table belowshows the current status of federal spatial data standards development.Implementation of the Federal geospatial data standards is through Executive Order 12906 signedby the President on April 11, 1994. The FGDC is directed to " ...seek to involve State, local, andtribal governments in the development and implementation of the initiatives continued in thisorder." The Order provides that:

"Federal agencies collecting or producing geospatial data, either directly or indirectly ~e.g. throughgrants, partnerships, or contracts with other entities) shall ensure, prior to obligating funds forsuch activities, that data will be collected in a manner that meets all relevant standards adoptedthrough the FGDC process. "

Status of Federal Geographic Data Committee Standards

Currently in development: Completed public review:

National Spatial Data Accuracy Standard Cadastral Content StandardStandards for Digital Orthoimagery Federal Domain of Values for Data Content StandardDraft Standards for Digital Elevation Data Cadastral Collection Standard (Cadastral)Hydrographic and Bathymetric Accuracy Standard Clearinghouse Metadata Profile (Cadastral)Standards for Geodetic Control Networks Classification of Wetlands and Deepwater HabitatsTransportation Network Profile for of the United StatesSpatial Data Transfer StandardTransportation-related Spatial Feature DictionarySoils Data Transfer StandardVegetation Classification StandardsRiver Reach Standards and Spatial FeatureDictionaryFacility ID CodeContent Standard for Cultural and DemographicData Metadata

Source: Federal Geographic Data Committee Newsletter, November 1995.

A-2



Volume II

Table of Contents

SURVEY OF AVAILABLE DATA

Introduction .....................................................................................1Data Required.....................................................................................1Potential Sources of Data......................................................................1Describing and Evaluating Potential Data...............................................9Reference ...................................................................................13

EVALUATING GIS HARDWARE AND SOFTWARE

Introduction ...................................................................................14Sources of Information About GIS......................................................14

GIS Source Book...........................................................14Publications..................................................................14Trade Shows.................................................................15User Groups.................................................................16

Selection Process...............................................................................17Attachment

A- User Groups ............................................................22

DATABASE PLANNING AND DESIGN

Introduction ...................................................................................24Selecting Sources for the GIS Database................................................25 Master Data List...........................................................................25 List of Surveyed Data Sources .......................................................26The Logical/Physical Design of the GIS Database..................................30Procedures for Building the GIS Database............................................33Procedures for Managing and Maintaining the Database ........................35GIS Data Sharing Cooperatives...........................................................36Matrix Example ................................................................................37

Figures

1 - GIS Representation of Object and Associated Spatial Object ............312 - Example of Mapping of E-R Entity and Attribute List....................313 - E-R Representative of Elements of a Water Distribution System......324 - Physical Design of Several Entities in a Single Layer......................325 - Standard Database Relationship with Primary & Secondary Keys.....336 - Guide to Data Conversion............................................................35

Table of Contents cont'd

DATABASE CONSTRUCTION

Introduction ...................................................................................40Information Required to Support Data Conversion Process....................41Data Conversion Technologies Available..............................................44Data Conversion Contractors..............................................................47Data Conversion Processes .................................................................49Attribute Data Entry..........................................................................54External Digital Data.........................................................................57Accuracy and Final Acceptance Criteria...............................................58

Figures

1 - Steps in Creating a Topologically Correct Vector Polygon Database 402 - Guide to Data Conversion............................................................413 - GIS Data Model..........................................................................414 - Raster GIS Data..........................................................................435 - Vector GIS Data.........................................................................43

PILOT STUDIES AND BENCHMARK TESTS

Introduction ...................................................................................60Pilot Study: Proving the Concept........................................................60Executing the Pilot Study ...................................................................65Evaluating the Pilot Study ..................................................................68Benchmark Tests: Competitive Evaluation...........................................71

Figures

1 - Steps in Creating a Topologically Correct Vector Polygon Database 632 - Guide to Data Conversion............................................................65

GIS DEVELOPMENT GUIDE: SURVEY OF AVAILABLE DATA

11 INTRODUCTION

One of the most important elements of developing a GIS is finding and utilizing the appropriatedata. The form of the data is critical to the overall database design and the success of the analysesperformed with the system. The quality of the results produced from GIS analyses andapplications ultimately resides in the quality of the data used. GIS data can be obtained in variousformats from many different sources. Application requirements based upon quality, scale and levelof completeness will depend upon the needs of the application. Once data requirements aredeveloped, there are usually a plethora of data options which the potential user can choose from.Some of these choices will include whether to utilize government- or privately-developed data, costin this case will be a major difference. Other choices may involve data currency, scale, accuracy,and depending upon the application, the data structure, platform specifications or even mediaformat.

This guideline will discuss various information surrounding available GIS data includingevaluating data requirements, various types and sources of available GIS data, potential datasets.This guideline will also discuss potential opportunities for data sharing.

22 DATA REQUIRED

Master Data List (from Needs Assessment)

One of the products available from a Needs Assessment is a Master Data List. Based upondescriptions of the tasks future GIS users will want to perform, a listing of the various requireddata is developed.

From the Needs Assessment you will have identified:• the data entities• the attributes associated with the entities

The Master Data list is used to prepare a database plan which includes:• a logical/physical design of the GIS database• procedures for building the GIS database• procedures for managing and maintaining the database

In this guide, the procedures for identifying and documenting existing data will be described.

33 POTENTIAL SOURCES OF DATA

Types of Data

There are many different types of data which can be utilized by a GIS system. Each data type hasits own unique properties and potential for contributing to the overall quality and functionality of

Evaluating GIS Hardware and Software 4

the GIS database. These various data types are mapped data, tabular data listings, remotely sensedimagery, and scanned images. The following sections describe these data types.

Mapped Data/Map Series

Mapped data may refer to published maps found in an existing map series or collection. Thesemaps should be logically classified based upon their data content (e.g., topographical, hydrologicaldata). Maps which meet National Map Accuracy Standards are usually produced by federal or stategovernment agencies. Paper maps, if not already in digital format, can be utilized in developingthe database through vector tablet digitizing or scanning.

Mapped data can also be identified as geographic data which has been digitized into the vector datastructure. Vector map data may be found with or without real-world coordinate information andmay or may not have topological relationships. Many organizations which digitized their map datain the past, did so utilizing CAD (computer aided drafting), and thus were not able to establishtopological relationships between their spatial elements. Today, there exists software which allowsCAD data to be quickly converted into topologically correct geographic data which can then beassigned coordinate data within a GIS. Many alternative sources of digital spatial data thus exist,in addition to the volumes of topologically correct geographic data available from local, state andfederal governments.

Attribute Tables or Lists

A readily available form of GIS input, data tables and listings are available from many differentorganizations and government agencies. Various data tables can be obtained as GIS input toprovide additional attributes which will be associated with spatial data elements. These elementsare easily linked using primary relationship keys. Database, spreadsheet or ASCII-delimited texttables include some of the various import formats available in many GIS systems. Anyorganization that maintains a database, or uses spreadsheets to organize their records is able tocreate digital listings. Tables and lists are available from almost any government organization aslong as the data does not involve privacy issues which would impede accessing such data.

Image Data (Remotely Sensed Images, Aerial Photos)

Image data is an excellent source of GIS input data. It mainly consists of remotely sensed imageswhich includes both aerial photographs (in analog or digital format) and satellite images. Aerialphotos are normally captured with analog cameras. These cameras produce photographs whosedata can be very important in a GIS system. Photographs, though not digital, can be digitized byusing a vector digitizing tablet, or they can be scanned, and then input into the GIS as an image. Ineither case, the digital version will normally require rectification and re-scaling in order to correctcamera distortions common with most aerial photography.Until they are converted into a raster GIS format, basic raster images such as satellite imagery orscanned aerial photographs do not offer any topological connectivity or potential for GIS analysis.Satellite imagery is captured in raster digital format. With the advent of an open displayarchitecture, many GIS packages are able to integrate both raster and vector data into the samedisplay. Remotely-sensed image data is useful within an editing environment for display as abackdrop for both heads-up digitizing and updating of vector layers, for verification, or forconversion into raster GIS layers and then subsequently into vector data layers.


Most remote sensing cameras allow for the capture of infrared images, separating different lightwaves into varying band-widths which together and/or alone may show much more informationthan a normal camera reading only in the visible spectrum. Most GIS will allow for the display ofthese images and will allow for the assigning of different colors to the various bands for theeffective display of the data. GIS packages today also allow for the processing of these images inorder to rectify, warp, and geo-reference the imagery as necessary so that they will be useful asscaled images. After such procedures, geo-referenced images can be overlaid with similarly geo-referenced vector imagery for effective display.

Scanned Images (Pictures, Diagrams)

Scanned raster images are able to be displayed in a GIS the same way that satellite images aredisplayed. Any raster image, whether it be a scanned map, photograph or diagram, can be easilyinput into a GIS for display purposes. Integrating scanned images into a GIS display, orconverting raster data into raster GIS format are fairly routine capabilities for most high-end GISpackages. As discussed earlier, a GIS allows for the assignment of coordinates to raster imagedata.

Scanned maps (as opposed to digitized vector representations) can be effective backgrounds uponwhich other GIS vector layers can be displayed. Scanned maps usually contain much valuableannotation which would be very time-consuming to duplicate in a vector environment. Includingraster images allows for the enhancing of an application by providing the user with visual displaydata which can enhance the user's understanding of the data. Scanned photographs are especiallyeffective. In many GIS packages, links can be established between an image viewer, whichdisplays scanned images, and vector geographic features so that when an event sequence isinitiated (e.g. selecting a vector feature), the raster image viewer appears with the specified scannedimage.

Formats

There are three major formats in which GIS-usable data can be obtained. They includehardcopy/eye-readable format, analog image format, and in fully digital format. Unique types ofinformation can be accessed from each of these data formats.

Hardcopy (Paper, Linen Or Film)/Eye-Readable

Hardcopy maps are easily accessed from a wide variety of organizations. Hardcopy maps, as aform of GIS source data, can be digitized on a digitizing tablet into vector GIS format, or scannedand then converted into raster GIS format. Although there are potential accuracy problems whichare associated with paper and linen maps (related to distortions due to shrinkage/expansion of themedia) in capturing geographic features, there is still much unique geographic data which can onlybe found on these maps. An example of unique data from paper or linen maps is seen whenseeking geographic data for a certain time period. Much of the digital data which is readilyavailable may only be the most current, updated data for a region. For example, in order to findgeographic data from before 1970, the only choice may be to access a paper or linen map. Use afilm copy of the source document where available as this will be the most stable media.


Accessing dated tabular information for the development of an attribute database may be a similarendeavor requiring the use of paper documents. Organizations which have been in existence sincebefore the dawn of digital filing systems all had to keep their data in paper "hard-copy" format atone time. Some of these older records may have been converted into digital form at one point. Inother cases, there may be hard-copy documents which are the only versions of dated material. Inorder to conserve space and the integrity of most documents, many might possibly have beencopied onto microfiche.

Image (Picture)

Aerial photography is found to be an abundant geographic data form. Photogrammetry (aerialmapping) is a common way of creating an accurate and up-to-date land base. Aerial photosprovide the raw data which is necessary for various planimetric and topographic mappingapplications. Photographic images are a very rich data source in that many geographic features canbe seen clearly on a photograph but may not be seen in a paper map or a vector digital file (e.g., alarge clearing within a wooded area would not be differentiated on most paper maps, but it isclearly visible on the aerial photo).

Aerial photography is available from many sources (i.e.: USGS, DOT, County agencies, etc.) Thefederal government has recently developed the National Aerial Photography Program (NAPP) inwhich states that desire to have their counties flown may split the cost with the Federalgovernment. Many useful products are derived from the NAPP including 1:12,000 hard or soft-copy orthophotographs. An orthophoto is a scanned aerial photograph which has been digitallyrectified using control points and a digital elevation model. The digital versions are especiallyuseful for GIS applications. If the type of digital aerial photography needed is not available,organizations can create a request for proposal to solicit bids for aerial mapping, although this canbe very expensive.

Digital

Within the digital format genre, there are many different varieties of data available. These variousoptions are becoming as numerous as what is currently available in paper maps. In terms of mapgraphics, there are again two different data structures which are quickly integrated into today's GISsystems: these are raster and vector data formats. Tabular data can be found in digital data formatmost frequently. Various forms of digital spatial data which are currently available in raster formatmay include some of the following:

• Scanned maps and aerial photography• Satellite Imagery• Digital Orthophotography• Digital Elevation Models

Some of the various forms of digital spatial data which are currently available in vector format mayinclude some of the following:

• Topological vector linework• Non-topological vector linework• Annotation layers


Some of the various forms of digital attribute data which can be input into a GIS includes file typesassociated with various software components: spreadsheet, database and word-processing. Someof the file formats which can be utilized include: dBase, Excel, and ASCII delimited text.

Government Sources

Government is the largest single source of geographic data. Data for most any GIS application canbe obtained through federal, state, or local governments. Various data formats, whether paper,image or digital, can all be obtained through government resources. The following subsectionsgive basic descriptions of the datasets which are available through some federal, state andregional/local government agencies.

Federal Data Sources

The federal government is an excellent source of geographic data. Two of the largest spatialdatabases which are national in coverage include the US Geological Survey's DLG (Digital LineGraph) database, and the US Census Bureau's TIGER (Topologically Integrated GeographicEncoding and Referencing) database. Both systems contain vector data with point, line and areacartographic map features, and also have attribute data associated with these features. The TIGERdatabase is particularly useful in that its attribute data also contains census demographic data whichis associated with block groups and census tracts. This data is readily used today in a variety ofanalysis applications. Many companies have refined various government datasets, includingTIGER, and these datasets offer enhancements in their attribute characteristics, which increases theutility of the data. Unfortunately, problems associated with the positional accuracy of thesedatasets usually remain as these are much more difficult to resolve. Satellite and digital orthophotoimagery, raster GIS datasets, and tabular datasets are also available from various data producingcompanies and government agencies.

The following information on federal agencies was taken from the Manual of Federal GeographicData Products developed by the Federal Geographic Data Committee (FGDC). To contact theFGDC:

Federal Geographic Data Committee SecretariatUS Geologic Survey590 National CenterReston, VA 22092Phone 703-648-4533

The departments all have different agencies and bureaus within them which offer various listingson the types of data which are available (e.g. concerning data structure, scale, software exportformat, source data, currency, what applications the data can be used for), and from whichagencies they can be acquired. The reader is encouraged to consult this manual for furtherinformation regarding the geographic data products related to these organizations.


DEPARTMENT OF AGRICULTUREThe Agriculture Stabilization & Conservation Service: RForest Service: B, H, L, Sur, TSoil Conservation Service: H, Sub, Sur

DEPARTMENT OF COMMERCEBureau of the Census: B, S, H, SurBureau of Economic Analysis: B, SNational Environmental Satellite Data & Info. Service: A, Ged, Gep, H, R, Sub, Sur, TNational Ocean Service: Ged, H, R, Sub, Sur, TNational Weather Service: A, R, T

DEPARTMENT OF DEFENSEDefense Mapping Agency: B, H, Sur, T

DEPARTMENT OF HEALTH & HUMAN SERVICESCenters for Disease Control: B, S

DEPARTMENT OF THE INTERIORBureau of Land Management: B, H, L, RBureau of Mines: SubBureau of Reclamation: H, SurMinerals Management Service: B, H, LNational Park Service: B, H, Sur, TUS Fish & Wildlife Service: H, SurUS Geological Survey: A, B, S, Ged, Gep, H, L, R, Sub, Sur, T

DEPARTMENT OF TRANSPORTATIONFederal Highway Administration: Sur

INDEPENDENT AGENCIESFederal Emergency Management Agency: HNational Aeronautics & Space Administration: H, L, R, Sub, SurTennessee Valley Authority: B, S, Ged, H, L, R, Sub, Sur, T

Federal Agency Data Product Code:A = Atmospheric H = Hydrologic Sub = SubsurfaceB = Boundaries L = Land Ownership Sur = Surface and Manmade FeaturesGed = Geodetic R = Remotely Sensed T = TopographyGep = Geophysics S = Socioeconomic

National Spatial Data Infrastructure (NSDI)

There is a wealth of geographic data which can be accessed from federal and state agencies over theinternet. Most federal agencies which deal with geographic data have File Transfer Protocol (FTP)servers storing various geographic datasets. These servers allow organizations to download digitaldata over the internet. One of the most populated servers is the US Geological Survey FTP server,which holds all of the USGS Digital Line Graph files (the USGS server FTP address can be found


by calling the USGS at 1-800-USA-MAPS). The Census Bureau also has an FTP server whichallows organizations to access portions of its TIGER/Line file database. Government FTP serverscan be searched for on the internet using ARCHIE.

Many federal and state agencies and corporations which deal with geographic data have internethome pages which can be accessed on the World-Wide-Web. The US Geological Survey (USGS)home page (URL address: http://www.usgs.gov), like the USGS FTP server, contains a wealthof information about USGS geographic data and how it can be used. From the USGS home pageit is possible to search for, view, and download USGS data. One can also obtain USGS FactSheets, general information on the USGS, educational resources, publications, research papers,and informational resources on other internet sites. Most federal agencies have their own homepage and are structured similarly to the USGS home page. Most major GIS software vendors alsohave internet home pages. Environmental Systems Research Institute (ESRI), Inc. has an excellenthome page (URL address: http://www.esri.com) which contains a wide assortment of usefulinformation.

State Government Agencies

There are many New York State agencies which are good sources of GIS data. Three of theseorganizations include the Department of Transportation, the Department of EnvironmentalConservation, and the Office of Real Property Services.

The New York State Department of Transportation (NYSDOT) offers data in paper and digital fileformats. Paper topographic maps can be obtained at various scales. Most applicable to GISneeds, the NYSDOT has developed digital spatial files which are part of the New York StateCounty Base Map Series. The Base Map files, though created with a CADD (Computer AidedDesign and Drafting), have been designed for use in a GIS. The Department has developed a filestructure which will allow for their conversion into a topological GIS format. There are variousdata layers available within this database including: Roads, Boundaries, Hydrography,Miscellaneous Transportation, and Names (NYSDOT, 1994). For further information, see DigitalFiles from the County Base Map Series from the NYSDOT.

The New York State Department of Environmental Conservation (NYSDEC) is another stateorganization which offers GIS data in varying formats. In 1990, the NYSDEC compiled an in-house inventory of its geographic data sources called the "Geographic Data Source Directory. Thedirectory contains information on all of the DEC's geographic data sources with potential GISapplications. The DEC divided its data into the following categories: Air Resources, ConstructionManagement, Fish and Wildlife, Hazardous Substances Regulation, Hazardous WasteRemediation, Lands and Forests, Law Enforcement, Management Planning and InformationSystems Development, Marine Resources, Mineral Resources, Operations, Regulatory Affairs,Solid Waste, and Water (Warnecke et al, 1992). A copy of the directory is available fromNYSDEC. Call your local office or the main office in Albany.

The New York State Office of Real Property Services (ORPS) has developed a database known asRPIS (Real Property Information System) which contains information on all tax parcels in thestate. Each parcel contains a coordinate representing the center point of the parcel and attributeinformation which includes: unique land-based parcel identification numbers and descriptiveinformation, such as land use, locations, sales information, exemptions, and other parcel


attributes. RPIS data is available to local assessors, real property assessment offices , corporationsand the general public for a nominal fee.

The New York State Department of Health (DOH) uses GIS in its work in analyzing and mappingenvironmental health risk areas and hazardous waste sites. The DOH has a database containingCensus Bureau TIGER files and parcel maps. These GIS files can be acquired by the public.

Some other agencies which have GIS databases and which may have data usable in a GIS include:the Adirondack Park Agency (APA); the Hudson River Valley Greenway; New YorkMetropolitan Transportation Council; the Office of Parks, Recreation and Historic Preservation;Department of Public Service; State Emergency Management Office; New York City Departmentof Environmental Protection (Hilla, 1995); State Data Center Affiliates (various NYS Counties).Please note these are all examples and not intended to be an exhaustive list.

Regional And Local Governments

Many regional and local government agencies and organizations maintain GIS databases. Theseagencies may have data sharing arrangements with local companies and other municipalities.Information identifying which government agencies and companies have available GIS data layersmay be found in regional or local GIS data directories. One such regional data directory developedwithin New York State is the Regional Directory of Geographic Data Sources for Genesee/FingerLakes Counties. The directory contains information on participating government agencies andcompanies which have GIS data layers, then lists information regarding these layers, and providesthe name, address and phone number of the person within the organization who can be contactedfor further details or data sharing arrangements (GIS/SIG, 1995).

Private Data Firms

There are companies that will develop data for a local government. These companies will developprograms based on contract data conversion or public/private partnerships. Contract dataconversion firms are available for those organizations that wish to have custom geographic datasetsdeveloped. Usually, the development of these datasets involves the client organization providingexisting source data (e.g., paper maps) to the data development firm, which then converts the datainto digital format.

In public/private partnerships, the company will work out an agreement with the local governmentthat will provide data conversion but also retain the ability to market, sell and/or use the digital datathat was created. Public/private agreements are just emerging as a method for creating GISdatabases cost effectively. When considering a public/private partnership, issues such asownership, access, freedom of information requirements and long-term data maintenance must beaddressed as well as the cost sharing of building the database.

44 DESCRIBING AND EVALUATING POTENTIAL DATA


The next step is to actually survey the various departments within the local governments and otherexternal sources to determine what data is available for use in the GIS and what “condition” thedata is in.

Metadata Documentation

The first step will be to document the data by developing metadata files for each database available.The metadata file is used for two roles. 1) develop information that will be used to evaluate the datafor use in a GIS and 2) fulfill the metadata requirements for data once it is used in a GIS.

