USING THE G.I.S. INSTRUMENTS TO OPTIMIZE THE DECISIONAL PROCESS AT THE LOCAL COMUNITIES LEVEL

Mihai Valentin Herbei – Ph. D. Eng., University of Agricol Sciences and Veterinary Medicine of Banat Timisoara – Faculty of Agronomy Ular Roxana - Univ. assist. Ph. D. student, Eng. University of Petrosani, Faculty of Mine

ABSTRACT: "Every object present on the Earth can be geo-referenced", is the fundamental key of associating any database to G.I.S. Here, term 'database' is a collection of information about things and their relationship to each other, and 'geo-referencing' refers to the location of a layer or coverage in space defined by the co-ordinate referencing system. G.I.S. is a system of hardware and software used for storage, retrieval, mapping, and analysis of geographic data.  Practitioners also regard the total G.I.S. as including the operating personnel and the data that go into the system.  Spatial features are stored in a coordinate system (latitude/longitude, state plane, UTM, etc.), which references a particular place on the earth.  Descriptive attributes in tabular form are associated with spatial features.  Spatial data and associated attributes in the same coordinate system can then be layered together for mapping and analysis .G.I.S. can be used for scientific investigations, resource management, and development planning.

1. Introduction

G.I.S. differs from CAD and other graphical computer applications in that all spatial data is geographically referenced to a map projection in an earth coordinate system.  For the most part, spatial data can be "re-projected" from one coordinate system into another, thus data from various sources can be brought together into a common database and integrated using G.I.S. software.  Boundaries of spatial features should "register" or align properly when re-projected into the same coordinate system. Another property of a G.I.S. database is that it has "topology," which defines the spatial relationships between features.  The fundamental components of spatial data in a G.I.S. are points, lines (arcs), and polygons.  When topological relationships exist, you can perform analyses, such as modeling the flow through connecting lines in a network, combining adjacent polygons that have similar characteristics, and overlaying geographic feature. The main purpose for introducing the G.I.S. technology consists in increasing the efficient possibilities for maintaining and updating the data. In the narrow sense, a G.I.S. consists of a system for data input in vector form, in raster form and in alphanumeric form, a CPU containing the programs for data processing, data storage and data analysis and of facilities for visualization and hard copy output of the data. In a broad sense, a G.I.S. includes the data, which are managed by an administration or a unit conducting a project for the purposes of data inventory, data analysis

and data presentation for administrative support or for decision support. (Fig. 1. and 2).

Fig. 1 The sketch of G.I.S.

Fig.2 Concept of a G.I.S.

2. Structure of a G.I.S. application

The G.I.S. technology is used in all fields for which the spatial information is relevant, that means in all fields that use the geographical map for stocking, analyzing and representing the data which are processed.

No matter what is the field, any G.I.S. application includes a spatial data base (a digital map) and a soft which exploit these data bases.

The digital map must contain the spatial data specific to any field whose it is designated to this application. In order to furnish some useful information, this data base must be actual, which means it must represent correctly the terrain (geographic space) that is always under changing.

This exploitation soft is made from many functions of analyzing the spatial data contained into the digital map and of visualizing the resulted information, specific to the application field.

3. Accomplishing the digital map

The digital map must be made by vaporizing all the existent resources based on a good analyze of these content and the involved costs, following to assure the

necessary quality, in conditions of maxim efficiency. Into the fig. 3 it is presented a general scheme of principle of sources that can be taken into consideration for making the digital map.

Acquisitioning the data is the process of conversion of the data for the shape in which it is exists in one that can be used by a G.I.S.

The first aspect we may take into account here is the map precision standard of 0,2 mm that depends on the scale assures the G.I.S. data to have a precession like into the following table:

Table 1CARTOGRAPHIC

ACCURACYCLASSIC

MAP SCALE

ACCURACY OF G.I.S.

DATA

0,2 mm

1: 25000 5 m

1: 10000 2 m

1: 5000 1 m

1: 2000 0,4 m

1: 1000 0,2 m

1: 500 0,1 m

In order that the spatial data can be obtained from a great variety of sources, it must be done the difference between acquisitioning new data and of the existent one.

