Geographical Information System LITERATURE REVIEW

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2.4 Geographical Information System

Geographic Information System GIS is a computer-based system used to store and manipulate geographic information. It is designed for collection, storage, and analysis of objects and phenomena where geographic location is an important characteristic or critical to the analysis Aronoff, 1991. 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. A computer system for GIS consists of hardware, software and procedure designed to support the data capture, processing, analysis, modeling and display of geospatial data Murai, 1996. Geographic information can be represented with geometric information such as location, shape and distribution, and attribute information such as characteristics and nature. Vectors and raster forms are the major representation models for geometric information. Most objects on a map can be represented as a combination of a point or node, edge or arc and area or polygon, which are vector forms. A point is represented by geographic coordinates. An edge is represented by a series of line segments with a start point and an end point. A polygon is defined as the sequential edges of a boundary. The inter-relationship between points, edges, and areas is called a topological relationship. In the raster form, the object space is divided into a group of regularly spaced grids pixels to which the attributes are assigned. The raster form is basically identical to the data format of remote sensing data Jars, 1993. GIS can be a very important tool in decision making for sustainable development, because GIS can provide decision makers with useful information by means of analysis and assessment of spatial database. Decision making including policy making, planning and management can be interactively implemented taking into consideration human driving forces through public. 15 Driving forces include population growth, health and wealth, technology, politics, economics etc. by which human society will set up targets and goals on how to improve the quality of life Bregt, 1997.

2.5 Multi Criteria Decision Analysis MCDA