For each potential data source for the GIS database, the map series, photos, tabular files, etc. justbe identified, reviewed, and evaluated for suitability to use in the GIS. Maps, photos, andremotely sensed data are the most likely sources and should be evaluated for:

• appropriate scale• projection and coordinate system• availability of geodetic control points• aerial coverage• completeness and consistency across entire area• symbolization of entities (especially positional accuracy of symbol due either to size of

symbol or off-set placement on map)• quality of linework and symbols• general readability and legibility for digitizing (labels)• quality and stability of source material (paper/mylar)• amount of manual editing needed prior to conversion• edge match between map sheets• existence and type of unique identifies for each entity (often entities shown on in map

series used so-called "intelligent" keys or identifiers where an identifier for an objectcontains the map sheet number and/or other imbedded locational codes - in databasedesign, it is much better to avoid "intelligent" keys of this type, particularly locationalcodes).

• positional and attribute accuracy

All of the above information needs to be documented for each potential data source. If a particulardata source is then used to build part of the GIS database, some of this information will becomepart of the permanent metadata.

The metadata software accompanying this guideline provides three tables for recording the basicmetadata about a potential data source. The content of these tables is listed below. The first tablecontains information on the source document (or file); the second table can describe each entitycontained on a source document; and the third table can describe each attribute of an entity. Onceagain, only the most basic entries have been included in the supporting software in order to keepthe software simple an straightforward. A particular user may wish to expand the tables providedto meet his/her specific needs.






Archives


GIS Database







Database Backups

Figure 1 - Life Cycle of a GIS Database: Source Documents


The following lists the fields of the three tables that contain source data information:

Source Documents

Source Document Name: Parcel Map

Source ID #: 1

Source Organization: Town of Amherst

Type of Document: Map

Number of Sheets (map, photo, etc): 200

Source Material: Mylar

Projection Name: UTM

Coordinate System: State Plane

Date Created: 5-Oct-91

Last Updated: 8-Nov-95

Control Accuracy Map: National Map Accuracy Standard

Scale: Variable; 1" = 50 ft To 1" = 200 ft

Availability: Current

Reviewed By: Lee Stockholm

Review Date: 19-Dec-95

Spatial Extent: Town of Amherst

File Format: N/A

Comments:


Entities Contained In Source

Source ID #: 1

Entity Name: Parcel

Spatial Entity: Polygon

Estimate Volume Spatial Entity: 126 per map sheet

Symbol: None

Accuracy Description Spatial Entity: National Map Accuracy Standard


Review Date: 02-Jan-94

Scrub Needed: Yes

Comments:

Attributes By Entity

Source ID #: 1

Entity Name: Parcel

Attribute Name: SBL Number

Attribute Description: Section, Block, and Lot Number

Code Set Name: N/A

Accuracy Description Attribute: N/A

Reviewed By: John Henry

Review Date: 08-Feb-93

Comments:

Additional Criteria For Evaluating Potential Data Sources

As the survey is being conducted, it is important to consider the following issues about the data:• Is the data current and what is it’s continuing availability?• Is the data suitable for intended applications?• Is the quality of the data appropriate for the type of applications needed? This

should include both locational and attribute accuracy.• Is the data cost effective?


FOR FURTHER INFORMATION:

The Manual of Federal Geographic Data Products, developed by the Federal Geographic DataCommittee, is an excellent source for information on geographic datasets produced by agencieswithin the federal government. Listed by federal agencies and bureaus within each federaldepartment, there are listings on the types of data which are available (e.g. concerning datastructure, scale, software export format, source data, currency, what applications the data can beused for), and from which agencies they can be acquired.

To order contact:Federal Geographic Data Committee SecretariatUS Geologic Survey590 National CenterReston, VA 22092Phone 703-648-4533

New York State Department of Transportation data listing: Digital Files from the County BaseMap Series.

Map Information SectionMapping and Geographic Information Systems BureauNew York State Department of TransportationState Office CampusBuilding 4, Room 105Albany, New York 12232Phone: (518) 457-3555

Example of a Regional Level GIS Data Directory:

1995 Regional Directory of Geographic Data Sources, developed by the GIS/SIG (GeographicInformation Sharing/Special Interest Group) for New York State's Genesee/Finger Lake RegionCounties. The directory is a listing of the various data sources which are available from localcompanies, and local government agencies in the Genesee/Finger Lakes Region.

The International GIS Source book, published by GIS World, Inc. is an annual publication whichcontains an excellent "Data Source Listings" chapter. It provides a wealth of information oncompanies which produce GIS datasets and also provides descriptions of the data they produce.The chapter also lists the different types of spatial data produced by public agencies, and lists dataavailability and contacts.

REFERENCE

Hilla, Christine M. "The Revolution of Geographic Information Systems in Land Use andEnvironmental Planning in New York State," Environmental Law in New York, Vol 6, no. 3.,March, 1995.

Montgomery, Glenn E. and Harold C. Schuch, 1993. GIS Data Conversion Handbook. FortCollins, CO: GIS World, Inc., pp. 89-91.

NYSDOT (New York State Department of Transportation), Digital Files from the County BaseMap Series, mapping and Geographic Information Systems Bureau (1994).

Warnecke, L., J. Johnson, K. Marshall and R. Brown, State Geographic Information ActivitiesCompendium, 294 Council of State Government (1991).


GIS DEVELOPMENT GUIDE: EVALUATINGGIS HARDWARE AND SOFTWARE

11 INTRODUCTION

Purpose of Guide

A GIS is more than just hardware and software. It is a complex system with multiple components:Hardware, Software, People, Procedures and Data. The purpose of this guide is to focus on thehardware and software components of the system and how to acquire information on what isavailable.

Deciding what hardware and software to use for your GIS is a difficult yet important task. It willmake up the foundation on which you will build your system. There is no clear-cut formula to useto make the selection process easier. In this guideline we will give you suggestions that you canuse to evaluate various systems and sources for additional information.

22 SOURCES OF INFORMATION ABOUT GIS

To develop an understanding of GIS, you will need to get information about GIS systems. Here isa sampling of references to start with. This is not a comprehensive listing. Use it as a starting pointand spread out from there.

GIS Source Book

The GIS source book is a good reference book that will give you a great deal of information aboutsoftware vendors, trade associations, product specifications and more. This book is published by:

GIS World, Inc.155 E. Boardwalk Drive, Suite 250Fort Collins, CO 80525Phone: 303-223-4848Fax: 303-223-5700Internet: [email protected]

Other Publications

Conference ProceedingsEach major GIS conference publishes the proceedings from their event. Contact theassociation listed in Attachment A for information on how to obtain these documents.Scholarly Journals


There are a number of scholarly journals that deal with GIS. These are published on an on-going basis.

Cartographica - Contact: Canadian Cartographic AssociationCartography and Geographic Information Systems - Contact: American

Cartographic AssociationInternational Journal of Geographical Information Systems - Contact: Keith Clark at

CUNY Hunter College, New York CityURISA Journal - Contact: Urban and Regional Information Systems Association

Trade Magazines

There are a number of trade magazines that are focused on GIS. They are:

GIS WorldGIS World Inc.155 E. Boardwalk DriveSuite 250, Fort Collins, CO 80525Phone: 303-223-4848Fax: 303-223-5700Internet: [email protected]

Business GeographicsGIS World, Inc.155 E. Boardwalk Drive, Suite 250Fort Collins, CO 80525Phone: 303-223-4848Fax: 303-223-5700Internet: [email protected]

Geo Info SystemsAdvanstar Communications859 Williamette St.Eugene, OR., 97401-6806Phone: 541-343-1200Fax: 541-344-3514Internet:[email protected] site:http://www.advanstar.com/geo/gis

GPS WorldAdvanstar Communications859 Williamette St.Eugene, OR., 97401-6806Phone: 541-343-1200Fax: 541-344-3514Internet:[email protected] site:http://www.advanstar.com/geo/gis

Association Newsletters


Many associations have newsletters that cover GIS topics and can be a good source ofinformation. Contact the organizations listed in attachment A for more information

Books with vendor specific information

There is a number of books published about GIS and related topics. Here are some of thepublishers:

Onword Press2530 Camino EntradaSante Fe, NM, 87505-4835Phone: 505-474-5132Fax: 505-474-5030

John Wiley & Sons, Inc.605 Third AvenueNew York, NY, 10158-0012

ESRI, Inc.80 New York StreetRedlands, CA 92373-8100Phone: 909-793-2853Fax: 909-793-4801

GIS World, Inc.155 E. Boardwalk Drive, Suite 250Fort Collins, CO 80525Phone: 303-223-4848Fax: 303-223-5700Internet: [email protected]

Vendor Booths at Trade Shows

A wealth of information is available at trade shows from vendor booths. These can range from thegeneral product literature to white papers and technical journals. This is also a good time to gather alarge amount of information on different companies in a short period of time.

User Groups

User Groups are another source of valuable information and support. There are a number of usergroups that have formed to provide support and professional networking. GIS user groups areformed around a geographic region or by users of specific software products. New users arealways welcome to these groups. A listing of users groups is contained in Attachment ACurrent Users

The best way to gauge a vendor is by talking to their installed sites. The information that you getfrom talking to these users will be valuable insight into the type of company you will be workingwith. Ask the vendors you want to explore for a list of all of their users in the area or that aresimilar to your organization. Ask for contact names and phone numbers/e-mail addresses.


33 SELECTION PROCESS

Initially you will need to evaluate the software independently of hardware. The software will beselected based on the functionality it offers. Your hardware selection will be based on the GISsoftware you select and the operating system strategy your organization uses. You will need to testthe hardware and software together making sure it works as advertised.

The nature of hardware and software technology is that it changes. In recent years it has beenchanging very quickly. Don't let this stop your efforts. It is easy to get intimidated. The importantthing to remember is to get a product that has been proven in the marketplace and continues to havea clear development path. Avoid technology that is outdated or is on the bleeding edge and has notbeen proven.

Software

Software is evaluated on functionality and performance. In the Needs Assessment guide the needto identify the functionality was discussed. Here is where you will begin to use this information.

Functionality

What is important here is the ability of the software to do the things you need it to do in astraightforward manner. As an example, if the intended users are relatively new to usingcomputers, the software has to have an easy to use graphical user interface (GUI). If theorganization needs to develop specific applications, the software should have a programminglanguage that allows the software to be modified or customized.

In the Needs Assessment Guide, the final report contains tables and references to the functionalityyou will need. Use this in developing the overall functionality required for the system.

Standards

Standards are a way of making sure that there is a common denominator that all systems can use.This can be in the form of data formats that can import and export data into the system, guidelinesused for developing software, supporting industry developed standards that allow differentapplications to share data. Standards are generally developed by a neutral trade organization or insome cases are defined by the market.There is a group that has formed for the GIS industry called Open GIS. This organization isdeveloping standards for developers to use as they engineer software. Open GIS is made up ofrepresentatives from the software developer companies.

Performance

The performance of the software is dependent on two factors, 1) how it is engineered and 2) thespeed of the hardware it is running on. GIS software is complex and will use a large amount of thesystem resources (memory, disk, etc.). The more complex the software, the more resources it willneed.


Performance will be impacted if you have a minimally configured computer. Look for thedeveloper’s software specifications to see what configuration is needed to run the software. Thiswill give you the minimum requirements. Follow this up by getting the recommendedspecifications from the developer or a user group. These recommendations will give you a moreaccurate idea of the type of configuration you will need.

Expandability

The software needs you have today will change over time. More than likely your system will needto expand. Is the software being evaluated able to provide networking capabilities? Will it sharedata with other applications? Will it grow as the organization's GIS grows? Evaluate softwarebased on the ability to grow with you. This may mean that there are complimentary products thatcan be used in conjunction with the package you are evaluating today or the developer has clearlydefined plans for added functionality. Talk with other users to see if the developer has a good trackrecord for providing these enhancements.

Licensing

GIS software is not purchased, it is licensed. There is normally a one-time license fee with an on-going maintenance fee that provides you with the most current versions of the software as they arereleased. In large systems this will be spelled out in a licensing agreement with a correspondingmaintenance agreement. For desktop software a shrink wrap license is used with subsequentreleases being offered to existing users through a discounted upgrade. The maintenance fees andupgrade costs generally run between 15% to 30% of the initial license fee.

The terms in most software packages spell out how the software can and cannot be used. Have theterms of the license reviewed by an attorney before signing up. This can save hassles later as youare developing and using your system.

Hardware

When discussing hardware, there are terms/concepts that you need to understand. The following isa discussion of these. However, GIS software selection drives the hardware requirements.Therefore before launching a full scale evaluation of hardware, make your selection for the GISsoftware you will be using.Hardware can be broken down into the following basic components:

Operating SystemProcessorDiskMemoryCommunications

Operating Systems

An operating system is the software that runs the computer hardware. It is this program that tellsthe computer what to do and how to do it. You may already be familiar with some of the operating


systems that are on the market such as Microsoft’s Windows product or various brands of theUNIX operating system.

It is important to have an Operating System plan within your organization. The plan should takeinto account the departments that will be using the computer system, the type of network beingused (or being planned), what operating systems are currently being used, how large the databaseis and what kind of technical support skills you have access to (in-house or contractor).

The GIS will need to fit into your operating system plan. This will be important as you add otherdepartments onto the system.

Processor

The processor or CPU (central processor unit) is the part of the computer that actually does thecalculations or “processes” the instructions being sent to it. The most common term that describethe processor’s capabilities is the clock speed. This is stated in terms of MHz (MegaHertz). Theclock speed simply describes how many cycles per second the processor works. The higher theclock speed the faster the processor.

Another description of the processor’s capability is how many bits it can access at one time. Manyof the new processors are 32-bit processors. This means that the CPU can access or “grab” 32 bitsof information during each cycle. Older computers such as a “386” machine where 16-bitmachines. There are some machines on the market that manufacture a 64-bit machine (such asDigital Equipment Corporation). These are very fast CPU’s but are hampered by the lack of a 64-bit operating system that can take advantage of it’s speed. It is the direction the hardware industryseems to be heading.

Disk

The disk or hard drive is the device used to store the operating and application software. It is alsoused to store data and images. In working with a GIS you will quickly find out that GIS uses alarge amount of disk space. It is not uncommon to have multiple gigabytes of hard drive on asingle end-user machine and 10 - 20 gigabytes on a central data server. Luckily the prices of harddrives have been coming down and will continue to be affordable.

Memory

Memory or random access memory (RAM) is used as a temporary storage space by the operatingsystem and by the application software which is running on the computer. Most applications runbetter as the amount of memory increases. This is true up to a point. At some point, theperformance increases will begin to taper off as additional memory is added. Most softwaredevelopers can give you configuration data that indicates where this point is.

Communications

The trend in most systems today is to link up users throughout the organization on a network. Thisis an area in the computer industry that is advancing very rapidly. It is recommended that you retaina competent consultant who works with networks to give you detailed and current information.


In simple terms, a network is a connection between computers that allows information to be passedaround from computer to computer. In a typical organization, this is a local area network (LAN).In order to connect a computer to the network it will need a network card for the wiring to plug intoand network software to allow the computer to transmit and receive signals over the wiring. Ofcourse the physical network (wiring) is also needed.

A small network within a department is inexpensive and can allow the users to share networkresources such as printers and database servers. The network can provide services like e-mail anddisk sharing. It can also be the entryway into larger networks that go outside the building orcampus your organization is located on. This is called a Wide Area Network (WAN). A WANrequires a more structured network architecture. It does give users access to more resources.

Another important point to consider is developing access to the Internet. This specialized networkis growing rapidly and provides an incredible amount of resources for a user. The Internet is anarea to share ideas in a GIS forum, download data for use in the system, get technical support for aproblem, get the latest information on a product from a vendors home page or develop one of yourown. The amount of information is overwhelming and too diverse to list in this guide. The point isthat you should seriously be considering getting a connection to the Internet. When consideringyour network, factor this into the equation.

Benchmarking a System

Benchmarking a GIS can be a very involved process. The level of effort needed for the benchmarkshould be proportional to the size and complexity of the overall system being developed. Abenchmark is the process of testing various combination of hardware and software and evaluatingtheir functionality and performance. The benchmark is usually part of an RFP process and is onlydone with a limited number of selected vendors (i.e.: those that have been shortlisted). Eachcombination is tested under similar conditions using a predefined data set that is indicative of yourdatabase. This data set should be used with all of the hardware / software configurations selectedfor evaluation. When completed, an organization will have results that can used to objectivelyevaluate the systems.

Setting It Up

When putting a benchmark together there is strength in numbers. Get a committee together. Acommittee will take the burden off of one person and give the process more objectivity. Haverepresentation from all the interested departments and agencies within the organization. A workinggroup of about 8-10 committee members is reasonable.

The committee will develop the criteria that will be used to evaluate the systems. Use the NeedsAssessment documentation as a reference for this. These criteria will form the basis of thebenchmark. Develop a series of tasks that each vendor will need to complete during thebenchmark. The tasks should be measurable (i.e.: time, ease of use, can the function be done).Also prepare a form that each of the committee members will use to rate the tasks performed in thebenchmark.

In your benchmark you will not only be to rating various aspects of the system, you are also goingto be rating the vendor. Be sure to include some measurement for teamwork, communication, andtechnical skills of the vendor. It might be useful to work with a consultant that has experience


setting up benchmarks or to get advice (and examples of documentation) from another localgovernment who has recently completed a benchmark.

Well in advance of the scheduled benchmarks, send out information that outlines the tasks thevendor will need to perform and any rules they will need to follow (how much time for set up, timegiven to perform various tasks, how many people can be present for the benchmark, etc.).

Vendor Support

The vendor you select will become an extended team member for your GIS. There needs to be agood “fit”. The vendor will be a good source of support and information. All vendors providesome type of technical support. Ask current users how it has worked for them. If there have beenproblems in the past, do existing users see improvement? The GIS industry has been growing veryfast over the last few years, there are bound to be some growing pains. What you should belooking for is a vendor who listens to what you need and makes improvements based on userinput.


Attachment A - User Groups

New York State

Western New York ARC/INFO Users Group (WNYARC)Buffalo area:

Contact: Graham HayesGIS Resource Group, Inc.716-655-5540

GIS/SIGRochester Area:

Contact: Scott Sherwood

Multi-County GIS CooperativeStatewide:

Tri-County GIS Users GroupSouthern Tier:

Contact: Jennifer Fais

GISMONew York City:

Contact: Jack Eichenbaum

Capital Region ARC/INFO User Group (CAPARC)Albany Area:

URISA New York State ChapterContact - Lee Harrington, ProfessorSUNY College of Environmental Science and ForestrySyracusePhone: 315-470-6670Fax: 315-470-6535

Long Island GIS (LIGIS)Contact: Joseph P. Jones

Survey of Available Data 3

National

American Congress on Surveying and Mapping (ACSM)5410 Grosvenor LaneBethesda, MD, 20814Phone: 301-493-0200Fax: 301-493-8245

American Society for Photogrammetry and Remote Sensing(ASPRS) & (GIS/LIS)

5410 Grosvenor LaneBethesda, MD, 20814Phone: 301-493-0290Fax: 301-493-0208

Association for American Geographers (AAG)1710 Sixteenth St. N.W.Washington D.C., 20009-3198Phone: 202-234-1450Fax: 202-234-2744

Automated Mapping/Facility Management International(AM/FM International)

14456 East Evans Ave.Aurora, CO, 80014Phone: 303-337-0513Fax: 303-337-1001

Canadian Association of Geographers (CAG)Burnside Hall, McGill UniversityRue Sherbrooke St. WMontreal, Quebec H3A 2K6Phone: 514-398-4946Fax: 514-398-7437

Canadian Institute of Geomatics (CIG)206-1750 rue Courtwood CrescentOttawa, Ontario, K2C 2B5Phone: 613-224-9851Fax: 613-224-9577

Urban And Regional Information Systems Association (URISA)900 Second St. N.E., Suite 304Washington, D.C. 20002Phone: 202-289-1685Fax: 202-842-1850


GIS DEVELOPMENT GUIDE: DATABASE PLANNING ANDDESIGN

1 1 INTRODUCTION

The primary purpose of this phase of the GIS development process is to specify "how" the GISwill perform the required applications. Database planning and design involves defining howgraphics will be symbolized (i.e., color, weight, size, symbols, etc.), how graphics files will bestructured, how nongraphic attribute files will be structured, how file directories will be organized,how files will be named, how the project area will be subdivided geographically, how GISproducts will be presented (e.g., map sheet layouts, report formats, etc.)., and what managementand security restrictions will be imposed on file access. This is done by completing the followingactivities:

• Select a source (document, map, digital file, etc) for each entity and attribute included inthe E-R diagram

• Set-up the actual database design (logical/physical design)• Define the procedures for converting data from source media to the database• Define procedures for managing and maintaining the database

The database planning and design activity is conducted concurrently with the pilot study and/orbenchmark activities. Clearly, actual procedures and the physical database design cannot becompleted before specific GIS hardware and software has been selected while at the same time GIShardware and software selection cannot be finalized until the selected GIS can be shown toadequately perform the required functions on the data. Thus, these two activities (design andtesting) need to be conducted concurrently and iteratively.

In many cases, neither database design matters nor hardware and software selection areunconstrained activities.. First, the overall environment within which the GIS will exist must beevaluated. If there exist "legacy" systems (either data, hardware or software) with which the newGIS must be compatible, then design choices may be limited. Both GIS hardware and softwareconfigurations and database organizations that are not compatible with the existing conditionsshould be eliminated from further consideration. Secondly, other constraints from anorganizational perspective must be evaluated. It may, for example, be preferable to select a specificGIS or database structure because other agencies with whom data will be shared have adopted aparticular systems. Finally, assuming that the intended GIS (whether it will be large or small) willbe part of a corporate or shared database, the respective roles of each participant need to beevaluated. Clearly, greater flexibility of choice will exist for major players in a shared database(e.g., county, city, or regional unit of government) than for smaller players (town, village, orspecial purpose GIS applications). This does not mean that the latter must always go with themajority, but simply that the shared GIS environment must be realistically evaluated. In fact, oneway for the smaller participants in a shared GIS to ensure their needs are considered, is to fullydocument their needs and resources using procedures recommended in these guidelines.

