Ref: Geographic Information System and Science, www.gis.com, www.wiley.co.uk/gis, www.wiley.com/gis

By Hoeung Rathsokha, MSCIM

GIS and Remote SensingGIS and Remote Sensing

WHAT IS GIS? WHAT IS GIS?

NORTON UNIVERSITYCollege of Sciences

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What is GIS?

Geographic Information System (GIS) is defined as an information system that is used to input, store, retrieve, manipulate, analyze and output geographically referenced data or geospatial data, in order to support decision making for planning and management of land use, natural resources, environment, transportation, urban facilities, and other administrative records.

1. Definition of GIS

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What is GIS? (cont.)

2. key components of GIS

ComputerComputerSystemSystem

GeospatialGeospatialDataData UserUser

-Hardware -Software- Procedure

-Updating-Analysis-Implementation

Graphic orGraphic orgeometricgeometric DataData

Thematic orThematic orAttribute dataAttribute data

Vector Raster represent geometry of topology, size, shape, position and orientation Point/node

Line/arcArea/polygon

represent textual data

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Spatial Representation (raster data)

At what spatial resolution do we represent the World?What are potential implications of this choice?

building lake river woodland

Real World Low spatial resolutionHigher spatial resolution

What is GIS? (cont.)

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Spatial Representation (vector data)The vector data model represents each feature as a row in a table, and feature shapes are defined by x, y locations in space (the GIS connects the dots to draw lines and outlines). Features can be discrete locations or events, lines, or polygons.

Real World Low spatial resolutionHigher spatial resolution

What is GIS? (cont.)

This electric utility map uses points, lines, and polygons to represent buildings, streets, and electrical facilities

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What is GIS? (cont.)

Once a GIS is implemented, the following benefits are expected:Geospatial data are better maintained in a standard format.Revision and updating are easier.Geospatial data and information are easier to search, analyze and represent.Geospatial data can be shared and exchanged freely.

3. The Benefit of GIS

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What is GIS? (cont.)

Time and money are saved.

better decisions can be made

3. The Benefit of GIS

Shows a comparison between geospatial information management with and without GIS

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Information Collection

Primary Geographic Data Capture: use in GIS by direct measurements of objects. Both RASTER and VECTOR data capture methods are available.

Secondary Geographic Data Capture: the process of creating raster and vector files and databases from maps and other hardcopy documents.

Data Collection

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Vector Data

Total station together with GPS (Global Positioning System) will modernize the ground survey. It is very accurate but too expensive to cover wide areas.

Ground survey with GPS

We’re already known a network of satellites, monitoring stations, and inexpensive receivers used for primary GIS data capture. GPS is a collection of 27 NAVSTAR satellites orbiting the Earth at a height of 12 500 miles (20 116.8 km), five monitoring stations, and individual receivers. The GPS was originally funded by the US Department of defense, and for many years military users had access to only the most accurately data.

Fortunately this selective availability was removed in May 2000 so that now civilian and military users can fix the X, Y, Z location of objects relatively easily to an accuracy of better than 10m with standard equipment.

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Vector Data

GPS measurement to capture center roads (Tract),

1. Survey measurement with GPS

The opened job with Mobile-Mapper

LineLine SurfaceSurfaceGPS deviceGPS device

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Vector Data

and the survey point locations.

1. Survey measurement with GPS

The opened job with Mobile-Mapper

GPS deviceGPS device

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Vector Data

With Total Station in the field – for capture Points data of the land or house plan demarcation.

2. Survey measurement with Total Station

φ

LEICA TC600

Pt-1

Pt-2

Pt-3

Pt-2

Building

Total Station measurement

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Vector Data

Used scanner to capture raster data and load it in a GIS application by register the raster map so that the map will have geographic coordinates and then digitizing for vector data.

3. Digitize measurement with Scanner

MAPIn

hardcopy

RASTERDATA

VECTORDATA

Create Load + Reg. Coor. Sys.& convert to

Process flow of digitize measurement

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Tablet digitizers with a free cursor connected with a personal computer are the most common device for digitizing spatial features with the plane-metric coordinates from analog maps. The analog map is placed on the surface of the digitizing tablet as shown in Figure. The size of digitizer usually ranges from A3 to A0 size.

Typical Errors

4. Digitizers for Vector Data Input

Vector Data

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Vector Data

With DXF or SHP file formatter can be Import/export data to, and reverse process

Dxf file format from autoCAD application, from MapSource application or from Total Station device are directed import to.

Another way, allow import Dbase DBF, Excel XLS, Access Database MDB, and Delimited ASCII txt files.

5. Data Transferring

Note: The Universal Translator allows you to import and export MapInfo data to and from other popular mapping file formats.