Each data source presumes the existence of some special programs that are used for transforming the data into a shape of the digital map.

Fig. 3 Data sources for G.I.S.

4. Models of data from the digital map

There are two important components of geographic data: its geographic position and its attributes or properties. In other words, spatial data (where is it?) and attribute data (what is it?). Geographic position specifies the location of a feature or phenomena by using a certain coordinate system. The attributes refer to the properties of spatial entities such as identity (e.g., maize, granite, lake), ordinal (ranking, e.g., class 1, class 2, class 3, and so on), or scalar (value, e.g., water depth, elevation, erosion rate, and so on). They are often referred to as non-spatial data since they do not in themselves represent location information.

Spatial features in a G.I.S. database are stored in either vector or raster form. G.I.S. data structures adhering to a "vector" format store the position of map features as pairs of x, y (and sometimes z) coordinates. A point is described by a single X-Y coordinate pair and by its name or label. A line is described by a set of co-ordinate pairs and by its name or label. In reality, a line is described by an infinite number of points. In practice, this is not a feasible way of storing a line. Therefore, a line is built up of straight line segments. An area, also called a polygon, is described by a set of coordinate pairs and by its name or label, with the difference that the coordinate pairs at the beginning and the end are the same (Fig. 4,5).

Fig. 4 Point, line and area objects

 Fig. 5 Vector format

A vector format represents the location and shape of features and boundaries precisely. Only the accuracy and scale of the map compilation process; the resolution of input devices; and the skill of the operator inputting data limit the precision.

In contrast, the "raster" or "grid-based" format generalizes map features as cells or pixels in a grid matrix (Fig. 6). The space is defined by a matrix of points or cells, organized into rows and columns. If the rows and columns are numbered, the position of each element can be specified by using column number and row number, which can be linked to coordinate positions through the introduction of a coordinate system. Each cell has a attribute value (a number) that represent a geographic phenomenon or nominal data such as land-use class, rainfall or elevation. The fineness of the grid or, in other words, the size of the cells in the grid matrix, will determine the level of detail at which map features are represented. There are advantages to the raster format for storing and processing some types of data in G.I.S..

Fig. 6 Raster format

The "raster" or "grid-based" format generalizes map features as cells or pixels in a grid matrix (Fig. 7).

FigFig. 7 Vector-raster relationship

The vector or the raster data are also linked (Fig. 8) to non-graphic information specifying place names and object numbers, which in databases may further be linked to a great variety of coded or alphanumerical attributes (e.g. owners of a parcel, inhabitants of a house, characteristics of a utility feature, statistical data for a defined area).

Fig. 8 Attribute links

In both models the geographic data of a certain territory are organized on many layers or thematic coverage (Fig. 9.).

The digital map is a special territory is represented by the sum of all layers that have been defines. A derived map will be constituted from a layer or a certain combination of layers from the existent ones.

One of the main problems that should be solved inside the project of informatics system will be to define the layers that form the digital map and to establish the entities that belong to each layer.

Fig. 9 Layers in a Digital Map

5. Spatial analyses

The most important feature of a G.I.S. consists in its capacity to make spatial analyses, which means to process the spatial data (geographical data) with the purpose to obtain information (reports) regarding the studied area. With this feature of spatial analyze is different the software dedicated to G.I.S. over the software like the CAD. The processing of spatial data is made based on some algorithms specific by using own operations for these such data.

A geographic information system must include some facilities for answering to the following 5 general questions:

LOCATION: "What is at….?"The first of these questions seeks to find what exists at a particular location. A location can be described in many ways, using, for example, place name, postcode, or geographic reference such as longitude/ latitude or x and y.

CONDITION "Where is it..?"The second question is the converse of the first and requires spatial data to answer. Instead of identifying what exists at a given location, one may wish to find locations where certain conditions are satisfied (e.g., a non-forest area of at least 2,000 square meters in size, within 100 meters of a road, and with soils suitable for supporting buildings).

TRENDS: "What has changed since./.?"The third question might involve both of the first two and seeks to find the differences within an area over time, for example, changes in forest cover or the extent of urbanization over the last ten years.