Finally, with the completion of both the database planning and design and the pilotstudy/benchmark activities, sufficient detailed data volume estimates and GIS performanceinformation will be known to calculate reliable cost estimates and prepare production schedules.This becomes the final feasibility check before major resources are committed to data conversionand GIS acquisition.


What is already known about the GIS requirement

Prior phases of the GIS development process should have produced the following informationwhich is needed at this time:

• A complete list of data, properly defined and checked for validity and consistency (fromthe master data list, E-R data model and metadata entries).

• A list of potential data sources (maps, aerial photos, tabular files, digital files, etc. )cataloged and evaluated for accuracy and completeness (from the available data survey).This inventory would also include all legacy data files, either within the agency orelsewhere, which must be maintained as part of the overall shared database.

• The list of functional capabilities required of the GIS (from needs assessment).

22 SELECTING SOURCES FOR THE GIS DATABASE

This activity involves matching each entity and its attributes to a source (map, document, photo,digital file). The information available for this task is as follows:

• List of entities and attributes from the conceptual design phase

Master Data ListEntity Attributes Spatial

Object--------------------------------------------------------------------------------------------------------------------Street_segment name, address_range LineStreet_intersection street_names LineParcel section_block_lot#, Polygon owner_name, owner_address, sites_address, area, depth, front_footage, assessed_value, last_sale_date, last_sale_price, size (owner_name, owner_address, assessed_value as of previous January 1st))Building building_ID, date_built, Footprint building_material, building_assessed_valueOccupancy occupant_name, occupant_address, None occupancy_type_codeStreet_segment name, type, width, Polygon length, pavement_typeStreet_intersection length, width Polygon traffic_flow_conditions, intersecting_streetsWater_main type, size, material, installation_date LineValve type, installation_date NodeHydrant type, installation_date, Node pressure, last_pressure_test_dateService name, address, type, invalid_indicator NoneSoil soil_code, area

PolygonWetland wetland_code, area PolygonFloodplain flood_code, area PolygonTraffic_zone zone_ID#, area PolygonCensus_tract tract#, population Polygon


Water_District name, ID_number PolygonZoning zoning_code, area Polygon

• The list of surveyed data sources from the Available Data Survey and theirrecorded characteristics in the metadata tables Source Documents, EntitiesContained in Source, and Attributes by Entity.

Source Documents


Source ID #: 1

Source Organization: Town of Amherst

Type of Document: Map

Number of Sheets (map, photo, etc): 200

Source Material: Mylar

Projection Name: UTM

Coordinate System: State Plane

Date Created: 5-Oct-91

Last Updated: 8-Nov-95

Control Accuracy Map: National Map Accuracy Standard

Scale: Variable; 1" = 50 ft To 1" = 200 ft

Availability: Current


Review Date: 19-Dec-95

Spatial Extent: Town of Amherst

File Format: N/A

Comments:


Entities Contained In Source

Source ID #: 1

Entity Name: Parcel

Spatial Entity: Polygon

Estimate Volume Spatial Entity: 126 per map sheet

Symbol: None

Accuracy Description Spatial Entity: National Map Accuracy Standard


Review Date: 02-Jan-94

Scrub Needed: Yes

Comments:

Attributes By Entity

Source ID #: 1

Entity Name: Parcel

Attribute Name: SBL Number


Code Set Name: N/A

Accuracy Description Attribute: N/A

Reviewed By: John Henry

Review Date: 08-Feb-93

Comments:

If there is a choice between sources, that is, two or more sources are available for a particular entityattribute, then criteria for deciding between them will be needed. In general, these criteria will be:

• Accuracy of resulting data• Cost of conversion from source to database• Availability of the source for conversion• Availability of a continuing flow of data for database maintenance.


Occasionally, alternative sources may result in different representations in the database, such as avector representation versus a scanned image. In this situation, the ability of each representation tosatisfy the requirements of the GIS applications will need to be evaluated.

Once a source has been selected, the metadata tables that record source data information need to becompleted as appropriate. These are:

• Data Object Information• Attribute Information• Spatial Object Information• Source Document Information

To complete the accuracy information, the accuracy expected from the conversion process willneed to be determined. This accuracy target will also be used later in the database constructionphase by the quality control procedures. The metadata tables that need to be completed at this timeare shown below:

Data Object Information

Data Object Name Parcel

Type: Simple

Data Object Description: Land ownership parcel

Spatial Object Type: Polygon

Comments:

Attribute Information

Data Object Name: Parcel

Data Attribute Name: SBL Number


Attribute Filename: Parcel.PAT

Codeset Name/Description: N/A

Measurement Units: N/A

Accuracy Description: N/A

Comments:

Spatial Object Information




Place Name: Amherst

Projection Name/Description: UTM

HCS Name: State Plane Coordinate System

HCS Datum: NAD83

HCS X-offset: 1000000

HCS Y-offset: 800000

HCS Xmin: 25

HCS Xmax: 83

HCS Ymin: 42

HCS Ymax: 98

HCS Units: Feet

HCS Accuracy Description: National Map Accuracy Standard

VCS Name:

VCS Datum:

VCS Zmin: 0

VCS Zmax: 0

VCS Units:

VCS Accuracy Description:

Comments:

Source Document Information





Type: Map

Scale: Variable: 1" = 50 feet To 1" = 200 feet

Date Document Created: 17-Nov-89

Date Last Updated: 05-Oct-94

Date Digitized/Scanned: 24-Apr-95

Digitizing/Scanning Method Description: Manual digitized with Wild B8

Accuracy Description: 90% of all tested points within 2 feet

Comments:

For some of the above tables, information will be available for only some of the entries. Theremaining entries will be completed later as the database is implemented. The examples shown arefrom the metadata portion of the GIS Design software package that accompanies these guidelines.This package is a Microsoft Access™ program that runs "stand-alone" (you do not need a copy ofMicrosoft Access™) on a regular PC. Where the same information is needed for multiple tables,this information is only entered once. The information is then automatically transferred to the othertables where it is needed.

3 3 THE LOGICAL/PHYSICAL DESIGN OF THE GIS DATABASE

This activity involves converting the conceptual design to the logical/physical design of the GISdatabase (hereafter referred to as the physical design). The GIS software to be used dictates mostof the physical database design. The structure and format of the data in a GIS, like ARC/INFO™,Intergraph™, MapInfo™, System 9™, etc. have already been determined by each vendorrespectively. If one separates the conceptual entity and its attributes from the corresponding spatialentity and its geometric representation, it can be seen that the physical database design for thespatial entity has been completely defined by the vendor and the GIS designer does not need to doanything more for this part of the data. The attributes of the entities may, however, be held in arelational database management system linked to the GIS. If this is the case, the GIS analyst needsto design the relational tables for the attribute information. Figure 1 illustrates the split between theentity's attributes and the spatial information. This example is based on the ARC/INFO™ GIS anda relational database system.


Entity

KeyAttributes

INFO Coverage Name

SpatialObject Object

Key

Attributes

AttributesAttributes

RDBMS Tables

PAT AAT TIC BND ARC ETC.

KeyAttributes

Figure 1 - GIS Representation of Object and Associated Spatial Object

The translation from the entity representation in the E-R diagram to the physical design of thedatabase for a single entity is shown in Figure 2:

POLYGON G T

PARCEL

COINCIDENTAREA

COINCIDENTAREA

ARC AAT TIC BND ETC. PAT

AreaPerimeterPoly ID #Sub_lot_bl#

Parcel

ParcelINFO Sub_bl_lot#Owner_nameOwner_addSitus_addDepthFront_footageAssessed_valueLast_sale_dateLast_sale_price

Previous Values

Sub_bl_lot#YearOwner_nameOwner_addressAssessed_value

Oracle Tables

Attribute List of Entity "Parcel"

Parcel [subdivision_block_lot#,owner_name, owner_addresssitus_address, area, depth,front_footage, assessed_value,last_sale_date, last_sale_price(owner_name, owner_address,assessed_value as of Jan. 1 forlast two years)]

ARC/INFO Spatial Database Structure

Figure 2 - Example of Mapping of E-R Entity and Attribute List intoARC/INFO™ & ORACLE™ Logical Database


Again, this example is based on ARC/INFO™ and the Oracle relational database system and showshow one entity from the E-R diagram would be represented in a single layer (coverage inARC/INFO™ terms) and two Oracle tables. It will not always be the case where one entity fromthe E-R diagram translates into a single layer. More complex representations will be needed.Generally this will involve two or more entities forming a single layer with, possibly, severalrelational database tables. For example, Figure 3 from the conceptual design guideline shows, inpart, the following entities:

WATER MAINLINK

VALVE

HYDRANT

Figure 3 - E-R Representation of Elements of a Water Distribution System

WATER SYSTEMINFO

ETC ARC TIC BND NAT AAT

WATER MAIN ID #

VALVE ID #

HYDRANT ID #

WATER MAIN

WATER MAIN ID #

VALVE

VALVE ID #

HYDRANT

HYDRANT ID #

ORACLE TABLES

Figure 4 - Physical Design of Several Entities in a Single Layer and ThreeRelational Tables


In figure 4, the water main segments, the valves and the fire hydrants have been placed together inone layer as line segments, and two sets of nodes. However, each entity has its own relationaltable to record its respective attributes (see Table 1, page 2). The relationship is maintained byunique keys for each instance of each entity.

Every entity shown on the E-R diagram must be translated to either a GIS layer, a relationaltable(s), or both, as indicated by the information to be included. In addition, every relationship ofthe type "relationship represented in database" (single line hexagon on the E-R diagram) must beimplemented through the primary and secondary keys in the tables for the entities represented.

PARCEL

POLYGON G T POLYGON G

BUILDINGCONTAINS

LAYER PARCEL ID # BUILDING ID #PARCEL ID #

LAYER

PARCEL TABLE BUILDING TABLE

Figure 5 - Standard Database Relationship with Primary and Secondary Keys

As shown in Figure 5, the entity "parcel" may "contain" the entity "building." The table foreach entity would have its own primary key (ID#), however, the table for building must alsohave a secondary key (parcel ID#) to maintain the relationship in the database.

The completed physical database design must account for all entities and their attributes, the spatialobject with topology and coordinates as needed, and all relationships to be contained in thedatabase. The remaining items on the E-R diagram, the two types of spatial relationships, must beaccounted for in the list of functional capabilities, that is, the implied spatial operations must bepossible in the chosen GIS software

4 4 PROCEDURES FOR BUILDING THE GIS DATABASE

Developing a GIS database is frequently thought of as simply replicating a map in a computer. Ascan be inferred by the nature and detail of the activities recommended up to this point in theseguidelines, building a GIS database involves much more than "replicating a map." Whilesubstantial portions of the GIS database will come from map source documents, many othersources may also be used, such as aerial photos, tabular files, other digital data, etc. Also, the"map" representation is only part of the GIS database. In addition to the map representation and


relational tables, a GIS can hold scanned images (drawings, plans, photos), references to otherobjects, names and places, and derived views from the data. The collection of data from diversesources and its organization into a useful database requires development of procedures to cover thefollowing major activities:

• Getting the Data which may include acquiring existing data from both internal andexternal sources, evaluating and checking the source materials for completeness andquality, and/or creating new data by planning and conducting aerial or field surveys.Contemporary GIS projects attempt to rely on existing, rather than new, data due to thehigh cost of original data collection. However, existing data (maps and other forms)were usually created for some other purpose and thus have constraints for use in a GIS.This places much greater importance on evaluating and checking the suitability ofsource data for use in a GIS.

• Fixing any problems in the data source, often focused only on map sourcedocuments, this activity has been called "map scrubbing." Depending on thetechnology to be used to convert the map graphic image into its digital form, the sourcedocuments will have to meet certain standards. Some conversion processes require themap to be almost perfect which other processes attempt to automate all needed "fixes"to the map. What is required here is for the GIS analyst to specify, in detail, aprocedure capable of converting the map documents into an acceptable digital filewhile accounting for all known problems in the map documents. Thisprocedure should be tested in the pilot project and modified as needed.

• Converting to digital data, the physical process of digitizing or scanning toproduce digital files in the required format. The major decision here is whether or notto use an outside data conversion contractor or to do the conversion within theorganization. In either case, specifications describing the nature of the digital filesshould be prepared. In addition to including the physical database design,specifications should describe the following:

- Accuracy requirements (completeness required, positional accuracy for spatialobjects, allowable classification error rates for attributes).

- Quality control procedures that will be conducted to measure accuracy.- Partitioning of the area covered by the GIS into working units (map sheets) and

how these will be organized in the resulting database (including edge matchingrequirements).

- Document and digital file flow control, including logging procedures, namingconventions, and version control.

• Change control, most map series are not static but are updated on a periodic basis.Once a portion of the map has been sent to digitizing (or whatever process is used), aprocedure must be in place to capture any updates to the map and enter these into thedigital files.

• Building the GIS Database, once digitizing has been completed, the sponsoringorganization has a set of digital files, not an organized database (illustrated in Figure 5).The system integration process (a subsequent guideline document) must take all thedigital files and set-up the ultimate GIS database in a form that will be efficient for theusers. The several considerations required for this process are covered under GIS DataDatabase Construction, GIS System Integration and GIS maintenance and use.


AIdentify

Database Requirements

IdentifyData to beCreated

IdentifyAppropriate

Data Sources

DevelopConceptualDatabase

Design

DetermineConversion

Strategy

DevelopPhysicalDatabase

Design

ProcureConversion

Services

IdentifyAccuracy

Requirements

ADevelop DataConversionWork Plan

CommenceSource

Preparationand Scrub

CommenceOther

In-HouseActivities

FinalizeAcceptanceCriteria and

QC Plan

EditDelivered

Data

CommenceDatabase

Maintenance

DevelopDatabase

MaintenanceProcedures

Figure 6 - Guide to Data Conversion/Database Creation - GIS Data ConversionHandbook

5 5 PROCEDURES FOR MANAGING AND MAINTAINING THE DATABASE

Because the physical world is constantly changing, the GIS database must be updated to reflectthese changes. Once again, the credibility of the GIS database is at stake if the data is not current.

Usually, the effort required to maintain the database is as much as, or more than that required tocreate it. This ongoing maintenance work is usually assigned to in-house personnel as opposed toa contractor. The entire process should be planned well in advance. Once again, the equipmentand personnel must be ready to take over the maintenance of the database when the dataconversion effort and database building processes are complete.

Database maintenance requires two supporting efforts: ongoing user training and user support.Ongoing user training is needed to replace departing users with newly trained personnel. Thiswill enable the data maintenance to be carried out on a continuous and timely basis. It is alsoimportant to offer advanced training to existing users to provide them with the opportunity toimprove their skills and to make better use of the system.

GIS is a complicated technology, making operating problems inevitable. User support will helpusers solve these problems quickly. It will also customize the GIS software to enable them toexecute processing tasks more quickly and more efficiently. User support is usually provided byin-house or contract programmers. It requires a knowledge of the operating system and macroprogramming language as well as troubleshooting common command and file problems.


6 6 GIS DATA SHARING COOPERATIVES

The establishment of data sharing cooperatives within the public sector is a cost-effective means ofdatabase development and maintenance which is encouraged. Cooperative-multiparticipantdatabase projects allow for data exchange, and the opportunity to create new means fordeveloping, maintaining, and accessing information. The sharing of data in the public sector,especially between government agencies and offices which are funded by the same financialresources, should be expected. It does not make fiscal sense for public funds to be utilized in thedevelopment of two GIS databases of the same geographic area for two different agencies.Benefits of data sharing thus would include: the development of a much larger database, for farless cost; the development of more efficient interaction between public agencies; and through theutilization of a single, seamless database the availability of more accurate information, since allagencies would share the same, up-to-date information. Following pages represents a matrixwhich indicates in general opportunities for data sharing between municipal operatingunits/functions.

The goal of a data sharing strategy is to maximize the utility of data while minimizing the cost tothe organization. It is important that all parties involved have clear and realistic expectations aswell as common objectives to make the data sharing work. Under any circumstance, however,database management and maintenance will require us to redefine our relationships with those weroutinely exchange data with, whether they are within an organization or part of a multiparticipanteffort including outside agencies. Work flow and information flow must be reviewed andchanged if necessary. Procedures and practices for the timely exchange and updating of data mustbe put in place and data quality standards adhered to, whether it be hard copy data which must beconverted for inclusion or digital files which might be available for importing to our system.Systematic collection and integration of new and/or update data must be employed in order tosafeguard the initial investment, maintain the integrity of the database and assure, systemreliability to meet function needs.


GIS DEVELOPMENT GUIDE: DATABASE CONSTRUCTION

11 INTRODUCTION

Scope Of Database Construction

A database construction process is divided into two major activities

• creation of digital files from maps, air photos, tables and other source documents;• organization of the digital files into a GIS database.

This guideline document describes the first process, digital conversion, and the subsequentguideline entitled "GIS System Integration" deals with the organization of the digital files into adatabase.

Figures 1 and 2 are two versions of the digital data conversion process (Burrough, 1986; andMontgomery and Schuch). Only the second half of figure 2 describes the actual digital conversionprocess, the first half identifies previous planning activities. In both figures, the end product(s) aredigital data files which, if passed through quality control, are suitable for inclusion in the GISdatabase.

Steps in creating a topologically correct vector polygon database

FIELD DATA

NON-SPATIALATTRIBUTES

SPATIALDATA

INPUT TO TEXT FILE

MANUAL DIGITIZING

DIGITIZE SCAN AND VECTORIZE

SCANNING

linked by unique

indentifiers

VISUAL CHECK

CLEAN UP LINES AND JUNCTIONS

WEED OUT EXCESSCOORDINATES

CORRECT FORSCALE AND

WARPING

ADD UNIQUEIDENTIFIERSMANUALLY

CONSTRUCTPOLYGONS

LINK SPATIALTO NON-SPATIAL DATA

TOPOLOGICALLY CORRECTVECTOR DATABASE OFPOLYGONS

Figure 1 - Source: Principles of Geographic Information


Systems for Land Resources Assessment, Burrough, P .A. ,1986

AIdentify



IdentifyAppropriate

Data Sources


Design

DetermineConversion

Strategy


Design

ProcureConversion

Services

IdentifyAccuracy

Requirements


CommenceSource


CommenceOther

In-HouseActivities


QC Plan

EditDelivered

Data

CommenceDatabase

Maintenance

DevelopDatabase


Figure 2 - Guide to Data Conversion. Source: Montgomery and Schuch

22 INFORMATION REQUIRED TO SUPPORT DATA CONVERSION PROCESS

Data Model

GIS technology employs computer software to link tabular databases to map graphics, allowingusers to quickly visualize their data. This can be in the form of generating maps, on-line queries,producing reports, or performing spatial analysis.

To briefly summarize the characteristics of GIS software and the data required for operations, weoffer the following diagram:


GIS Data Model

123

123

Layers ofMap Graphics

Tabular Databases

Graphic / Data links

Figure 3 GIS Data ModelGIS (Spatial) Data Formats

In digital form, GIS data is composed of two types: map graphics (layers) and tabular databases.

• Map graphics represent all of the features (entities) on a map as points, lines, or areas,or pixels.

• Tabular databases contain the attribute information which describe the features(buildings, parcels, poles, transformers, etc.).

GIS data layers are created through the process of digitizing. The digitizing process produces thedigital graphic features (point, line or area) and their geographical location. Tables can be createdfrom most database files and can be loaded into a GIS from spreadsheet or database softwareprograms like Excel™, Access™, FoxPro™, Oracle™, Sybase™, etc. A common key must beestablished between the map graphics and the tabular database records to create a link. This link isusually defined during the “scrubbing” phase (data preparation) and created during data capture(digitizing). For parcel data, the parcel-id or SBL number (section, block and lot) is a goodexample of a common key. The map graphic (point or polygon) is assigned an SBL number as itis digitized. The database records are created with an SBL number and other attributes of theparcel (value, landuse, ownership, etc.).

Raster and Vector Format

GIS allows map or other visual data to be stored in either a raster or vector data structure:

There are two types of raster or scanned image: 1) remotely sensed data from satellites; and 2)scanned drawings or pictures. Satellite imagery partions the earth's surface into a uniform set ofgrid cells called pixels. This type of GIS data is termed raster data. Most remote sensing devicesrecord data from several wave-lengths of the electromagnetic spectrum. These values can beinterpreted to produce a "classified image" to give each pixel a value that represents conditions onthe earth's surface (e.g., land use/land cover, temperature, etc.). The second type of scannedimage is a simple raster image where each pixel can be either black or white (on or off) or can have


a set of values to represent colors. These scanned images can be displayed on computer screens asneeded.

Raster data is produced by scanning a map, drawing or photo. The result is an array of pixels(small, closely packed cells) which are either turned "on" or "off." A simple scanned image, forexample, in TIFF (Tagged Image File format) format, does not have the ability to be utilized forGIS analysis, and is used only for its display value. The "cells" of the digital version of the imagedo not have any actual geographical nature as they represent only the dimensions of the originalanalog version of the image. Raster data in it’s most basic form is purely graphical and has no“intelligence” or associated database records.

Raster GIS Data

Graphics Grid/Raster Value Attribute Table

2

2

2

2

2

2

2

2

2

2

3

3 3

3 3

3 3

3

3

5 55

5555

5

5

5

5

5

3

5 5 5 5

Cell Value Real World Entity2 Lake3 Wooded5 Built-up

Figure 4 - Raster Data (pixels)

Raster data can be enhanced to provide spatial analysis within a GIS. Pixels or cells representmeasurable areas on the earth's surface and are linked to attribute information. These cells areassigned numeric values which correspond to the type of real-world entity which is represented atthat location (e.g., cells containing value "2" may represent a lake, cells of value "3" may representa particular wooded area, etc.).

