GEOGRAPHICAL INFORMATION SYSTEM (GIS)

Geographical Information Systems – Overview -- GIS have been defined as ‘automated systems for the capture, storage, retrieval, analysis, and display of spatial data’ (Clarke, 1995,p13). GIS can be used for any area or application that depends largely on geographic data ie. data that is geographically referenced or is ‘mappable’. As the scope is quite wide it is not surprising that there are many definitions as well as many acronyms (LIS, NRIS, AM/FM etc) which cover the field referred to as GIS related technologies .
Geographical Information Systems – Overview -- GIS has its origins in Geography, Cartography, Surveying and Computer Science – disciplines which deal with various aspects of geography and the associated geographic data. Its rapid development and widespread adoption over the past decade has been influenced very strongly by developments in computing in general eg. higher performance, lower cost, easier to use hardware and software and the continuous enhancement of the application capabilities of software
Over time GIS applications have become more sophisticated – changing from earlier static inventory type applications (basically, electronic versions of atlases or manual procedures) to current real time decision-support type management applications.

Topic structure
• GIS defined
• GIS applications
• GIS development
• GIS components
• Sources of information on GIS

General Definition
“A system of hardware, software, data, people, organisations and institutional arrangements for collecting, storing, analysing and disseminating information about areas of the earth (Dueker & Kjerne 1989:7-8

Definition Of Gis
“The organized activity by which people:
• Measure aspects of geographic phenomena and processes
• Represent these measurements, usually in the form of a computer database, to emphasize spatial themes, entities and relationships
• Operate upon these representations to produce more measurements and to discover new relationships by integrating disparate sources
• Transform these representations to conform to other frameworks of entities and relationships”
( Chrisman 1997:5)



A GIS as a Toolbox
"a powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes. This set of tools constitutes a GIS." (Burrough, 1986:6).
Or
“tools that allow for the processing of spatial data into information, generally information tied explicitly to, and used to make decisions about, some portion of the earth.” (DeMers 1999:7)

GIS Defined by Function
“… automated systems for the capture, storage, retrieval, analysis, and display of spatial data.”
(Clarke, 1995: 13).

GIS as an Information System
"An information system that is designed to work with data referenced by spatial or geographic coordinates … a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data" (Star and Estes, 1990, p. 2).

Duecker's (1979:20) definition has survived the test of time
"A geographic information system is a special case of information systems where the database consists of observations on spatially distributed features, activities or events, which are definable in space as points, lines, or areas.
A geographic information system manipulates data about these points, lines, and areas to retrieve data for ad hoc queries and analyses" (Duecker, 1979, p 106).

Geographical Information System (GIS) … defined
– A GIS is a computer based system for the management of geographic data.
– Geographic data is any data that is geographically referenced i.e. location known.
– Information implies that data are organized to yield useful knowledge
– System implies GIS is made up of several inter-related and linked components with different functions