PATTERNS: "What spatial pattern exists...?”This question is more sophisticated. One might ask this question to determine whether landslides are mostly occurring near streams, or to find out which are the traffic points where the accidents occur more frequently. It might be just as important to know how many anomalies there are that do not fit the pattern and where they are located.

MODELLING: "What IF...?""What if…" questions are posed to determine what happens, for example, if a new road is added to a network or if a toxic substance seeps into the local groundwater supply. Answering this type of question

requires both geographic and other information (as well as specific models).

The main spatial operations are as follows: Operations on a single layer; Operations on multiple layers; Statistic analyze; Network analyze; Analyze of the surfaces – making the digital model of the terrain.

6. Examples of spatial analyses

6.1. Operations on a single layer

These operations are called also operations on the horizontal. For the vectorial maps it is necessary that the layers should contain only the graphic primitives of same type, so it will be used the group of operations on many layers.

These operations on the horizontal are as follows: the manipulation of the graphic primitives (operations over the contours and analyze of proximity), their selection (their identification) and their classification (grouping the graphic primitives in classes in order to make a statistic analyze).

The operations that are made over the contours are as follows: selecting a part of the layer (CLIP – coping a part of a coverage), removing some graphic primitives (ERASE), creating some subdivisions (SPLIT), assembling some adjacent maps (MAPJOIN), removing the limits that separate the polygons of same type (DISOLVE) and eliminating some lines (ELIMINATE).

The analyze of proximity represents the identification some contours at equal distance to graphic primitive (BUFFER)(Fig. 10).

Fig.10 Diagram of simple buffers and a setback

Fig. 11 Geometric spatial queries

6.2. Operations on multiple layers

In order to accomplish the operations on multiple layers is needed that all maps involved in this process should be at the same scale and should have the same system of coordinates.

These operations are called operations on vertical and they are based on the relations between data on different layers. So, a complex layer may be dissolved in thematic layers and many layers may be combined. These operations are of type “overlay”, proximity analyze and analyze of spatial correlations.

The overlay analyzes (Fig. 10) creates some combinations between graphic primitives on different layers and built links between data based on some logical conditions imposed of type: AND, OR, XOR, NOT (negation).

These operations are as follows: UNION and INTERSECT (intersection). UNION makes that two or many layers should overlap and should result a new coverage. It uses the logic operator OR and it does not that the layers should contain the same type of graphic primitives. INTERSECT uses the logic operator AND, the result being a coverage that contains the common part from the layer and data from the second layer. In this situation the layers must be at the same type of graphic primitive.

This operation is more used on layers that contain only polygons.

Fig.12 Example of Polygon-overlay analyze

Fig.13 Example of Raster-overlay analyze

6.3. Generating and interpreting the digital model of the terrain

Fig. 14 The 3D model of the surface

Fig.15 Example of map of Slope

7. Conclusions

A geographic information system is an information management tool that helps us to store, organize and utilize spatial information in a form that will enable everyday tasks to be completed more efficiently. Since its rapid growth over the last two decades, G.I.S. technology has become a vital element for us to maintain and integrate information. G.I.S. software, and the hardware required to operate it, have become much more affordable and easy to use. This has resulted in the ability to develop a G.I.S. without making large investments in software, hardware and the support staff that were once needed to implement it. With the implementations of G.I.S., we will see dramatic improvements in the way we access information,

execute responsibilities, and respond to request from citizens, potential developers and other clients. 

To accomplish the digital maps and to introduce the G.I.S. systems into local community sectors will increase the level and quality of their decisional process. Being very used in different fields, and starting from the information necessary to any citizen and till environment protection, from the marketing strategies to resources administration, the G.I.S. marked a revolution in solving the problems. The quality information means quality decisions. And G.I.S. offers this possibility, transforming some simple information in real information and offering the interactive access to them.

8. References

1. DUMITRU, G. „Geographic Information System”, Ed. Albastra, 20012. HERBEI M. - “Performing a Geographic Information System into the areas affected by the mining exploitations by using modern techniques and technologies” - Doctorate thesis, Petrosani, 2009 3. HERBEI O., HERBEI M. – “Geographic Information Systems. Theoretical and applications”, Ed. Universitas, Petroşani, 4. KONECNY, G. – “Geoinformation”, London, 2003