• Vector data represents map features in graphic elements known as points, lines andpolygons (areas).


12

3

Vector GIS Data

Polygon Attribute Table

Polygon Number Identity Attribute 1 Lake 2 Wooded 3 Built-up

Vector GIS Polygon Layer

Figure 5 - Vector GIS Data

Vector graphics coordinates are represented as single, or a series of, xy-coordinates. Data isnormally collected in this format by tracing map features on the actual source maps or photos witha stylus on a digitizing board. As the stylus passes over the feature, the operator activates theappropriate control for the computer to capture the xy-coordinates. The system stores the xy-coordinates within a file. Vector data can also be collected on-screen (called "heads-up"digitizing), by tracing a scanned image on the computer screen in a similar manner.

33 DATA CONVERSION TECHNOLOGIES AVAILABLE

Manual Digitizing

Manual digitizing involves the use of a digitizing tablet and cursor tool called a “puck,” a plasticdevice holding a coil with a set of locator cross-hairs to select and digitally encode points on a map.A trained operator securely mounts the source map upon the digitizing tablet and, utilizing the crosshairs on the digitizing “puck,” traces the cross hair axis along each linear feature to be captured inthe digital file. The tablet records the movement of the puck and captures the features’ coordinates.The work is time-consuming and labor intensive. Concentration, skill and hand-eye coordinationare crucial in order to maintain the positional accuracy and completeness of the map features.

Traditional data conversion efforts are based on producing a vector data file compiled by manuallydigitizing paper maps. Vector data provides a high degree of GIS functionality by associatingattributes with map features, allowing graphic selections, spatial queries and other analytical usesof the data. Vector data also carries with it the highest costs for conversion. The industry averagefor a complete data conversion project to digitize parcel lines, dimensions and text is between$3.00 - $5.00 per parcel. The price is determined by the complexity and amount of data. To keepcosts down, data can be selectively omitted from conversion (i.e. not all text and annotation will becaptured). The resulting vector data can reproduce a useful, albeit more visually stark version ofthe original map. A bare bones data conversion project can be conducted by digitizing only thelinework from the tax maps. The minimum industry cost for digitizing parcel line work with aunique ID only is between $1.00 to $1.50 per parcel.

Scanning


Scanning converts lines and text on paper maps into a series of picture elements or “pixels.” Thehigher the resolution of the scanned image (more dots per square-inch), the smoother and moreaccurately defined the data will appear. As the dots per inch (DPI) increases, so does the file size.Most tax maps should be captured with a scan resolution of 300-400 DPI. One of the mainadvantages to scanning is that the user sees a digital image that looks identical to their paper maps-- complete with notes, symbology, text style and coffee stains, etc. Scanning can replicate thevisual nature of the original map at a fraction of the cost of digitizing. However this low cost has a"price". The raster image is a dumb graphic -- there is no “intelligence” associated with it, i.e.individual entities cannot be manipulated. Edge-matching and geo-referencing the images(associating the pixels with real world coordinates) improves the utility of the scanned images byproviding a seamless view of the raster data in an image catalog. Scanned images require moredisk space than an equivalent vector dataset, but the trade-off is that the raster scanning conversionprocess is faster and costs less than vector conversion.

Raster to Vector Conversion

Scanned data, in raster format, can be "vectorized” (converted into vector data) in many high-endGIS software packages or through a stand-alone data conversion package. Vectorizing simplyinvolves running a scanned image through a conversion program. In the vectorization process,features which are represented as pixels are converted into a series of X,Y points and/or linearfeatures with nodes and vertices. Once converted within a GIS environment, the data is in thesame format created using a digitizing tablet and cursor. Many vectorized datasets requiresignificant editing after conversion.

Hybrid Solution

Since both vector and raster datasets have decided advantages and disadvantages, a hybrid solutioncapitalizes on the best of both worlds. Overlaying vector format data with a geo-referencedbackdrop image provides a powerful graphic display tool. The combined display solution couldshow the vector map features and their attributes (also available for GIS query), and an exactreplica of the scanned source material which may be a tax map or aerial photography. If needed,individual parcels, pavement edges, city blocks or entire maps can be vectorized from the geo-referenced scanned images. This process is called incremental conversion. It allows the county toconvert scanned raster data to vector formatted data on an as-needed basis. There are a plethora ofraster to vector conversion routines on the market, but it is important that the conversion take placein the same map coordinate system and data format as your existing data. The key advantage to thehybrid approach is this: even after full vectorization, the scanned images continue to provide ahigher quality graphic image as a visual backdrop behind the vector data.

Entry of Attribute Data

Additional attribute data can be added to the database by joining a table which contains the newattributes to an existing table already in the GIS. To join these tables together a common field mustbe present. Most GIS software can then use the resulting table to display the new attributes linkedto the entities. There are various sources for building an attribute database for a GIS. From CD-ROM telephone and business market listings with addresses, to data which is maintained in variousgovernment databases in “dbase” or various other database formats.


Acquisition of External Digital Data

The availability of existing digital data will have an effect upon the design of the database.Integrating existing databases with the primary GIS will require the establishment of common datakeys and other unique identifiers. Issues of data location, data format, record match rates, and theoverall value of integrating the external data should all be considered before deciding to purchase oracquire existing datasets.

GIS Hardware And Software Used in Digital Data Conversion

Most contemporary GIS software packages are structured to operate on computer workstations toaccomplish digitizing and editing tasks.Four basic types of workstations can be identified:

• A digitizing station, a workstation which is connected to a precision digitizing tablet,which utilizes a high-resolution display terminal, and which also has all of the analysisfunctions necessary for querying, displaying and editing data

• An editing workstation, which is used for conducting most of the QA/QC functions ofthe conversion process, having all the functionality of the digitizing station except forthe ability to digitize data via a digitizing tablet

• Graphic data review/Tabular data input workstations are used for displaying andreviewing graphic data, and for the entering of tabular attribute data associated withthese features

• X Terminals are the fourth type of workstation and these allow for graphic display andinput of data utilizing the X Window System communications protocol.

With the increasing power of today’s personal computers, many GIS analysis packages are beingdesigned for PC’s. As GIS data files are very large, PC-based GIS packages usually require a PCwith minimum requirements including a 486 processor and 16 megabytes of RAM. Hard-drivedisk space depends upon how large the datasets are which are being used. A safe bottom-line forhard-drive space with a PC is 500 megabytes. For most data conversion projects, much morehard-drive space will be needed in order to store data as they are converted. Tape storage hardwareis also necessary in order to efficiently backup the many megabytes of files created in theconversion process. Just to provide an idea of the storage requirements necessary for basicscanning conversion, the file-size of one tax map alone, in (Tagged Image File Format or TIFF)image format, scanned at a 500 dots per inch (dpi) resolution, can range anywhere from 1-3megabytes alone.

Digitizing hardware requirements vary according to the conversion approach which is applied. Forvector conversion, a digitizing tablet will be necessary in usually a manual digitizing process.Another piece of digitizing hardware, a scanner, is used to create raster images. Automaticdigitization, through the use of a scanner is a very popular approach for capturing data. Raster datacan subsequently be transformed into vector data in most turn-key GIS packages, through the useof raster-to-vector conversion algorithms.

After the conversion of map data into digital form, hardware will be needed for outputting digitaldata in hardcopy format. When handling a data conversion project, a necessary piece of output


hardware is a pen or raster plotter. GIS software allows for the creation of plots at any viewscale.The plotter, with its ability to draw on a variety of materials (including paper, mylar and vellum),allows for the creation of quality map plots. Most plotters usually have a minimum width of threefeet. Vector and raster plotters are both available on the market. Vector, pen plotters utilizevarious pens for the drawing of linear features on drawing media. Pen plotters can handle mostplotting jobs, but they do not produce good results in area shading such as in the production ofcholorpleth maps. Raster plotters, on the other hand, are excellent in producing shading results.Raster plotters usually cost more than vector plotters, but are substantially more versatile and havebetter capabilities.

Other output devices for the creation of hardcopies of GIS data include: screen copy devices, usedfor copying screen contents onto paper without having to produce a plot file; computer FAX(facsimilie) transmissions, often used in communications between conversion contractors andclients, produce small letter-size plots, and the fax transmission files (as raster images) can besaved and viewed later; printers are used to output tabular data which is derived from the GIS, andif configured correctly, can produce small letter-size plots.

Pilot Project/Benchmark Test Results

The pilot project is a very important activity that precedes the data conversion project. The pilotproject allows you, the GIS software developer, and the data conversion contractor the ability totest and review the numerous steps involved in creating the database. Defining the pilot study areainvolves selection of a small geographic area which will allow for a high degree of beingsuccessful, that is, that it will be completed in a relatively short period of time and will allow forthe testing of all project elements which are necessary (conversion procedures, applications,database design). Test results which are obtained from the pilot project usually includeassessments of: database content, conversion procedures, suitability of sources, database design,efficiency of prepared applications on datasets, the accuracy of final data, and cost estimates.

Identified Problems With Source Data

The pilot study involves testing and finding successes and problems in procedures and designs forthe GIS. It involves looking for problems that occur due to lack of, or inadequacy in, source data.It is important to identify problems especially at the source data level since it is usually the easiestand cheapest to correct errors prior to data conversion.

When evaluating the results of a pilot study, problems with digital data accuracy resulting fromsource data flaws, are bound to arise. Usually, the source data used for a project are not in theproper format required for the best possible data result. For example, problems may arise whenthe source data for a certain data layer consists of maps which are at various scales. These variousscale differences can create error when these digitized layers are joined into a single layer. Otherproblems arise when there are not adequate control points found upon map sheets in order toaccurately register coverages while they are being digitized. At times, even adjacent large-scalesource map sheets may have positional discrepancies between them. Such inconsistencies will bereflected in the corresponding digital data. Procedures for dealing with all known source dataproblems need to be specified prior to the start of data conversion.


44 DATA CONVERSION CONTRACTORS

Firms Available And Services Offered

There are different types of firms which can handle GIS data conversion. There are some firmswhich specialize in GIS data conversion, and sub-contract out the services of other firms asneeded. Some other firms which handle data conversion but do not particularly specialize in dataconversion alone include: aerial mapping firms, engineering firms and GIS vendors. Variousfirms will offer standard data conversion services, but based upon their main type of work, mayoffer some unique services. For example, a firm specializing in GIS data conversion may have awide variety of software options which the client company can choose from. Such a firm usuallywill have numerous digitizing workstations and a large staff, and be able to complete the project ina shorter period of time than other firms which do not particularly specialize in GIS dataconversion. If needed, a specialized GIS data conversion company could subcontract servicesfrom another company.

Aerial mapping firms can offer many specialized data conversion services associated withphotogrammetry, which will not be available directly through a general data conversion contractor.Many aerial mapping firms now have considerable expertise with the creation of digital orthophotoimages, rectified and scaled scans of aerial photography, which can be displayed and utilized withvector data. Engineering and surveying firms are well-equipped to deal with most data conversionprojects, and will usually have a major civil engineering/surveying unit within the organization.These firms usually will focus upon certain aspects of GIS systems and approach conversionprojects with stress upon the extent of construction detail, positional accuracy requirements,COGO input, scale requirements and database accuracy issues. At times, GIS software vendorswill handle data conversion projects in order to test their software in benchmark studies and pilotprojects.

The main conversion services which are usually offered include: physical GIS database design andimplementation, deed research, record compilation, scrubbing, digitizing, surveying, programmingand image development and registration.

Approximate Cost of Services

Outsourcing data conversion with data purchase/ownership

CONVERSION METHOD PER-PARCEL COSTManually digitized vector data $1.20 / Parcel(linework alone)

Manually digitized vector data $5.00 / Parcel(linework & annotation)

Vector data developed from the vectorizationof scanned maps (linework & Annotation) $3.00 / Parcel


Raster image data (registered to a coordinate system) $50. / map = $0.55 / Parcel

Outsourcing Data Conversion and Licensing Data

CONVERSION METHOD PER-PARCEL COSTManually digitized Vector Data(Linework and Annotation) $1.50 / Parcel

(No cost estimates are available for Raster Data)

(Note: All of the above cost estimates are based upon average prices offered by various dataconversion vendors)

Making Arrangements For External Data Conversion

There are a number of ways of obtaining the digital conversion of map data. Arrangements areusually made through the development of a Request for Proposal (RFP), and then evaluating theproposals submitted by various conversion contractors. Some of the criteria which are desired inselecting a conversion contractor include: the company’s technical capability, the company’sexperience with data conversion, the company’s range of services, location, personnel experienceand the overall technical plan of operation. Balanced with all of these items is usually theorganization’s budget and the costs associated with the project.

55 DATA CONVERSION PROCESSES

Digital Conversion Of Mapped Data

Digital data conversion of mapped data is a costly and time-consuming effort. The more closelythe digital data reflects the source document, and the more attributes are associated with the mapfeatures, the higher the map utility but also the higher the cost of conversion. Because of the highcost of digitizing all graphic map features, and text/graphic symbology, conversion efforts maycompromise data functionality by limiting the number of features captured in order to keep costsdown. The actual processes involved with digital conversion of mapped data are usually the mostinvolved, and most time-consuming of all. These two traits together explain why data conversionis usually the highest cost of implementing the GIS.

Planning The Data Conversion Process

The data conversion process needs to be planned effectively in order to minimize the chance of dataconversion problems which can greatly disrupt the normal workflow of the organization. It is


necessary to plan all of the physical processes which will be involved in data conversion and todevelop time-estimates for all work. These main processes include:

• Specifications• Source map preparation• Document flow control• Supervision plans• Problem resolution procedures

These procedures allow for the efficient conversion of mapped data. Guidelines for normal datacapture procedures such as scanning and table digitizing should be developed to ensure that all dataare consistently digitized. Particularly when an organization is conducting conversion in-house, asmall amount of time invested in developing error prevention procedures will greatly benefit theorganization by saving time in the correction/editing phase of the conversion. It is easier to preventerrors than to go ahead and try to correct them after the actual digitizing has been conducted.

Data Conversion Specifications: Horizontal And Vertical Control, Projection;Coordinate System, Accuracy Requirements

Any discussion about data conversion should start with the topic of accuracy. We've all heard theexpression, "Garbage In, Garbage Out." Without the ability to meet the proper accuracy standardsestablished early in a GIS conversion project, the resulting GIS may be useless based upon its lackof accuracy. Even still, in reality, when building a GIS and handling data conversion, we arefaced with a variety of source documents which may each carry a different scale, resolution,quality and level of accuracy. Some source map data may be so questionable that it should not beloaded into the GIS. Extracting reliable data later-on from the GIS will depend upon either theconverting of data from reliable source documents, or the development of new data "from scratch."

Map projections affect the way that map features are displayed (as they affect the amount of visualdistortion of the map), and the way map coordinates are distributed. Before any GIS graphic datalayers will be ready for overlay functions, the layers must be referenced to a common geographiccoordinate system. GIS software can display data in any number of projection systems, such asUTM (Universe Transverse Mercator), State Plane Coordinate Systems, and more. For scannedmaps and aerial photos (which are simple non-GIS raster images), to be displayed effectively withvector data, the images need to be registered and rectified to the same coordinate system.

Establishing specific requirements for map accuracy should be done at the beginning of a project.If a certain level of accuracy is desired, it is this level which will have to be developed in futureaspects of the project. Procedures should be standardized in order to ensure the best and mostconsistent results possible.

Source Map Preparation (Pre-Digitizing Edits)

Preparing the analog data that will be converted is an important first step. This needs to be donewhether the data will be scanned or digitized, and whether you are outsourcing the work or


completing it in-house. This pre-processing is also referred to as “scrubbing” the data. The processinvolves coding the source document using unique ID’s and/or using some method to highlight thedata that should be captured from these documents. This makes it clear to the person performingthe scanning or digitizing what they should be picking up. It will also be important later forperforming quality control checks and to make sure that the digital data has a link to the attributedatabase needed for a GIS.

Document Flow Control

Without a clear system for monitoring and planning the flow of map (and attribute data) documentsbetween the normal storage locations of map documents and those parties handling the actual dataconversion, problems will usually arise in tracking the location of maps. When a large number ofmaps are being converted, it is important to maintain a full understanding between both theconversion contractor or in-house conversion staff, and the normal user group of the sourcedocuments about exactly which documents are being handled, and at what time. Source maps aredelivered to the conversion group or contractor as a work packet, usually consisting of amanageable number of maps of a certain geographic region, which is pre-determined within thedata conversion workplan. A scheme for tracking packets of source documents, as well as theresulting digital files is needed. This scheme should be able to track the digital file through thequality control processes.

In addition to tracking the flow of documents and digital files through the entire data conversionprocess, a procedure needs to be established for handling updates to the data that occur during theconversion time period. This change control procedure may be quite similar to the final databasemaintenance plan, however, it must be in place before any of the data conversion processes arestarted. Also, if this procedure will likely be very different from the previous manual mapupdating methods used and may involve substantial restructuring of tasks and responsibilitieswithin the organization.

Supervision Plans (Particularly For Contract Conversion)

When planning the data conversion process, it is important that attention be given to thedevelopment of detailed plans for supervising the data conversion process. Supervisory plansallow the organization to distribute responsibility for the many different facets of the dataconversion project. When data conversion has been contracted out, it is important thatcommunication be maintained between the client company and the contractor. The development ofspecific variations normal administrative tools used for scheduling and budget control can be veryuseful (e.g., CPM/PERT scheduling procedures; GANTT charts, etc.)

Problem Resolution Procedures

In order to ensure the efficient progress of all aspects of the data conversion project, it is importantto develop formal procedures for problem resolution. Editing procedures and data standardsshould be developed for such items as: major and minor positional accuracy problems; inaccuraterubber-sheeting, or map-joining/file-matching problems; attribute coding errors, etc. Otherprocedures for events such as missing source data, handling various scale resolution issues, and


even hardware and software system problems should also be created. Establishing suchprocedures and assigning responsibilities for resolution are extremely important, particularly whenoutside contractors are involved.

Converting The Data

As stated earlier, it is important to follow consistent pre-established procedures in the actualdigitizing of the datasets. Consistently using a tested and approved set of conversion guidelinesand procedures will eliminate any chance of ambiguity in methods. Using established procedureswill allow for the most consistent product possible.

Reviewing Digital Data

The digital data review process involves three issues:

• data file format and format conversion problems• data quality questions• data updating and maintenance

The review process must first be handled before the decision to rely on other digital data sources ismade. Additionally, formal data sharing agreements should be made between the twoorganizations.

Quality Control (Accuracy) Checking Procedures

A quality assurance (QA) program is a crucial aspect of the GIS implementation process. To besuccessful in developing reliable QA methods, individual tasks must be worked out anddocumented in detail. Data acceptance criteria is a very important aspect of the conversionprogram, and can be a complex issue. A full analysis of accuracy and data content needs willfacilitate the creation of documentation which may be utilized by the accuracy assessment team.A combination of automatic and manual data verification procedures is normally found in acomplete QA program. The actual process normally involves validation of the data against thesource material, evaluation of the data’s utility within the database design, and an assessment of thedata with regard to the standards established by the organization handling the conversion project.Automated procedures will normally require customized software in order to perform data checks.Most GIS packages today have their own macro programming languages which allow for thecreation of customized programs. Some automated QA procedures include: checking that allfeatures are represented according to conversion specifications (e.g., placed in the correct layer);features requiring network connectivity are represented with logical relationships, for example, twodifferent diameters of piping or two different gauges of wire must have a connecting devicebetween them which should be represented by a graphic feature with unique attributes;


relationships of connectivity must be maintained between graphic features (Montgomery andSchuch, 143).

Manual quality control procedures normally involve creating and checking edit plots of vector dataagainst source map data. QA requirements which will have to be met include: absolute/relativeaccuracy of map features should be met and all features specified on the source map should beincluded on the edit plot; map annotation should be in required format (e.g., correct symbology,font, color, etc.) and text offsets should be within specified distance and of correct orientation;plots of joined datasets should have adequate edge matching capability (M&S, 145).

Final Correction Responsibilities

Quality control editing of the digitized product is a crucial step in preparing spatial feature data.After initially digitizing a data layer, an edit plot is produced of those digitized features. The editplot is a hard-copy printing of the digitized features. The edit plot is printed at the same scale as thesource data and checked by overlaying the plot with the source map on a light table. This editcheck allows for the determination of errors such as misaligned or missing features. Correctionsmay then be made by adding or deleting and re-digitizing features. When on-screen digitizing,feature placement errors may be corrected by “rubbersheeting” the graphic features to fit the sourcedata. Rubbersheeting is the process of stretching graphic features through the establishment ofgraphic movement “links” with a from-point (where the feature presently is located), and a to-point(where the feature should be placed). GIS graphic manipulation routines then move graphicsaccording to these specified links.

File Matching Procedures (Edge Match, Logical Relationships Within Data, Etc.)

Files which are going to be spatially joined must first have adequate edge-matching alignment oftheir graphic features. This entails a number of basic GIS graphic manipulation procedures: (1)coordinate transformation, which projects the data layer into its appropriate real-world coordinates;(2) rubbersheeting of the graphic features in one data file to accurately coincide with the adjacentgraphic features in another file; (3) spatial joining, the combining of two or more data files intoone seamless file spanning the geographic area of all files.

Coordinate transformation is the process of establishing control points upon the digitized layer anddefining real-world coordinates for those points. A GIS coordinate transformation routine is thenused to transform the coordinates of all features on the data layer based upon those control pointcoordinates. Once transformed, spatially adjacent data layers may then be displayedsimultaneously within their combined geographic extent. A determination may then be made as tothe effectiveness and accuracy of the coordinates assigned to the data layers. If necessary, graphicfeatures found in both data layers may be rubbersheeted to better align features which will need tobe connected. For example, if the endpoint of a graphic feature representing a street centerline isnot reasonably close to its corresponding starting point on the adjacent data layer, one or both ofthese graphic lines will have to be moved so that the graphic feature will connect. An alignmentproblem such as this can signal possible errors in the coordinate transformation and/or the sourcedata. After features are accurately matched, the data files may be combined into a single data file.The combined data file will afterwards require editing and the development of new topologicalrelationships in the new dataset. An example of one post-spatial join editing procedure is the


removal of graphic line-connection points called “nodes” which may interfere with variouselements of the attribute database.

Final Acceptance Criteria

Standards for appropriate quality assurance, and accuracy verification procedures in general,depend greatly upon the data sources, the schematics of the database for which data is beingprepared, and the actual data conversion approaches applied. Acceptance of the joined digital mapfiles depends upon the data’s meeting certain criteria. Criteria usually relate to accuracy, such asthe determination of whether the product meet National Map Accuracy Standards at the appropriatescale. Other criteria may relate to whether attributes are in order, if they have been added. Mostacceptance determinations should be made on whether the feature data is meeting standards ofaccuracy, completeness, topological consistency, and attribute data content.

Building Main Database

One of the final stages involved in developing a GIS database involves putting all the converteddata together. Establishing one uniform database involves entering all attribute and feature datainto a common database with an established workable file/directory structure, sometimes known asa “data library.” As the database is developed and data is ready for use, it can be released to thevarious data users for analysis. Once the database is designed, it then becomes important tomaintain data accuracy and currency. If changes are made within the confines of the data layers,these changes must be defined and updates made to keep the integrity of the database. Subsequentguideline documents deal with data integration and database maintenance.

66 ATTRIBUTE DATA ENTRY

Source Documents

There are a number of source documents which can be utilized as data for the attribute database.Many organizations are able to utilize their existing electronic database files and import this datadirectly into their GIS database. In the case of paper files relating to geographic areas, and attributedata existing on paper maps, this data will have to be manually entered into GIS attribute data filesin the form of tables. Before this information is entered into a database, it must first be reviewedand edited. It is also important to have a procedural plan designed for the entry of this data in orderto coordinate the flow of these source documents.

Pre-Entry Checking And Editing

A review of GIS attribute source documents can oftentimes reveal an unorganized mass of maps,charts, tables, spreadsheets, and various textual documents. The checking and editing of source


documents is handled in the scrubbing phase of the project. Without a specific plan designed forthe entry of these various data elements, it is highly likely that error will be introduced into the GISdatabase. It is crucial that all source documents are readable and properly formattedto allow for the most efficient entry of numerical and textual data. If the database conversion isbeing outsourced, and the contractor is unable to read the source data, the resulting database will beinaccurate, more costly, or both. It is recommended that a formal scrub manual, designedaccording to the database and application requirements, be developed to help facilitate thesupplementing of source data and its entry into the database. Logical consistency is an importantelement for both graphic and attribute elements. Records and attributes which are related to graphicelements within a network system must maintain logical relationships.

Document Flow Control

An organization will typically have a multitude of different document formats which it will need incoding all of its GIS attribute data. It is crucial that tracking mechanisms be implemented inpreparation for the key entry process. Usually duplication of source documents which will be usedin the key entry process will not be feasible. As many source documents to be key entered areused on a regular basis within the organization, it will be important to develop guidelines fortracking these documents if they are needed during the process. Timing and coordination will befactors in planning document usage.

Key Entry Process

As stated earlier, some organizations will be able to enter much tabular data into the databasesimply by way of importing existing tables or files into the GIS, or relating tables which exist intheir external DBMS. Normally, it will be necessary to enter attribute data into the system utilizinga keyboard. Many organizations choose to use lists when entering data from the keyboard. It ismuch more efficient during conversion to enter a 2 or 3-digit code which has a reference listassociated with it. Typing in a full description of the graphic into the text field takes longer, andincreases the chance of typographical error.

Digital File Flow Control

Numerous files will result from the key entry process. These files will need to be given propernames and directory locations in order to track and prepare the data logically for use within theGIS.

Quality Control Procedures

Most databases allow the user to specify the type of field for each data element, whether it isnumeric, alphanumeric date, etc; whether it has decimal places, and so on. This feature can helpprevent mistakes as the system will not allow entries other than those specified in advance.

There are a number of automated and manual procedures which can be performed to check thequality of attribute data. Some customized programs may be required for the testing of some


quality control criteria. Some attribute value validity checks which may be performed include:verifying that each record represents a graphic feature in the database, verifying that each featurehas a tabular record with attributes associated with it, determining if all attribute records are correct,and determining that all attributes calculated from certain applications must be correct based uponthe input values and the corresponding formulas. The translation of obsolete record symbologyinto a GIS usable format, according to conversion specifications, is one procedure which will haveto be conducted manually (Montgomery and Schuch, 145).

The responsibility for checking and maintaining automated quality control procedures can be placedin the hands of the staff responsible for actual data conversion. When outsourcing dataconversion, one of the most time-consuming aspects of the project is the evaluation of converteddata once it has been received from the vendor. Usually, automated routines are developed whichcan be utilized in the evaluation of the datasets, and in determining if the data fulfills all of therequirements and standards stated in the contract. This process can be simplified by the clientcompany delivering automated quality control checking routines to the data conversion vendor.The vendor is then able to run these routines, evaluate and edit the data so that it will meetrequirements before it is even shipped to the client. Such a procedure saves valuable time andexpenses which would otherwise have been spent on quality control evaluation, shipping andbusiness communication.

Change Control

Final editing procedures and data acceptance are based upon whether major revisions in the datawill need to be performed. After data verification and quality assurance checks, it may benecessary to again re-evaluate database design, technical specifications of the data, and conversionprocedures overall. Ideally, the planning and design of the database will be sufficientlycomprehensive and correct such that the logical/physical database design will not have to bemodified. However, it is rare that a data conversion project will be able to push through tocompletion without some changes being necessary. Many conversion projects develop procedureswhich are used to identify, evaluate and then to approve or disapprove the final products. A formshould be developed which is used to list desired changes which have been identified. The listingof desired changes is then evaluated in terms of both the volume of the data which has yet to beedited, and the amount of data which has already been converted. The conversion vendor willusually develop documentation which describes the estimated cost/savings which will be associatedwith the changes and final edits. Most organizations now accept the fact that changes will be anormal part of data conversion and change requests are usually expected. The challenge then liesin the methods by which change mechanisms are developed and agreed upon between client andvendor.

Final Acceptance Criteria

Acceptance criteria are the measures of data quality which are used to determine if the dataconversion work has been performed according to requirements specified. In the case ofoutsourcing of conversion, these criteria will determine if the data has been prepared according tothe contract specifications. If the data does not meet these specifications, the conversion contractorwill be required to perform any necessary editing upon the data to reach acceptable standards.Acceptance criteria and standards may vary between organizations.


File Matching And Linking

In most GIS packages which utilize relational database technology, the file matching and linking isa fairly simple process. Most GIS packages contain straight-forward procedures for joining andrelating attribute files, which normally entails the selection of the unique identifying key betweenthe graphic feature attribute table and any other data attribute tables. Once the identifier-link hasbeen specified, the GIS software automatically establishes the relationship between the tables, andmaintains the relationship between them.

77 EXTERNAL DIGITAL DATA

Sources Of Digital Data

Digital spatial and attribute data can be found from a variety of sources. Various companies todayproduce “canned” digital spatial datasets which are ready for use within a GIS environment.Utilizing an existing database is a good way to supplement data in the conversion process and isone of the best ways to save money on the cost of producing a database. Most federal, state, andlocal government agencies have data which is available to the public for minimal cost.

Two of the largest spatial databases which are national in coverage include the US. GeologicalSurvey’s DLG (Digital Line Graph) database, and the U.S. Census Bureau’s TIGER(Topologically Integrated Geographic Encoding and Referencing) database. Both systems containvector data with point, line and area cartographic map features, and also have attribute dataassociated with these features. The TIGER database is particularly useful in that its attribute dataalso contains valuable Bureau of the Census demographic data which is associated with blockgroups and census tracts. This data is used today in a variety of analysis applications. Manycompanies have refined various government datasets, including TIGER, and these datasets offervarious enhancements in their attribute characteristics, which increases the utility of the data.Unfortunately, problems associated with the positional accuracy of these datasets usually remainand are much more difficult to resolve.

Satellite and digital orthophoto imagery, raster GIS datasets, and tabular datasets are also availablefrom various data producing companies and government agencies.

Transfer Specifications

Many government agencies produce spatial data which is in its own unique format. Many full-feature GIS packages have the ability to import government spatial datasets into data layers whichare usable within their own environment. Some agencies or companies may produce their data in


the most common data formats for government data in the transfer of their data (e.g. TIGER orDLG format). Such policies allow for easy transfer to various systems.

Quality Control Checks

Quality control checks on external datasets will be necessary. Many government datasets, althoughextensive in their geographic coverage and in the utility of the associated data, do not always havethe most accurate or complete data, particularly in terms of positional accuracy. It is alwaysadvisable to be skeptical of a dataset’s accuracy statement and compliance with standards and tofully test and evaluate the data before purchasing it or incorporating it into the database. Variousautomated and manual quality control procedures, discussed for both assessing cartographicfeature and attribute characteristics should be utilized in a quality assurance evaluation of theexternal data.

88 ACCURACY AND FINAL ACCEPTANCE CRITERIA

Acceptance criteria determine to what standards data must comply in order to be usable within thesystem. Graphic acceptance standards for external digital data may be identified in three differentcartographic quality types which include: relative accuracy, absolute accuracy and graphic quality.Standards for GIS data will normally depend upon the accuracy required of the dataset. In the GISenvironment, accuracy will depend upon the scale at which the data is digitized, and at which scaleit is meant to be used.

• Relative accuracy is basically a measure of the normal deviation between two objects ona map and is normally described in terms of + or - the number of measurement units(normally inches or feet) the feature is located apart from its neighboring map features,as compared to their locations in the real-world.

• Absolute accuracy criteria will evaluate the measure of the maximum deviation betweenthe location of the digital map feature and its location in the real-world. Manyorganizations set their absolute accuracy standards based upon National Map AccuracyStandards.

• Graphic Quality refers to the visual cartographic display quality of the data, and pertainsto aspects such as the data’s legibility on the display, the logical consistency of mapgraphic representations, and adherence to common graphic standards. Placement andlegibility of annotation, linework, and other common map elements all fall undergraphic quality.

Informational quality is another accuracy criteria component which should be given much attentionin building a database. Informational quality relates to the level of accuracy for both map graphicfeatures and to their corresponding tabular attribute data. There are four basic categories forassessing these qualities:

• completeness• correctness• timeliness• integrity


Together, these aspects of informational quality comprise the extent to which the dataset will meetthe basic requirements for data conversion acceptance.

Completeness is an assessment of the dataset’s existing features against what should currently belocated within the dataset. Completeness may relate to a number of digital map features:annotation symbols, textual annotation, linework. Completeness will also relate to the attributedata, and whether all of the necessary attributes are accounted for. A typical requirement for thebottom limit of dataset completeness, when outsourcing conversion, is that not more than 1% ofthe required features and attributes will be missing from the digital dataset. For example, out of 80roads that are located within a geographic area, if only 72 are included on the map, then only 90%of the data is included, and thus the map is only 90% complete.

Correctness is that quality which relates to the truth and full knowledge of the informationcontained. If a map shows a number of roads, and the linework is positioned correctly, but is notlabeled correctly, there is a problem with correctness. Correctness applies both to map featuresand to attribute data. If a dataset has the positional accuracy, or the completeness in terms ofplacing an object, but does not have the correct label for that object, this is a problem with thecorrectness of the dataset. Evaluating correctness can be done through automated or manualprocedures. Validation procedures are those which would be utilized in the testing of the datasets.An example of assessing correctness might include the matching of one dataset source againstanother to check for data accuracy from the various matching qualities. Every graphic and databasefeature has the potential for error.

Timeliness is another measure of informational quality, and it is a unique form of correctness.Timeliness is based upon the currency of a dataset, and if it is not up-to-date, or current, then thedataset must be of a specified age. The timeliness of a dataset begins from the date the datasetarrives at the client’s door. From that point on, it is the responsibility of the client organization tomaintain the data, and its currency.

The integrity of a dataset is a measure of its utility. Graphically, database integrity means that thedataset is maintaining its connectivity and topological consistency. In it, all lines are connected,there are no line overshoots or undershoots, and all feature on the display are representative of real-world features. In order to maintain database integrity, there should not be any missing orduplicate records or features.


GIS DEVELOPMENT GUIDE: PILOT STUDIES ANDBENCHMARK TESTS

11 INTRODUCTION

Prior to making a commitment to a new technology like GIS, it is important to consider testingconcepts and physical designs for development of such a system within a local government. Thiscan be done by performing a pilot study to determine if GIS can be useful in the daily conduct ofbusiness and, if so, further conducting a benchmark test to determine the best hardware andsoftware combination to meet specific needs.

Numerous GIS pilot studies and benchmark tests have been conducted by local governmentswithin the state and across the nation. Decisions on deployment of GIS should not be based solelyon other experience. Managers and end users respond best to relevant local data and actualapplications, and will learn more readily if they have first hand experience defining and conductinga pilot study on benchmark test in-house.

22 PILOT STUDY: PROVING THE CONCEPT

Planning a Pilot Study

A pilot study provides the opportunity for a local government to evaluate the feasibility ofintegrating a GIS into the day-to-day functions of its' operating units. Implementing GIS is amajor undertaking. A pilot study provides a limited but useful insight into what it will take toimplement GIS within the organization. Proving the concept, measuring performance,and uncovering problems during a pilot study, which runs concurrent withdetailed system planning, database planning, and design, is more beneficial thanpressing forward with implementation without this knowledge.

To maximize the usefulness of the pilot study, it must be planned and designed to match theorganizations work flow, functions, and goals as described in the GIS needs assessment. Thepilot study will be successful if it has the support and involvement of upper management and stafffrom the outset. This involvement will provide the opportunity to evaluate management and staffability to learn and adopt new technology.

Objectives of a Pilot Study

A pilot study is a focused test to prove the utility of GIS within a local government. It is not a fullGIS implementation nor is it simply a GIS demonstration; but rather a test of how GIS can bedeployed within an organization to improve operations. It is the platform for testing preliminarydesign assumptions, data conversion strategies, and system applications. A properly planned andexecuted pilot study should:


• create a sample of the database• test the quality of source documents• test applications• test data management and maintenance procedures• estimate data volumes• estimate costs for data conversion• estimate costs for staff training

The pilot study should be limited to a small number of departments or GIS functions and a smallgeographic area. The pilot study should be application or function driven. Even though dataconversion will take a major portion of the pilot study development time, it is the use of the datathat is important. What the GIS can do with the data proves the functionality and feasibility of GISin local government. The Needs Assessment document has identified applications, data required,sources of data, etc. In addition, a conceptual database design has been previously developed.Following is a list of procedures for carrying out a pilot study:

• select applications from needs assessment• determine study area• review conceptual database design• determine conversion strategy• develop physical database design• procure conversion services and develop conversion work plan• commence source preparation and scrubbing• develop acceptance criteria and qc plan• develop data management and maintenance procedures• test application• evaluate and quantify results• prepare cost estimates

Selecting Applications to Include

Care must be taken to select a variety of applications appropriate to test the functional capabilities ofGIS and the entire database structure. A review of the Needs Assessment report should provideselective applications to meet these requirements. Make sure to include data administrationapplications along with end user/operations applications. Data loading, backups, editing and QCroutines have little user appeal, but they represent important functions that the organization will relyon daily to update and maintain the GIS database.

Selecting Data

Data to be tested in the pilot study can either be purchased from external sources or converted fromin-house maps, photos, drawings, documents and databases. In any event, the data shouldrepresent the full mix and range of data expected to be included with the final database. It shouldinclude samples of archived or legacy system records and documents if they are planned to beincluded in the GIS in the future. All potential data types and formats should be considered for thepilot. This is the chance to test the whole process of integrating and managing data, together with


the utility of the data in a GIS environment and different conversion and compression methods,before final decisions are made.

Spatial Extent of the Pilot Study

Selection of the study area should address several issues:

• Data density• Representative sampling• Seamless vs. sheet-wise conversion or storage

Choose an area (or areas) of interest that represents the range of data density and complexity.Make sure that all data entities to be tested exist in the area of interest. This will provide arepresentative dataset and allow the extrapolation of data volumes and conversion costs for therange of data over the entire conversion area.

To measure hardware performance the selected area should be chosen to match the file or mapsheet size the end user will normally work with. Be aware that even if the data is currentlyrepresented as single map sheets at a variety of scales, the GIS will store the data as a "seamless"dataset.

Preliminary Data Conversion Specifications

A set of data conversion specifications need to be defined for each of the required data layers in thetest datasets. The conversion specs need to address....

• Accuracy • Reliability• Coverage • Convenience• Completeness • Condition• Timeliness • Readability• Correctness • Precedence• Credibility • Maintainability• Validity • Metadata

The foundation of the GIS is derived from the conversion process which creates a topologicallycorrect spatial database. The following diagram identifies in detail the steps necessary to create thisdatabase.


Steps in creating a topologically correct vector polygon database

FIELD DATA

NON-SPATIALATTRIBUTES

SPATIALDATA

INPUT TO TEXT FILE

MANUAL DIGITIZING

DIGITIZESCAN AND VECTORIZE

SCANNING

linked by unique

indentifiers

VISUAL CHECK

CLEAN UP LINES AND JUNCTIONS

WEED OUT EXCESSCOORDINATES

CORRECT FORSCALE AND

WARPING

ADD UNIQUEIDENTIFIERSMANUALLY

CONSTRUCTPOLYGONS

LINK SPATIALTO NON-SPATIAL DATA

TOPOLOGICALLY CORRECTVECTOR DATABASE OFPOLYGONS

Figure 1 - Source: Principles of Geographic InformationSystems for Land Resources Assessment, Burrough, P .A. ,

1986.

Selecting GIS Hardware and Software

To provide for continuity and to minimize added expense for total system development, select themost likely choice of hardware and software based on the database design specifications, andpurchase or borrow that necessary for the pilot study from the hardware and software vendors.

Selecting a Data Conversion Vendor

Even though this is only a pilot study, it also serves as a test of likely suppliers of hardware,software and data conversion services. Therefore, a respectable data conversion vendor should beselected to perform the work, and prior uses of the vendor services should be contacted to confirmtheir ability to meet expectations. It shouldn't matter what method the conversion vendor uses toconvert the data. Be open to suggestions from the potential conversion vendors as to the most costeffective methods to convert the data. As long as you get the data in the correct and usable formatto satisfy your database plans, the method for data conversion used should not be an issue.


However, you will get much better results if the vendor has first hand experience with the chosenGIS software and the data conversion takes place in the same GIS software package. There isalways a chance of losing attributes or inheriting coordinating precision errors converting from oneformat to another.

Defining Criteria for Evaluating the Pilot Study

The pilot study performance must be evaluated in measurable terms. By its very name, a pilotstudy implies an initial investigation. An investigation implies a set of questions to ask and a set ofanswers to achieve. For clarity, the questions can be addressed to match the major component ofGIS plus others as needed.

Database

• Were adequate source documents available and was their quality sufficient?• How much effort was involved in "scrubbing" the data before conversion?• How long did the conversion process take?• Were there any problems or setbacks?• Was supplemental data purchased, if so, what was the cost?• Did the data model work for each layer as defined?• Was the data adequate (i.e. all data elements populated)?• What errors were found in the data (closure, connectivity, accuracy, completeness,

etc.)

Applications

• Were the applications written as specified• Did the applications fit smoothly in the GIS or was a separate process invoked?• Are the required functions built into the GIS or will applications need to be developed?• Is the GIS customizable?• How responsive and knowledgeable is the software developer's technical support staff?• Were expectations met?

Management and Maintenance Procedures

• How will the data be updated, managed, and maintained in the future?• Have all those who will contribute to the updating and maintenance been identified?• Have data management and administration applications been developed and tested?• Have data accuracy and security issues been addressed?• Who will have permission to read, write, and otherwise access data?• How will using GIS change information flow and work flow in the organization?

Costs


• How large a database will be created?• What will be the required level of existing staff commitment during the data preparation

and GIS construction process?• What will be the cost for data conversion of in-house documents?• What will be the cost for obtaining supplemental data from outside sources?• How will GIS impact or interface with existing hardware and software?• What new hardware, software and peripheral equipment is required?• How much training of staff is required?• Will additional staff with distinct GIS programming and analysis capabilities be

required?

33 EXECUTING THE PILOT STUDY

Data Preparation (Scrubbing) and Delivery

Document preparation of source data representing the entire range of data to be included in thedatabase must be completed before the conversion contractor can begin work. Data preparationincludes improving the clarity of data for people outside the organization who are unfamiliar withinternal practices. This pre-conversion process is referred to a "scrubbing."

Scrubbing is used to identify and highlight features on maps that will be converted to a digitalformat. The process provides a unique opportunity to review or research the source and quality ofthe documents and data being used for conversion.

AIdentify



IdentifyAppropriate

Data Sources


Design

DetermineConversion

Strategy


Design

ProcureConversion

Services

IdentifyAccuracy

Requirements


CommenceSource


CommenceOther

In-HouseActivities


QC Plan

EditDelivered

Data

CommenceDatabase

Maintenance

DevelopDatabase


Figure 2 - Guide to Data Conversion Source: GIS Data ConversionHandbook


Scrubbing is generally an internal process, but may also be performed by the conversion vendor.The conversion vendor will need to be trained on how to read your maps or drawings. The firstmap (or all maps) may need to be marked with highlighter pens and an attached symbol key todefine what features need to be collected.

At the same time the maps are marked-up, coding sheets are filled out with the attributes of thefeatures to be captured and a unique id number is assigned to both the feature and the coding sheetto create a relate key. This key is critical to connecting the attribute records to the correct mapfeature defined in Database Design.

The best key is a dumb, unique, sequential number that has no significance. The key should neverbe intelligent, that is contain other information. The key should never be a value that has meaning,or has the potential of changing. Don’t use address, or map sheet number or XY coordinates ordate installed. These values are very important and should each have their own field in thedatabase. Don’t use them as the primary key. The reason is very simple. If you use a smart keylike SBL number and you have to change the number, you run the risk of losing the connection toall other related tables that key on the SBL number. Make the change and the records no longermatch. However, if the key is unique and has no meaning it will never have to be changed. Streetnames change, numbers get transposed, features are discovered to be on the wrong map sheet or atthe wrong XY coordinates. If any corrections need to be made, a large defensive programmingeffort must be in-place to guarantee the integrity of the intelligent key. Avoid the grief and use adumb, unique key.

Coding sheets are only required if the attributes of the features are not readily available from themap document. For example, if all the required attributes for a feature are shown as annotations onthe map (e.g. the size, material and slope for a sanitary sewer line), then a coding sheet isunnecessary. If additional research is required to find the installation date, contractor name, flowmodeling parameters or video inspection survey, then a coding sheet needs to filled out for eachfeature. Again it is critical to create and maintain a unique key between the map feature and theattribute data on the coding sheet.

Once the data has been prepared for conversion, make copies of everything being sent out andmake an inventory of the maps, coding sheets, photos, etc. that will be sent to the vendor. Ask thevendor to perform an inventory check on the receiving end to verify a complete shipment arrived.

Change management is essential. If the manual maps or data will be continually updated in-house during the conversion process, keep careful records about what maps and or features havechanged since the maps have been sent out. This is an important process that needs to be fully in-place if the pilot study leads to a full GIS implementation.

When and Where to Set Up the Pilot Study

Expect the pilot study to have an impact on daily work. Choose participants where the pilot willnot have a negative impact on the daily workload. Even if the GIS is to assist a mission criticalprocess like E911, conduct the pilot as a parallel effort, don’t expect it to replace an existingsystem. At the same time try to make the GIS a part of the daily workflow to test the integrationpotential.


To ensure some level of success of the pilot study, choose willing participants to act as the test bed/pilot study group. Make sure they understand the impact the pilot will have on the organizationand the level of commitment from the staff members. Use educational seminars to inform theemployees about GIS technology and the purpose of the pilot study. Communicate very clearlywhat the objectives of the pilot study will be, what functions and datasets will be tested and whichquestions will be investigated. Describe the required feedback and the use of questionnaires orchecklists that will be used. Above all else, communicate to keep staff informed and to controlexpectations.

Who Should Participate

A team representing a cross-section including managers, supervision, and operations staff shouldbe assembled for the pilot study. Choose the staff carefully to assure objective and thoughtfulsystem evaluation. If possible, choose the same people that were involved in the needs assessmentprocess. They will be more aware of GIS technology and may be eager to see the project moveforward.

Testing and Evaluation Period

Have a pilot team kickoff meeting with the conversion / software / hardware vendors present.Restate the objectives of the pilot study and responsibilities of each party. Review NeedsAssessment, database design documents and assess training requirements. Define communicationprotocol guidelines if necessary to keep key players communicating and resolving problems.

Before the data arrives, install the software and or hardware in the target department. Conduct usertraining to familiarize employees with the use of the GIS software. If employees are unfamiliarwith computers, allow more time for training and familiarization.

Once the data has been converted and delivered, have the conversion vendor or the softwarevendor load the data on the target machines. Be sure that this step and all preparatory efforts aremonitored and treated as a learning process for your staff.

Begin a through investigation of the capabilities and limitations of the hardware and software.Keep user and vendor defined checklists beside the machines at all times. Have each user log theirobservations and impressions with each session. Make sure to note any change in performance asa function of time of day or workload. Also note if the user’s level of comfort has increased withtime spent using the software.

Log all calls to the data conversion, software and hardware vendors. Note the knowledge and skillof the call takers, responsiveness and turn-around time from initial call to problem resolution.Some problems may be addressed on the phone, others may take days. If the call cannot behandled immediately, ask the outside technical support person for an estimated time.

Obtaining Feedback From Participants


It is imperative that all individuals involved in the pilot study provide input before during and afterthe pilot study is complete. The best method to guarantee feedback from the participants is to havethem help formulate the objectives of the pilot, the questionnaires and checklists. Samplequestions to address were listed earlier in this document. Augment these with questions from yourown staff. Some questions can be answered with a yes/no checklist, some answers will be a dollarfigure, and some will require a scoring system to rate aspects of the system performance fromsatisfactory to poor or unacceptable. Other issues that may effect information flow, traditionalprocedures and work tasks will require participants to write essay questions or draw sketches ofchanges they would like to see in the user interface or in the map display. All responses should becompiled in such a way that the responses can be measured and rated numerically.

44 EVALUATING THE PILOT STUDY

What Information Should Be Derived From the Pilot Study

The first question to be addressed is whether the pilot study was a success. Success doesn’tnecessarily mean that the process went without a hitch. A successful pilot study can be fraughtwith problems and GIS can be rejected as a technology for the organization. The success of thepilot study should be measured by whether the goals and objectives defined for the pilot wereachieved. Most issues listed below were covered in earlier portions of the document, but aresummarized again.

Data Specific Issues

Many issues to be assessed in the pilot study are data specific and are related to data quality,volumes and conversion efforts.

Source Document Quality

Most first time GIS users are so awe struck by seeing their maps on the computer screen oron colorful hard copy plots that they overlook the importance of reviewing the quality andusefulness of the source documents and the utility of the final product. Many original mapsare so old and faded, that they are unusable as a source document to create a GIS dataset.Some municipal agencies have scraped the existing maps and re-surveyed the entire town’sstreet and utility infrastructure. This is not a cheap alternative, but digitizing bad maps isnot a good investment.

Quality Control Needs

There is a danger present in any data conversion project (even for a pilot study) that thevendor will perform the conversion and deliver the data to the client without an adequateQuality Control process in place. If the client is new to GIS, they may not be able todetermine if all the data is present, if the data is layered correctly or if all attributes arepopulated.


Because a GIS looks at map features as spatially related, connected or closed features, GISquery and display functions can be used to identify features that are in error. By displayingeach map layer one at a time using the attributes of the features, item values that are out ofrange (blank, zero, or extreme values) will show up graphically on the maps in differentcolors or symbol patterns. Erroneous values should be reported to the conversion vendorimmediately for resolution.

The client may consider using a third party GIS consulting firm to review the quality of thedata and verify the map accuracy.

Data Availability

Before an attribute field is added to a coding sheet as a target for data capture, be sure thevalue is readily available and has importance to the operation of the agency. Many datafields would be nice to have, but may not be cost effective. For example, a sidewalk anddriveway inventory for a community would be a useful data layer to capture. However, ifthere are no existing maps showing sidewalk locations, using aerial photos andphotogrammetry is a costly approach to capture sidewalks and driveways. A cheaperalternative may be to create two single digit fields in the street centerline attribute table tohold flags indicating the presence or absence of sidewalks on the left or right side of thestreet. An operator looking at the GIS screen and air photos can assign the values to theflags without a large amount of effort. Based on these values, different line styles or colorscan be used to symbolize the presence of sidewalks in a screen display or hardcopy maps.

Pre-conversion Editing

Be sure to track and review the number of man hours and problems encountered during thepre-conversion scrubbing effort. These steps will undoubtedly be performed again duringthe full conversion and now is the time to assess the impact on the organization.

Data Volumes

Data volumes and disk space is an important issue to evaluate in the pilot study. The pilotby design covers a small area of interest. Use the same data cost ratios discussed above toextrapolate data volumes for the entire GIS implementation effort. Data volume is not onlya disk space issue. There are inherent problems associated with managing large datasets.Large files take more computer resources to manipulate, backup, restore, copy, convert,etc. A tiling scheme (i.e. breaking the data into smaller packets for storage andmanipulation) should be investigated in the pilot study as a future solution for fullimplementation.

Assessing the Adequacy of the Data Conversion Specifications

Data conversion specifications are provided to give the conversion vendor and the clientorganization a set of guidelines on what layers, features and attributes should be captured, at what


precision, level of accuracy and in what format is the data to be delivered. Best intentions andreality need to meet in the pilot study to evaluate the expectations and the level of effort (costs)involved with converting the target dataset.

Ask the conversion vendor for feedback on the clarity of the specifications. Do the specs makesense? Some vendors, holding to the adage “the customer is always right”, will not question yourspecifications and will do whatever you ask no matter how in-efficient the process. Others willopenly suggest alternatives approaches and will seek clarifications. Note the kinds of questionsthey present and be open to changes early in the process.

Evaluation of logical data model and applications

Not only should the quality of the data conversion and the GIS software be reviewed in thepilot, but just as important, the logical data model needs to be reviewed. The logical datamodel describes how map features are defined (points, lines, polygons, annotations) andthe relationships between these map features and related database tables. Runningapplications against the data model will allow measurement of response time that is afunction of data organization.

The bottom line is does the data model make sense for all the applications being addressedin the pilot and will it be useful in the full implementation. Ask the conversion and softwarevendors to explain the organizational structure of the GIS data model. What are theadvantages, disadvantages and tradeoffs for the model used in the pilot and ask if the samestructure would work comparably in a full implementation. Look carefully for short cuts ordata model changes to make a dataset work in the pilot. It may work very well for a demoon a small dataset, but it may be unwieldy in a large implementation.

GIS hardware and software performance

Test the GIS running under a variety of scenarios ranging from single to multiple usersperforming simple to complex tasks. Ask your software vendor to write a simple macro tosimulate multiple users running a series of large database queries. Test the performance ofquery and display user applications while data administration functions are running.

Were the users able to learn to use the system and perform useful work?

Refined GIS Cost Estimates

By requiring the conversion vendor to keep detailed logs of conversion times foreach data layer and feature type by map sheet, the client organization can projector extrapolate from the pilot data conversion to a cost for full conversion. One approachthat has work well in the past is to use parcel density as an indicator of manmade features.For example, if you compute a series of ratios of the number of buildings, light poles,miles of pavement edge, manholes, hydrants, and other features against the number ofparcels in the pilot area, you can compute with pretty good certainty the number ofmanmade features in the remainder of the GIS implementation area. The Office of Real


Property Services has a low cost ($50 / town) parcel centroid database in a GIS format thatcan be used as a guide for parcel density. Unfortunately physical features like streams,ponds, contours, wooded areas, wetlands, etc., do not have a direct correlation to parcels.In fact there seems to be an inverse relationship between parcel density and number ofphysical features. The point to be learned is that the pilot study should provide anindication of costs for a full featured/full function GIS implementation effort.

Analyzing User Feedback

Tally the number of positive responses to yes/no questions, compute an average score for usersatisfaction, and compile the essay responses for content and tone. Review the complied resultswith all team members and management. Interview team members to clarify questions with unclearor strong responses to gain more insight. From response scorecards and comments develop anoverall score to determine user satisfaction, completion of goals and objectives.

55 BENCHMARK TESTS: COMPETITIVE EVALUATION

The purpose of a benchmark is to evaluate the performance and functionality of different dataconversion methods, hardware and software configurations in a controlled environment. Eachsoftware package can be compared in the same hardware environment or one software package canbe compared across different hardware platforms.

By defining a uniform set of functions to be performed against a standard dataset, key advantagesand disadvantages of the different configurations can be compared fairly and objectively.

Planning a Benchmark Test

As with any successful project, a detailed, thought out plan needs to be devised. It should benoted that performing a benchmark takes a large amount of effort by both the local governmentagency and the vendors taking part. Few firms can afford to devote large amounts of staff timeand computing resources competing in benchmark tests for free. Keep that in mind as you designthe benchmark to focus the tests on key issues that can be readily compared. If the benchmark willbe extensive, associated costs may be incurred.

Objectives for the Test

A benchmark provides an opportunity to evaluate the claims of advanced technology and highperformance presented by the marketing/sales force of competing data conversion, hardware andGIS software vendors.

The objectives of the benchmark should be defined clearly and communicated to all partiesinvolved. Suggested objectives for each of the different types of benchmarks include testing:

Conversion Methods• Cost effective procedures


• Sound methodology• Quality control measures• Compliance with conversion specifications

Hardware• Computing performance• Conformance to standards• Network compatibility and interoperability• Future growth plans and downward compatibility

Software• Conformance to standards• Computing speed / performance• GIS functionality (standard and advanced)• Can the software run on your existing hardware system• Ease of use - menu interface, on-line help, map generation, etc.• Ease of customization for non-standard functions• Licensing and maintenance costs

This list of objectives is not all inclusive and should only be used as a guideline or a starting pointfor your organization to design a benchmark study.

Preparing Ground Rules

Based on the defined objectives, all parties involved should be aware of what will be tested, howthey will be judged and what criteria will be used as a measure (i.e. low cost, high performance,good service, quality, accuracy, etc.).

• Tests to be performed should be as fair as possible• The exact same information and datasets should be given to all vendors• A reasonable time frame should be provided to perform the work• No vendor should be given preferential treatment over any other and clarificationsof intent should be offered to all• Tests should be quantitatively measurable• Hardware tests should use comparably equipped or comparably priced machines• Software tests should be performed on the same hardware and operating system

Create scoring sheets for each aspect of the test. For subjective tests, like ease of use, have eachuser rate their satisfaction/dissatisfaction with the results of each phase using a numeric rank-orderscheme. This won't eliminate bias but will allow impressions and opinions to be compared. Forobjective tests, like machine performance, record the clock speed, disk space requirements,number of button clicks, error messages, response time, etc. for each test conducted.

Preparing the Test Specifications (Preliminary Request for Proposals or RFP)

The test specifications need to outline the type of test to be conducted (conversion, hardware orsoftware); objectives of the test; detailed description of the test; measures for compliance; and atime frame for completion.


Selecting the Participants and Location

In order to conduct a benchmark, you need knowledgeable participants (both internal and external).The internal participants should be knowledgeable regarding the topic to be tested (data conversion,hardware or software).

Selecting external participants is more involved. Situations range from not knowing any vendorsto invite to how to limit the number of vendors. The smaller the number of participants the easierthe final selection process will be for the local government agency.

The Request for Qualifications (RFQ) process can be used to filter or pre-qualify potentialparticipants. GIS is a specialized field and not every business involved with computers isqualified.

Several factors should be considered when selecting vendors for a benchmark test

• Are they knowledgeable about local government agency operations• Are they a well known company• Are they technically qualified• Are they experienced and have a successful track record• Are they financially sound, insured or bonded• Are they going to be around 5 years down the road• Are they local or do they have a local representative• Would their previous clients hire them again

If the RFQ and/or the RFP are written clearly and succinctly, the process will filter the participantsand only those companies that specialize in the subject in question will respond.

The benchmark can occur either at the client’s site or the vendor’s offices. Some tests like dataconversion are best conducted at the vendor site to minimize relocating staff and equipment for atest. Hardware and software benchmarks are commonly conducted at both the vendor and clientsite. The initial data loading, customization and testing is performed at the vendor site. Once theoperations are stable, the client is invited to view the results at the vendor site, or the system istransported to the client site.

Preparing the Data

For a data conversion benchmark, provide each vendor with a set of marked up (scrubbed) set ofmaps, documents and coding sheets as described in the pilot study section above. If possible,provide the data conversion vendor with an example dataset from the pilot study which shows theappropriate data layering, tolerances and attributes to be captured. If not a dataset, clearspecifications for how the data should appear when complete. Specify what data format (*.dxf,*.e00, *.mif, tar, zip, etc.) and what type and size of media (1/4”, 8mm or 4mm tapes) you wantthe data delivered in.


For a hardware or software benchmark, provide a sample dataset which contains all possible layersfor inclusion in the GIS. The data could be purchased, converted during the pilot study or couldbe the results from a data conversion benchmark noted above. Provide sufficient documentationwith the data to describe the use of the data, the organizational structure and contents.

Scheduling The Benchmark Test

Once the benchmark has been defined and agreed to by the participants, set a time for the testing tooccur. Schedule a start date and a duration. Unless you specifically want to use companyresponsiveness as part of the test (i.e. how fast can they respond to a problem), don't require animmediate start date or extremely short time frame. There is no need to cause undue panic andstress, you want a good test.

Transmitting Application Specifications And Data To Participants

Before transmitting maps, documents or data to any vendor, make an inventory and backup copiesof all items. Either specify to the vendors that the data will be provided in a single data format on aspecific media, or make arrangements to provide the data in a format they can read. Be sure to testthe readability of the tape or disk on a target machine in your office before sending the data out.Once the data has been verified as complete and readable, make two copies of the tapes ordiskettes, one to send and one to keep as a recoverable backup for documentation of the delivery.Provide detailed instructions as to the contents of the tapes or disks and how to extract the data.List phone numbers of responsible persons should problems arise with delivery or data extraction.Ask the vendor to perform an inventory at the receiving end to acknowledge receipt of the data ordocuments.

On-Site Arrangements

If the tests are to be conducted at your site, make sure you have the authorization and backing ofmanagement and all personnel to be involved. Provide plenty of advanced notice and time tosetup. If you are conducting hardware tests you have to decide if more than one vendor'smachines will be present at the same time for comparative testing. With both machines setup in thesame room, you can conduct the exact same tests in "real time" and visually compare the results,but this will require more setup space and logistic leeway in the schedule to accommodate multiplevendors. Make sure you have a suitable environment for equipment with adequate power, airconditioning and security. Also make sure you have all required utility software in place to readand write compressed files from tape and virus detection software.

If you are performing software tests, make sure you have two or more machines with the exactsame hardware and operating system configurations. If you can't have multiple machines, be sureto backup and restore the current operating system files before testing each software package toensure a fair test of disk space requirements, resource usage and functionality. Always use thesame datasets for each test.

Identifying Deficiencies In Specifications

Although the tests were well thought out and carefully followed, you will probably wish you hadperformed additional tests during the benchmark. If short comings are discovered early on andthey do not involve major changes in direction, additional tests could be incorporated. Be sure tonotify the local management, staff and vendor participants of the change in objectives.


Defining benchmark criteria

Data Conversion Issues

A standard set of tests need to be performed to evaluate the results of a data conversion benchmark.Overlaying checkplots with the source documents on a light table is a straightforward but timeconsuming way to compare the conversion results. Suggestions made in the Pilot Study section ofthis document, outline methods for using GIS query and display functions to determine if all thedata is present, layered correctly and attribute values are within range. Displaying map features byattributes will highlight errors or items out of range in different colors or symbol patterns.

GIS Software Performance

Software tests can be classified into 2 groups - capabilities and performance. Capabilities tests ifthe software can perform a specific task (i.e. convert DXF files, register image data, accessexternal databases, read AutoCAD drawings, etc.) Performance deals with how well or how fastthe software performs the selected task. How fast can be measured with a stopwatch, how well isopen to interpretation.

The operating system on the machines in question will play a big factor in how GIS software willperform. GIS software written to run on a 32 bit operating system will not perform as well in a 16bit environment without work arounds. Likewise, a 16 bit application will run faster on a 32 bitmachine, but will not run as well as 32 bit software on a 32 bit operating system like UNIX,Windows 95 or Windows NT.

Hardware Performance

The goal is to find the fastest, cheapest hardware to meet your budget. Take advantage of computermagazine reviews of hardware. They conduct standard benchmark tests involving wordprocessing, spreadsheets and graphics packages. The test results won’t be GIS specific, but willshow the overall performance of a given computer. Oddly enough, two computers with seeminglyidentical hardware specifications (clock speed, memory, and disk space) can perform verydifferently based on internal wiring, graphics acceleration and chip configurations.

Evaluating Benchmark Results

If the questions were formulated clearly, and the results were recorded honestly, evaluating theresults of the benchmark should be process of simple addition. Essay responses and commentswill have to be followed up with further tests to clarify any problems or differences encountered.

Departments and Functions which will Utilize GIS Type of Use

General Descript ion ofGIS Map Products and

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Sanitary Sewers • • • • • • • • • • • • • •

Pump Stations & Force Mains• • • • • • • • • • • • • •

Water Lines • • • • • • • • • • • • •

Storm Sewers • • • • • • • • • • • • • •

L ight ing • • • • • • • • • • •

District Boundaries • • • • • • • • • • • •

Easements • • • • • • • • • • • •

Street Map • • • • • • • • • • • • • • • • • • •

Streams & Ditches • • • • • • • • • • • • •

So i l s & Rock • • • • • • • •

Wetlands • • • • • • • • • •

Woodlands • • • • • • • • •

Archaeo log ica l S i te s • • • • • • • • • •

Hazardous Materials Sites • • • • • • • • • • • • • • • • • • • •

Crit ical Environmental Zones• • • • • • • • • •

Drainage Basins • • • • • • • • • • •

Tributary Areas • • • • • • • • • • • • •

Sewer Flow Analys is • • • • • • •

Sewer Capacity Analys is • • • • • • •

Scheduled Repair Work • • • • • • •

Emergency Repair Work • • • • • • • •

Dispatch • • • • • • • • • •

Route Se lect ion • • • • • • • • •

Bui lding Types • • • • • • • • • • • • • • • • • •

Crimes • • • • • • •

Fires • • • • • • • • •

Subd iv i s i ons • • • • • • • • • • • • • • •


Volume III

Table of Contents

ACQUISITION OF GIS HARDWARE & SOFTWARE

Introduction .....................................................................................1GIS Hardware and Software Acquisition................................................2Steps in the GIS Acquisition Process......................................................2Evaluation of Proposals........................................................................4GIS Delivery and Installation Plan.........................................................6Sample Hardware Specifications............................................................6Network and Communications Specifications..........................................9Software Specifications ......................................................................10GIS Database Structure ......................................................................13Summary ...................................................................................14

GIS SYSTEM INTEGRATION

Introduction ...................................................................................15GIS System Components.....................................................................15System Testing..................................................................................18User Training ...................................................................................18

Figures1 - Database Integration .................................................................162 - Library Structure to Support Editing..........................................173 - System Integration....................................................................18

GIS APPLICATION DEVELOPMENT

Introduction ...................................................................................19Why Applications are Needed.............................................................19Categories of Applications..................................................................19Database Applications ........................................................................21

Figure

1 - Life Cycle of a GIS Database.....................................................20

Table of Contents cont'd

GIS USE & MAINTENANCE

Introduction ...................................................................................22User Support and Service...................................................................22Data Maintenance Procedures .............................................................23Examples ...................................................................................28

Figure

1- Overview of GIS Maintenance ...................................................24

GIS DEVELOPMENT GUIDE: ACQUISITION OF HARDWAREAND SOFTWARE

11 INTRODUCTION

This guide begins the description of the first of four steps of the GIS Development process (figure1) which deal with the actual assembly of the GIS and its subsequent operation.

NeedsAssessment

ConceptualDesign


H/W & S/WSurvey

Pilot/Benchmark








All of the necessary planning, design and testing should have been completed during the executionof the previous seven steps of the GIS development process. The remaining steps and their mainpurpose are as follows:

• GIS Hardware and Software Acquisition - includes the final selection of the hardwareand software (by competitive bid in response to a Request for Proposals - RFP, asnecessary); the delivery and installation of the hardware and software; and all necessaryrenovation of space, wiring, and environmental remodeling.

• GIS System Integration - bringing the final database and the hardware and softwaretogether and testing their combined operation.

• GIS Application Development - preparing applications identified in the NeedsAssessment which require additional programming using the GIS macro language orother supporting programming languages.

• GIS Use and Maintenance - starting use of the GIS and institution of database,hardware and software maintenance programs. Further application development anduser training are also continuing needs.

22 GIS HARDWARE AND SOFTWARE ACQUISITION

This step is the actual purchase of the GIS - hardware and software. The GIS to be acquired isusually subject to competitive bid by the interested vendors. The single most critical part of thisprocess is the preparation of an adequate (and detailed) Request for proposals (RFP).

Acquiring the components for your GIS is an important step. Use all of the information you havegathered up to this point to produce a document telling prospective bidders what you need. Thedocument should clearly communicate your needs and how bidders should respond to the RFP.

During this phase remain objective. Keep as much of the “politicking” out of the selection process.You should be looking for the best value for your money, not the lowest cost.

33 STEPS IN THE GIS ACQUISITION PROCESS

Evaluation Team

The evaluation team should be made up of interested staff from departments involved inimplementing GIS within the local government. These individuals need to be objective and nothave pre-defined ideas of what system they want. They need to be action oriented and willing toput in the time to do the job right. A successful RFP process involves a great deal of hard workand coordination. You will need to have people on the committee to help accomplish this.

Once a draft RFP has been developed, have an objective 3rd party look at it. You want it ascomplete and readable as possible. This can be another local government (maybe one of the oneshow supplied you a copy of theirs) or a consultant helping you with the RFP process (make surethe consultant is not planning on bidding on the project).

Preparation of Request for Proposal (RFP)

The RFP document is used to communicate your needs to potential bidders. It will also tell biddershow you want them to respond to the RFP.

Be as specific as possible in defining what you need for your GIS. Provide detailed descriptions ofthe functionality, services and support you are looking for. It is recommended that you do not usespecific brand names of software and hardware products in your RFP specifications. This willlimit the number of potential bidders you can choose. There will be situations where specific

products are needed. An example is when your organization has a policy in place for using a typeof operating system or has already standardized and developed data sets for use in a particularsoftware package. Focus more on what you want the system to do. You will not get what you needunless you specify it clearly in the RFP.

In your RFP, tell the bidders how you want them to respond. Provide examples of what you want:define how pricing should be structured, use standardized forms if appropriate, clearly state criteriafor evaluating the responses. You will receive responses that are more consistent and easier toevaluate if you define the response guidelines in the RFP.

To get started, contact other local governments who have recently developed similar RFPs. Usethese as a guide. It would be a good idea to contact the person responsible for evaluating theresponses. Ask them what worked and what didn’t work with the RFP. Adjust your RFPaccordingly. Also adjust the scope of your RFP to fit your needs. If you are a small village, don’tuse a RFP developed by a larger city (or visa-verse) you will not get what you need and thepotential bidders will be confused or mis-directed.

Distribution of RFP

You will want your RFP to go to qualified bidders. The best source for this is to go to trade showsor GIS user group meetings and ask around. Again, try to stay objective. Don’t get mis-lead byflashy demos or excessive hype. Talk to other local governments and get recommendations ofcompanies they think are qualified to respond to your RFP.

Another method might be to post a notice in GIS trade journals (both regional and national). Beprepared for a large amount of companies inquiring about your project. This method is better usedfor large, expensive projects.

Bidder’s Meeting

A bidder’s meeting should be scheduled within a week or two of the RFP be sent out. Make surethe time and location is in the RFP. This meeting is used to get feedback from the bidders and toclarify anything not clearly stated in the RFP. It is always an interesting experience to have numberof competitors gathered together in one room. There will be a reluctance by the bidders to ask anyquestions that might give away their bidding strategy to their competitors. Do not be surprised ifthere are not many questions raised at the meeting. To get things going, have a short preparedstatement or presentation that outlines the history of the project and the requirements of the RFP.

It is important to ask the bidders to submit written questions to you in a specified period of time. Itis also recommended that all written questions and your responses be compiled and sent back to allbidders. This will provide consistency and fairness in the process.

The purpose of this meeting is to communicate to all bidders what you need and how you wantthem to respond.

Answering questions

In addition to the written responses from the bidder’s meeting, you will need to provide somemechanism for answering ad-hoc questions from bidders. The best way to do this is to require thatall questions be faxed or e-mailed to a specific person and provide a response within 24 hours. Itwould be impractical for your organization to provide these ad-hoc questions and answers to allbidders. It would be a good policy to take questions up to the submission date for proposals. Afterthat date no correspondence between a bidder and people involved with the selection processshould be allowed.

Deadline for submission

Establish a deadline for submission. All responses must be in by the specified time and thespecified location in order to be considered. Set you time to be a few hours before the close ofbusiness. Inevitably a bidder will get stuck in traffic or a courier will be delayed. This will giveyou a little cushion and allow you time to check in responses while still allowing you to go home ata reasonable time.

44 EVALUATION OF PROPOSALS

Evaluating proposals should be done by the RFP committee with all the members using the samecriteria as listed in the RFP. This process should be documented in case a protest arises. If youhave been specific defining your GIS needs and defining how bidders needed to respond, theevaluation process should be straight forward.

Sample Questions - Has the bidder:

• Proven they can meet all of the functionality needed?• Provided pricing that can be compared with other responses?• Described the types of services and support in an understandable way?• Provided references and related experience for you to check on?

Criteria for Evaluation

It is important that this process be documented in case a protest is submitted or to explain why aproposal was not accepted. Each of the criteria needs to be measurable or quantifiable.

Functional capabilitiesIn the Needs Assessment phase GIS functionality was identified and documented. Thisdocumentation of functionality should be defined in the RFP and used for this evaluation.Develop a checklist of the various functions and have each committee member fill out thechecklist for each proposal.

Vendor SupportWithout proper support any system is doomed to failure. Part of the evaluation is tounderstand the type of support being offered. What kind of response time is being offeredand what are the standards. Will the vendor provide answers to a problem within 24 hoursof a call? Will they provide on-site vs. factory service for hardware problem? Make sureyou are comfortable with the level of service being offered.

Cost / Maintenance FeeThere are a lot of ways to state the price of a proposal. It is recommended that you bespecific as possible in the RFP and bidder’s meeting about how the price should bestructured. The more pricing can be itemized in the proposal the easier it will be to comparethe responses to each other. A suggestion is to develop a pricing form for each bidder to fillout and include with their proposal. As a minimum have separate pricing for software,hardware, services and support. More detail for each of these sections would be nice, justdon’t get too carried away.

Interviews / Benchmark Test ( see Benchmark Test Guide)

After the RFP committee has evaluated the written proposals, a “short list” of bidders should beagreed upon. Any proposals that are not in compliance with the RFP or do not rank high in theevaluation should be eliminated from consideration the remaining bidders compromise the shortlist. Some marginally qualified bidders many need to be eliminated as well to keep the short list ofbidders a manageable size. These short list bidders will be invited to a interview and/or abenchmark.

During this process you will be evaluating the bidder on:

• Ability to interact with your organization• Technical ability• Ability to communicate effectively

Selecting a Proposal

Once the Interview / Benchmark is completed. The RFP committee members should compile all oftheir evaluations independently then meet as a group. This meeting should review all of theproposals and begin to focus on which proposal to select. At this meeting questions may arise thatneed to be answered in more detail. Take the time to get these answers from the bidder before aselection is made (generally a phone call will work but sometimes a follow up interview is neededif practical).

Once all of the committee’s questions are answered, it should move quickly to making a selectionand notifying the bidders. At this point a contract needs to be put in place that defines the scope ofwork outlined in the RFP. This contract needs to be executed before any further phase of GISimplementation is started.

55 GIS DELIVERY AND INSTALLATION PLAN

Once you have selected a vendor(s) for your system you will need to coordinate the delivery andset up of all of the components. there are many resources to call on to do this. The most obviousbeing the vendor. They should have demonstrated that they have some level of expertise with GISand can help you get up and running quickly. It is a good investment to buy their services to installand set up the system for you. These service can be contracted for on a time-and-material basis orunder a scope-of-service contract.

The most effective means of describing how to prepare the RFP is to do so by example. Theremainder of this guideline consists of selected parts from an actual RFP, - presented here toillustrate the scope, content, and level of detail needed. A properly prepared RFP increases thechances that the vendor responses will be most appropriate to the needs of the local government.

66 SAMPLE HARDWARE SPECIFICATIONS

Specifications for a system configuration to support Geographical Information System (GIS)development and operational applications follow. The system configuration consists of variousdevices that will be networked together to support data capture, storage, processing and display inboth digital and hard copy forms, including:

• mapping/analysis workstations (2)• color laser printer (1)• black and white laser printer (1)• cartridge tape drive (1)• color raster plotter (1)

The proposal shall include technical and functional capabilities of the devices offered to meet thesespecifications. Provision of the following information should be included for each device:

• manufacturer• model number• capabilities/configuration of each device in comparison to the device specifications• documentation provided with the device (i.e., manuals)• warranty included in the purchase price• the nature and duration of user support services included in the purchase price such as

maintenance agreements, user support and service, and the average time period betweenrequests for user support and on-sit technical service if available.

GIS Workstations

The Mapping/Analysis workstations will support a wide range of GIS activities, including databasedevelopment, database quality control, user application development, database maintenance and allGIS applications supported by fully functional GIS software such as cartographic production,geographic database queries, and advanced geographic analysis using both spatial and attributeinformation. One of the GIS workstations must support high capacity data storage, and multi-userGIS processing, and should perform all GIS operations and applications within acceptable userresponse times.

General Specifications for Workstations:

• Mass storage may be configured within the workstations' cabinetry and/or as externaldrives

• The workstations should be configured with a single high resolution (1280 x 1024 orgreater) color monitor with at least 19" minimum diagonal screen dimension

• All devices shall include a keyboard and a pointing device such as a mouse• Each GIS workstation should be network-ready, and should be capable of connecting

to a local area Ethernet network and supporting a minimum transmission speed of 10megabits per second (mbps).

• Multi-user, multi-tasking operating system supporting logical security measures such asuser name/password validation, and user access privileges.

• The devices should support virtual memory operations, either through a dedicatedhardware controllers(s) or through software (operating system) functions.

• Descriptions of options for upgrading speed and performance through the addition orreplacement of boards or other components in the existing cabinetry of the workstationsshould be provided.

Specific Details of Workstations:

Both workstations should support the following hardware specifications:

• The workstation should include a minimum of a 32-bit processor supporting both 64-bit address and data buses. The CPUs should operate at a minimum of 75 MHz clockspeed and/or have enough processing speed and capacity to support other intelligentGIS client devices. These will consist of X-Stations or PCs. The workstations mayhave multiple CPUs on board.

• The devices should include at least 128 MB (megabytes) of main memory and shallsupport 32 MB memory modules and be expandable to at least 256 MB.

• The devices should be configured with mass storage disk drive(s) for direct access ofdata and software functions. They will have a minimum of 3 GB of mass storage each

• The workstations will be configured with a quad speed CD-ROM drives that willfacilitate the installation of upgrades to the operating system, installation and upgrade ofapplication software, and user access and review of systems and applicationdocumentation.

• The devices should also be equipped with one 1.44 or 2.88 MB floppy drive each• The server must support multi-user/multi-tasking operations and must concurrently

support both server and host workstation functions.

• Vendors shall describe options for upgrading the speed and performance of the serverand mass storage capacity through the addition or replacement of boards or othercomponents in the existing cabinetry. Also, Vendors shall describe options forincreased performance and mass storage that involve connection of devices external tothe existing cabinetry.

Small-Format Color Printer

One (1) color printer will be used for the production of color hard copy graphic plots andnongraphic report generation.

The color laser printer should meet the specifications or equivalent described below:

• Minimum of 300 dots per inch (dpi) resolution• Minimum 100 sheet paper tray• Minimum of 4 MB memory onboard with capacity for memory upgrades• Support for letter, legal size, and 11"x17" paper sizes• Built-in postscript compatibility• Serial and parallel interface

Sample hard copy outputs from the proposed device(s) shall be included with the proposal.

Cartridge Tape Drive

The system should include one (1) 4mm DAT tape subsystem for the Planning and ZoningDepartment. The tape should have a capacity of not less than 5 GB. The tape subsystem willprovide a mechanism for performing system and data back-ups.

Large-Format Color Raster Plotter

A color raster plotter shall be included for the production of high quality, large format cartographicproducts. This device must provide a high-volume color plotting capacity. The plotter shallsupport 36" x 42" plots and produce color plots at a minimum resolution of 300 dots per. Theplotter shall be compatible with the proposed LAN hardware and communications protocols andmust be accessible by all workstations on the LAN. A sample hard copy output from the proposedplotter(s) shall be included in the proposal.

Additionally, the plotter shall meet the specifications described below:

• Capable of supporting true color plotting• Minimum of 8 MB memory onboard with capacity for memory upgrades• Support for all paper sizes, A through E size• Built-in postscript compatibility• Serial and parallel interface

Provide four (4) replacement paper rolls with the printer. The paper should be a high qualityglossy bond.

77 NETWORK AND COMMUNICATIONS SPECIFICATIONS

There is a requirement to connect new hardware in two departments. Existing software consists ofIntergraph's I-Dispatcher, emergency response dispatch system. Requirements for each level ofcommunications are outlined in the section below. Vendors shall state the level of compliance andprovide a description and cost quotation for all hardware and software components needed to meetthe requirements at each level of data communications. Vendors should include in the costproposal the cost of any specialized hardware devices that will be required to implement theproposed communication network.

Network Processing Requirements

Network processing requirements are as follows:

• Storage of data which is accessible by users on the network by specifying particularfiles, collections of features or attributes, and geographic areas

• Access security to allow assignment of different levels of access rights to portions ofthe GIS database by user name or physical device

• Ability to support query workstations on the network, directly connected to the server,or connected through remote communication lines so that network users can haveaccess to these devices and vice versa

• Ability to allow database queries directly from workstations on the network without theneed to download data to workstations

• Ability to allow network-wide access to plotters and printers, all with print/plot queriesfor generating hard copies

Network Management and Monitoring Capabilities

The proposed physical network should also be able to perform the following network managementfunctions:

• Access to data on remote nodes by reference to the node, disk, directory, and file• Access to programs on remote nodes by similar reference• Assignment of logical names or aliases for programs or data locations on remote nodes• Control of peripheral devices from any node on the network• Passing of mail messages across nodes• Program-to-program communications across nodes• Monitoring of traffic and errors on the network

The proposal shall include all cabling and devices required to implement all data communicationconnections, utilizing existing facilities.

Network Speed and Capacity

The proposed system must operate at a minimum raw data speed of 10 megabits per second. TheProposer shall provide information about the upper limit in numbers of mapping/analysis/queryworkstations that can be supported without major degradation in response time or error rates on theproposed network.

Transactions and Data Exchange with Existing Systems

Initially, the GIS network will not support on-line links with the existing IBM mainframe. Accessto data residing on the mainframe will be accomplished by downloading data onto 9-track tapes andthen re-writing this data onto current industry standard media such as 4mm data tapes or CDs.

88 SOFTWARE SPECIFICATIONS

Software Component Overview

The GIS software components shall fully support and exploit the capabilities of the proposedhardware platform and shall provide full functionality for entry, editing, maintenance, analysis,display, and hard copy output of both graphics and tabular data on a continuous and interactivebasis.

For purposes of this procurement, software component capabilities have been grouped into thefunctional categories of:

• Database structure• User interface• Data entry• Data editing/maintenance• Data query and analysis• Data display/output• Application development• Operating system requirements

Data Editing And Maintenance

The proposer shall describe the tools and capabilities of the proposed system to modify andmanipulate spatial and attribute data in the GIS for the following categories:

• Interactive Graphic Editing• Attribute Editing• File Copying• Deletion of Features• Edit Controls• Rubber Sheeting• Coordinate Registration and Transformations• Quality Control/Error Detection• Merging, Extraction, Edge Matching of Data• Data Transactions, including the capabilities of the proposed system to translate data

into and out of the following formats:

- GFIS to Proposed System Format (specify how attribute data is addressed- AutoCad DXF (specify how attribute data is addressed)- AutoCad CWG (specify how attribute data is addressed)- Intergraph IGDS (specify how attribute data is addressed)- USGS DLG and DEM- TIGER Line Files- ArcInfo Export Files- Exchange data with KVS Computer Assisted Mass Appraisal (CAMA) System

Data Query And Analysis

The proposed software shall support the following data query and analysis capabilities:

• Graphic Data Query• Area/Perimeter/Distance Calculation• Attribute Data Query• Spatial Aggregation• Buffer Analysis• Address Matching• Polygon Overlay Analysis• Linear Network Analysis• Area Districting and Zoning

Data Display/Output

The data display and output tool capabilities that the proposed software shall support including thefollowing:

• Graphic Display• Tabular Display• Raster Image Display/Production• Vector Map Overlay• Hard Copy Map Production• Hard Copy Report Production• Map Plot/Display Relationship with Scale• Graph/Chart Production• Interactive Map Composition

Application Development

The Proposer shall propose one of more software components that, in a well integrated manner,provide the following capabilities and features:

• Menu Design and Custom Application Development• Programming Features• Supporting High-Level (4 GL) Programming• Subroutine Libraries

Basic Operating System Requirements

The operating system component of the software shall be the primary operating system of theproposed hardware platform and shall provide all of the traditional features of current operatingsystems as described below:

• Multi-user Support• Multi-tasking, Multi-threading Support• Security Management• File Management• Memory Management• Database Backups• Error Monitoring/Disaster Recover• System Diagnostics• Anti-viral Protection• Electronic Mail (E-Mail)

Network Management Functions

The proposed system shall provide capabilities for monitoring and managing all data and deviceson the GIS network as one unified system and support the following capabilities:

• Multi-user Database Access and Maintenance• Monitoring of network Activity• Network Problem Diagnostics• Print and Plot Management

99 GIS DATABASE STRUCTURE

Database Model

A GIS database model defines the nature and usage of spatial (geographic)data with a database.The proposed software shall support a spatial data model that is capable of creating, managing, andmanipulating data sets, defined on the basis of spatial coordinates and associated attribute data sets.

Feature Types: The data model shall support multiple feature types including point,node, line, polygon, and text features

Data Storage: Features shall be stored as double precision x and y coordinates

Data Types: The data model shall support multiple graphic and nongraphic data types

Database Organization: Vendors shall describe strategies for organizing data intological groups on the basis of data themes, and shall describe the capabilities of the datamodel for supporting simple and complex feature types.

Topological Data Structures

The geographic data model shall support the creation and maintenance of topological data.Topology shall be created through execution of a software function to structure graphic data sets.Vendors shall describe the ability of the proposed data model to support logical polygons,networks, and user-defined topological structures.

Design

Software capabilities that support large-scale engineering and design activities should be outlinedas well as specific engineering functions and appropriate modules.

Raster Image Data

The Proposer shall describe support for storage of raster map images (e.g., scanned bluelines,orthophotos) and for raster scanned documents.

Continuous Geographic Database

The geographic data model shall support the creation and storage of a continuous geographicdatabase

Relational Database Management System

The Proposer shall recommend a relational database management system (RDBMS) that will beable to maintain a minimum of 30,000 records of parcel ownership information in a single tableand shall provide functionality for updating database content, queries, and production of reports.The recommended RDBMS must be either a part of the GIS software or have a direct accesscapability.

1 01 0 SUMMARY

The RFP sections presented above give a good example of the scope of topics and level of detailneeded. This particular RFP did not present a conceptual data model for consideration by thevenders, but rather specified general characteristics for the GIS data model required. An actualconceptual data model, rather than its general characteristics, could be more useful to vendors, andthus more productive for the user's organization.

GIS DEVELOPMENT GUIDE: GIS SYSTEM INTEGRATION

11 INTRODUCTION

At this point in the GIS development process the GIS hardware and software have been acquiredand data conversion is complete (or a substantial portion has been finished). Different componentsof the hardware and software may have been purchased separately. It is now necessary to put allthe pieces together, test them to make sure they work as expected, and to initiate all proceduresnecessary to use the GIS.

22 GIS SYSTEM COMPONENTS

GIS Software

Vendors will usually install and test their software. Acceptance criteria (often the performancemeasures used during the pilot study or benchmark test) will be needed and the vendors must meetthese criteria before you relieve them of their obligation to you. Check the functionality of theprogram(s) to ensure that you received what you expected. The vendor should fix any problemsthat arise, either in software functionality or performance prior to you indicating acceptance of thesoftware.

Check that not only the main GIS software works, but that it works in relation to the othersoftware programs that are part of your "total system," which also includes all legacy databases,software, and hardware. In addition to acceptable performance for each individual piece ofsoftware, make sure all software works together. Once the total system is your responsibility andproblems arise it can be very difficult to determine the part of the system causing the trouble.Although not nearly as common as in the past, the first response of a vendor can still be "blame theother guy!" Make the vendors responsible for providing you with one integrated system.Remember - they are the experts. Do not allow anything to be left up to you to check or test. Ifyou are uncomfortable about something or do not understand how something works, talk to thevendor representative and get an explanation. Additionally, technical support is an extremelyvaluable necessity. All contracts should include on-site technical support and then on-going phonesupport after the installation is complete.

GIS Hardware

Implementing your hardware system is about the same as your software and must occursimultaneously. Contract with the vendor to install and test the hardware components. As with thesoftware, choose acceptance criteria for the hardware and operating system. Check functionalityand performance of the hardware and have the vendor resolve any problems. Make sure thehardware is able to support the software, database, and network as required. Technical support,both on-site and telephone, should have been included in the contract with the hardware vendor.


Database

Integrating and testing hardware and software components are fairly well-defined processes andvendors have good experience with these tasks. However, dealing with larger and more complexdatabases has not been nearly as common in the GIS area. Therefore, adequate procedures andvendor experience may be lacking. There are two processes which remain basically userresponsibility:

• building a master database or library (database integration)

• integrating the database with the GIS hardware and software

Databaseintegration

Verifydelivery ofdata

Load tostaging area

Run QC routines orvisually verify

Determineerrors

Accept &run libraryloaderprogram

Check outdata to editingworkspace

Not acceptable

Contact vendor

Use edittools toupdate data

Notifycheckerwhen done

Use checkertools to verify

Accept & commit tolibrary

Check backto clean-uplibrary

Checkin masterlibrary

\

Errors?

Only a few?

Return to edit

No

Acceptablelevel

Fix bychecker

Figure 1 - Database Integration

Acquisition of Hardware and Software 3

Figure 1 illustrated the steps of building the master database from the converted data files (theproduct of the digitizing or scanning process). The overall process deals with quality controlchecking, other editing procedures, correction procedures, checking corrections for accuracy andfinally placing the data file into the master database (or library). It is assumed that organizing dataentities into logical groups (i.e., layers) has been defined during the previously completedlogical/physical database design activity. Processing to enter data into the master database mayinvolve restructuring the content of the digital/scanned files from data conversion into the finaldatabase structure, usually combining entities that may have been digitized separately.

Other database building processes that must be accomplished within the activities shown in figure 1are:

• linking GIS layers to attribute tables• edgematching between areas used in digitizing and repartitioning the spatial extent into

the final organization• initialization of all database related procedures needed for both establishing the database

and its continued maintenance

Procedural components needed to complete the database include those on the following list. Manyof these procedures will have been defined, at least initially, during database design and/or the pilotstudy and benchmark activities. The procedures are:

• naming convention for all files (covering versions, status, etc.)• definition of error conditions• definition of accuracy requirements• quality control routines• manual editing procedures• checking procedures (verification of corrections)• error recording (flags associated with data or other error/accuracy information recorded

in the database

Raw, digitizeddata files

Edited filesready forchecking

Completed(checked)files ready formaster database

Figure 2 - Library Structure to Support Editing


The second major process is the integration of the database and all other system components(figure 3).

EditingDeliveredData

Databasesystemintegration

SystemIntegration

Hardware

Software

Network

Figure 3 - System Integration

33 SYSTEM TESTING

Once the installations are complete, you need to test your integrated system. Test how the softwareprograms work together, how the network is running, are the computers running slowly whencomplex functions are requested or all workstations are running simultaneously, and if dataretrieval is quick enough, to name a few. This process should continue at least a week, if notmore. It is important to experiment with the system on multiple days, with different processesrunning, and with different numbers of people accessing the data. Ask your staff to document anyproblems and report these to the vendor. See that resolutions are provided back to you in a timelymanner. Utilize technical support lines and keep in mind that the vendors are responsible forfollowing through on what they told you would work.

44 USER TRAINING

Most hardware and software vendors offer classes to teach new users about their products. Youcan usually include vendor instruction as part of your contract with them. User groups often offerinformation sessions on software products where you can learn valuable information. Properinstruction is important, however, and is a step that should not be disregarded.


GIS DEVELOPMENT GUIDE: GIS APPLICATION DEVELOPMENT

11 INTRODUCTION

Through time, as users become more experienced with GIS, they require more complexapplications. The initial Needs Assessment will contain some applications of a complex nature,however the majority of initial applications will be straight-forward, using the basic functionalitythat is part of every commercial GIS (e.g., query, display). The more complex applicationsusually are not supported by the basic functions of a GIS but must be programmed using the GISmacro language or other programming language. This guideline identifies several categories ofapplications that must be prepared by users and how overall requirements change over time.

22 WHY APPLICATIONS ARE NEEDED

Sales brochures, live demos and journal articles touting the impressive and extensive array of GIScapabilities creates the impression that application development is a non-issue. The vendors, itwould seem, have already developed fully functional, out-of-the-box, meet-your-business-needs,GIS software. GIS can and should do anything and everything.

So why are we talking about application development?

Applications are the icing on the GIS layer cake; the highest level of customizable software. Theunderlying "cake" provides the functionality common to all user disciplines. Commercial GISpackages tend to focus on the common or basic applications - the "cake." When it comes tospecialized uses, application development fills the needs for functionality. Though there is a greatdeal of commonalty in the basic spatial query and display functions, there is still a need for otheradvanced applications. We need additional applications because needs are different betweenorganizations.

Commercial GIS development is driven by market pressure. The software vendors only respondto what makes economic sense for their market share. What's important to your organization maynot be important to others. Because of this, there are no truly "off-the-shelf" applications that willmatch all of your needs. You either have to adapt your uses to their data model and functionality oryou develop applications to fit your use environment.

33 CATEGORIES OF APPLICATIONS

Application development is not rewriting the GIS software, but instead custom applications to meetspecific needs. The applications may be as simple as a set of preferences that are stored for eachuser group or individual and are run as a macro at startup time. Or they may be a very complexquery that selects a group of layers, identifies features of interest based on attribute ranges, createsvariable width buffers, performs a series of overlays and produces a hard copy map. In eithercase, an application is required to convert the user's ideas into a usable, stable product.






Archives


GIS Database







Database Backups

Figure 1 - Life Cycle of a GIS Database


44 DATABASE APPLICATIONS

Applications are not restricted to user-defined needs. One of the short-comings of the needsassessment methodology presented earlier, is the focus on only end-user query, analysis, anddisplay requirements. Collective needs, particularly those related to system-wide functions, are notidentified by individual users. The most important of these are the data administration functionsfor maintaining the quality and integrity of the database, such as quality control, verification,editing, back-up routines, and security.

Database applications fall into the following categories:

• database set-up (described as part of GIS System Integration)• database management• database maintenance• data archiving and retention

Figure 1 again shows the database life-cycle. Each step identified in figure 1 needs to be fullydefined, as appropriate to the specifics of the GIS program. The main point here is not how thesesteps are completed but rather to identify all of the necessary steps and to emphasize the importanceof planning and executing each one.

The MSAccess™ metadata software tool accompanying these guides sets forth a structure forcreating documentation needed for the management and maintenance of the GIS database. Tabledefinitions for the metadata tool are in the appendix to the GIS use and Maintenance Guideline.

Formal Specifications for Advanced Applications

The documentation of applications is the Needs Assessment guideline describes methods suitablefor preparing full and formal specifications for all applications. However, most applications in anew GIS will be of the simpler, more basic type (display, query, map overlay). These applicationswill likely be satisfied by the normal functionality that is included in most commercial GIS.

More complex applications, either database or spatial analysis, will require development using theGIS macro programming language. For these applications the process of preparing formalspecifications, similar to what any large programming project uses, should be followed. Thetechniques recommended in the Needs Assessment guideline are data modeling by application (E-Rtechnique) and data flow diagramming. These techniques are suitable to provide an overview of acomplex application. Additional techniques should be used, as appropriate, including:

• structural analysis and programming• rapid prototyping

As the application development needs increase, there will be a need for additional staff with theappropriate programming skills and experience using the macro programming language of the GIS.


GIS DEVELOPMENT GUIDE: GIS USE AND MAINTENANCE

11 INTRODUCTION

The last step in GIS implementation is to put the system to use. With system integration andtesting complete and at least some applications available for use, the system can be released tousers. Two broad categories of activity must be in place at this time:

• user support and service

• system maintenance (database, hardware, software)

While we are describing the activities here, it should be noted that most of what is recommended inthis final guideline should have been defined during the detailed database designstep. So, if you are reading these documents for the first time and have yet to begin an in-depthsystem planning activity, you should add everything that follows to the Database Planning andDesign and Pilot Study/Benchmark steps.

One final comment - usually substantial time passes between the initiation of the needs assessmentand the time a GIS is ready to use. A lot will change during this time period. The GIS designactivity is in itself a change agent - users will understand more about a GIS and its associatedtechnology after the needs assessment is concluded and will consequently expect more. Theapplications originally identified, plus all subsequent derived information, will change; theavailable GIS hardware and software will change; and the underlying computer technology willchange. So basically, while you the GIS designer is trying to come to a set of definitive decisionsto implement the GIS, everything is constantly changing. The best you will be able to do is tomonitor all areas of possible change, at best a difficult task, and to decide on the GIS with theknowledge that the maintenance phase will have to accomodate substantial change. Any and allprocedures we have discussed as "maintenance" in these guidelines will need to be put in placeimmediately after the corresponding document is created or decision is made.

22 USER SUPPORT AND SERVICE

User support falls into the following categories:

• basic orientation in GIS is preparation for the needs assessment

• continued briefings during the planning, design, and implementation phases

• user training courses as needed in computing, general purpose software, databases,GIS, and spatial analysis

• user involvement and evaluation during pilot study and benchmark tests

• user training in specific application use


• technical support service while GIS is in use

• user feedback procedure to identify system enhancements - GIS functions/applicationsand database

• data error/problem reporting and resolution procedures

• user feedback on data accuracy and system performance

• user involvement in decisions on all system upgrades - data, software, and hardware

It is difficult to identify which of the above is most important. This will vary by situation and overtime. However, the first main point in user dissatisfaction comes with the time period between theneeds assessment, where expectations are raised, and the first operational use of the system. Thisuser dissatisfaction can be such that there is a temptation to develop quick-and-easy applications forearly use, to take short-cuts in database development, or to extend a pilot study into actual use.Such a situation cannot always be avoided, however any premature use of this type will likely leadto more user dissatisfaction in the long term.

GIS System and Database Maintenance

The structure of this task is shown in figure 1. Three driving components of maintenance andchange are: system enhancements, database expansion, and routine system maintenance (updates).Figure 1 indicates the type of change that may occur in each component and identifies the benefitsand costs associated with the on-going GIS maintenance activity. As users can be negativelyaffected by charges, major enhancements or expansions need to be subjected to user review, evenif the change is only internal to the GIS and on the surface would not affect users.

33 DATA MAINTENACE PROCEDURES

Managing Existing Data

Backup / Restore

A reliable backup system is necessary for any database. Should anything happen to your hardware(i.e. the file server disk drive crashes), you will be able to restore your backup data to anothermachine and be operational again in minutes without losing the database. Determine a schedule forregular backups of the system. This can be done daily, weekly, or monthly depending on the sizeof the database and amount of changes being made to it. If your staff only makes edits once aweek, a weekly backup should be enough. However, if changes are constantly being made, adaily backup is important. If you have a large dataset that would be time consuming to backupevery day, consider backing up only part of the database daily and then do a full backup once perweek.


GIS and Database

System EnhancementRequests

(Committee Review)

Database Expansion(Committee Review)

Routine SystemMaintenance

•Additional Functionality•Hardware and Software •Upgrades•New Technology (GPS)•Interface with Additional•Systems

•Additional Attributes•New Entities•Expanded Spatial Extent

•Problem/Error•Resolution (Bug Fixes)•Database Updating

Benefits

•User satifications (GIS can do more)•Additional sharing (data and other)•Improved performance

Costs

•Dollar cost of enhancement•GIS staff retraining•More for GIS staff to manage & maintain•User retraining•System down-time

Figure 1 - Overview of GIS Maintenance


Granting Access To Data

Often times GIS applications call for users to display and/or analyze the data only, without editingit. By granting read only access to the data to these types of users, you eliminate any chances fordata to be deleted or otherwise altered. If you have other users who edit data, such as supervisorsor trained technicians, grant them read and write permissions to the data. Data access can usuallybe handled by the GIS application, by the database software, and/or by network (if you arerunning one) software security operations.

Another important function in data maintenance to consider is transaction maintenance. This typeof application registers items in the database such as when a record was updated, by whom, andfrom what source the changes came from. A history log is kept on each record and old recordsbeing updated can be sent to an archive file. This step may seem unnecessary in the beginning, butas the database enlarges an application such as this will be of great value. If there are problems orquestions with data, you will know exactly who to turn to to question its accuracy and quality.

Records Management And Retention

Four important questions should be looked at with regards to management and retention: what tokeep, how long to keep it, how to keep it, and how often to keep it. The New York State Archivesand Records Administration is currently developing additional guidelines to regulate and definerecords management and retention policies for GIS in local government. Until these guidelines arecompleted, please see the “Local Government Records Technical Information Series No. 39”pamphlet for more assistance. A record in a GIS is difficult to define. It can include: data in thedatabase, maps, aerial photographs, data dictionaries, and metadata. To help determine how longto keep your data, obtain a retention schedule from SARA. These are used for hardcopy dataretention but can be modified and used for your purposes. Electronic media is generally used fordata storage. Again, SARA is developing regulations on this, so it would be best to contact themfor guidance.

Reviewing Current Data For Potential Errors and Changes

Develop a system for QC of the data. Most likely the dataset will be too large to be able to checkeverything. Determine what will be checked and what degree of accuracy you require. Severalthings you should look for are described below.

Incompleteness

Begin by checking to make sure all the layers of data that should be in the database are there. Also,make sure no layers are repeated. Define a process for checking some of the individual features ofeach layer. Determine if there is any missing data and make sure data is not repeated in more thanone layer.


Errors

There are two types of errors you should be concerned with: positional and attribute. Positionalerrors are defined as absolute or relative. “Relative accuracy is a measure of the maximumdeviation between the interval between two objects on a map and the corresponding intervalbetween the actual objects in the field. For example, a measurement on a map from a water valveto the street centerline must be within a certain relative accuracy requirement to be accepted.Relative accuracy does not relate to a reference grid and the correct geographic position of theobject is not relevant. Absolute accuracy is a measure of the maximum deviation between thelocation where a feature is shown on the map and its true location on the surface of the earth(Montgomery and Schuch, 132-133).” Attribute errors are problems with the feature itself, notwhere it is located.

Topological Errors

Many GIS software packages are equipped to find topological errors in your dataset. Use availabletools, or develop your own, to detect the following types of errors: closure (unclosed polygons),connectivity (unconnected arcs that should be connected), and coincident features. Coincidentfeatures (shared arcs) are difficult to locate; they may appear to have one arc between two features,but it turns out to be two arcs, one on top of the other. This should be corrected because it canresult in sliver polygons (small gaps between two polygons).

Detecting Change and Identifying Sources for Updates

As a local government several internal sources for data updates would include: building permitsissued, real estate transactions, subdivisions proposed and/or approved by the town council, andzoning changes. This is all important information you might want to include in your GIS.External sources of data updates might include: aerial photo surveys, subdivision contractordrawings, the Department of Transportation, the U.S. Postal Service, the Office of Real PropertyServices, and state and federal agencies (i.e. environmental groups, soil surveys, and the CoastGuard).

Collection of New Information

Once you have determined that there are new pieces of information you want to capture in yourGIS, you must decide how you will collect it. Data conversion can be expensive; however, youknow what the accuracy and quality of the data will be and you will get the information when youwant it. Many of the sources listed in the above section will have digital data they would be willingto sell. Consider signing a contract to receive any updates they make. A third option for datacollection is finding a way to work it into the staff’s daily routine. This makes data collection takelonger, but it does not disrupt workflow and it costs less. Determine what field crew or staffwould be able to capture the data without it being a burden on their job and decide which peopleknow the most about the data you are attempting to capture.


Applying the Edits and Tracking Changes

Editing the database can become a tedious task. However, it is important to the data integrity thatthe edits are done accurately and consistently. All changes should be tracked in a way, asdescribed above, that will allow you to determine when the records were updated, by whom, andwhat level of confidence the data was rated. When necessary, a history log can be displayed foreach record and all changes to the data will be noted. Archiving data is a good way to keep out-of-date information from cluttering the system, while allowing easy recall should there be somethingwrong with the updates or new data.

Verifying the Corrections

Develop a QC process or use the procedure you’ve already implemented to check the correctionsmade. You will not want to verify every change made, but you could select a random number ofrecords and confirm that corrections were made correctly.

Updating the Master Database

Once edits are made and you’ve verified that they were updated correctly in the database the masterdatabase can be updated. If edits are being made on a daily basis, the master database may beupdated on a daily basis as well, but be sure not to skip the correction verifying step.

Distributing the Updates to Users

This will depend on the technology being used. Some users will have access to a modem and candial-up and download any edits you make. Other users will have to receive the data on a tape ordisk. Determine a schedule and plan for distributing edits to your users that best suits yourcompany.

Montgomery, Glenn E. and Harold C. Schuch, GIS Data Conversion Handbook, GIS World, Inc.and UGC Consulting, Fort Collins, 1993.


Appendix A


OrganizationInfo

Name of organization/agency:

Department:

Room/Suite #:

Number and Street Name:

City:

State:

Zip Code:

Phone Number:

Fax Number:

Contact Person:

Phone Number/Extension:

Email Address:

Organization Internet Address:

Comments:

CONTINUE InputingFor This

Organization

Town of Amherst

Assessor

5525 Main Street

Amherst

NY

(716)555-8888 x777

John Henry

(716)555-7444

(716)555-8888

14221-

[email protected]

[email protected]

Input NEXTOrganization

EXIT Database


ReferenceInfo

Organization:

Filename:

File Format:

Availability:

Cost:

File Internet Address:

Metadata Created By:

Date Metadata Created:

Metadata Updated By:

Date Metadata Updated:

Metadata Standard Name:

Comments:

CONTINUE Inputing For This

File

Town of Amherst

ParcelMap

ARC/INFO

yes

$15.00

ftp.assr.amh.gov/pub

New York State Local Government Standard

15-Feb-96

Laura Hiffel

07-May-95

Lee Stockholm

Input NEXT FileSAVE and Input

NextOrganization


DataObjectInfo

Data Object Name:

Type:

Data Object Description:

Spatial Object Type:

Comments:

CONTINUE withSpatial Info

Parcel

Simple

Land ownership parcel

Polygon

CONTINUE withAttribute Info

CONTINUE withLineage Info

CONTINUE withUpdate Info

Input NEXT DataObject

EXIT DataObject Info


SpatialObjectInfoData Object Name:


Place Name:

Projection Name/Description:

HCS Name:

HCS Datum:

HCS X-offset:

HCS Y-offset:

HCS Xmin:

HCS Xmax:

HCS Ymin:

HCS Ymax:

HCS Units:

HCS Accuracy Description:

VCS Name:

VCS Datum:

VCS Zmin:

VCS Zmax:

VCS Units:

VCS Accuracy Description:

Comments:

CONTINUE withSource

Document

Parcel

Polygon

Amherst

UTM

State plane Coordinate System

NAD83

42

83

25

800000

1000000

98

GO BACK toData Object

Form

Feet

National Map Accuracy Standard

0

0


SourceDocumentInfo

Data Object Name:


Source DocumentName:

Type:

Scale:

Date Document Created:

Date Last Updated:

Date Digitized/Scanned:

Digitizing/Scanning Method Description:

Accuracy Description:

Comments:

Parcel

Polygon

Parcel Map

Map

Variable: 1" = 50 feet to 1" = 200 feet


Form

17-Nov-89

05-Oct-94

24-Apr-95

Manual digitized with Wilde B8

90% of all tested points within 2 feet


AttributeInfo

Data Object Name:

Data Attribute Name:

Attribute Description:

Attribute Filename:

Codeset Name/Description:

Measurement Units:


Comments:

CONTINUE withData Dictionary

Parcel

SBL Number

Section, Block, and Lot Number

Parcel,PAT

N/A


Form

N/A

N/A


DataDictionaryInfo

Data Object Name:

Data Attribute Name:

Data Type:

Field Length:

Required:

Comments:

Parcel

SBL Number

Character

15

Yes


Form


Lineage

Data Object Name:

Data Object1:

Data Object2:

Description of Spatial Operation and Parameters:


Comments:

Parcel

N/A

N/A

N/A

N/A


Form


UpdateInfo

Data Object Name:

Update Frequency:

Date:

Updated By:

Comments:

Parcel

Annual

01-Jan-96

Lee Stockholm

CONTINUE withArchive Info


Form


ArchiveInfo

Data Object Name:

Retention Class:

Retention Period:

Date Archived:

Archived By:

Date to be Destroyed:

Parcel

A

Permanent

31-Dec-95

Lee Stockholm


Form

Date post:	08-Nov-2014
Category:	Documents
Upload:	javier-valencia
View:	45 times
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