GEOGRAPHIC INFORMATION SYSTEM
The expansion of GIS is Geographic Information System which consists of three words, viz. Geographic, Information and System. Here the word 'Geographic' deals with spatial objects or features which can be referenced or related to a specific location on the earth surface. The object may be physical/natural or may be cultural/manmade. Like wise the word 'Information' deals with the large volume of data about a particular object on the earth surface. The data includes a
Set of qualitative and quantitative aspects which the real world objects acquire.
The term 'System' is used to represent systems approach where the complex environment (consist of a large number, of objects / features on the earth surface and their complex characteristics) is broken down in to their component parts for easy understanding and handling, but is considered to form an integrated whole form an aging and decision making. Now-a-days this is possible in a very short span of time with the development of sophisticated computer hardware and software. There fore, GIS is a computer based information system which attachesavariety of qualities and characteristics to geographical location (Fig.5)and helps in planning and decision making. A Geographic Information System(GIS) may bedefined in different manners. International Training Centre (ITC), Holland defined Geographic Information System (GIS) as a computerisedsystem that facilitatesthephases of dataentry, data analysis and data presentation especially incases when we are dealing with geo referenced data.
Indian Society of Geomatics (ISG) and Indian Space Application Centre (ISRO) defined GIS as a system which provides a computerized mechanism for integrating various geo information data sets and analysing them in order to generate information relevant to planning needs in a context. According to Centre for Spatial Database Management and Solutions (CSDMS), GIS is a computerbasedtoolformappingandanalysingthingsthatexistandeventsthathappenone earth.
Burrough (1986) defined GIS as a set of tools for collecting, storing, retrieving atwill, transfor mingand displaying spatial data from the real world for a particular set of purpose.
Arnoff (1989) defined GIS as ac omputer based system that provides four sets of capabilities to handlegeoreferenced data, viz. data input, data management (data storage and retrieval), manipulation analysis and data output.
From the above definitions, we can conclude that a GIS user expects support from the system to enter geo referenced data to analyse it in various ways and to produce output (maps and other) from the data. GIS draws on concepts andideasfrommany different disciplines, such as cartography, cognitive science, computer science, engineering, environmental sciences, geodesy, landscape architecture, law, photogrammetry, public policy, remote sensing, statistics and surveying. So, it involves not only the study of the fundamental issues arising from the creation, handling, storage and use of geographic information, but it also examines the impacts of GIS on individuals and society and the influences of society on GIS.
1 DEVELOPMENT OF GIS
Keeping long tradition of map making as background, G.I.S. has been developed during mid 20th century with the development of computer science. The data analysis of geographic locations was being done by computers in government organizations and universities in U.S.A. during 1950s and 1960s. The first true operational G.I.S. was developed by Dr. Roger Tomlinson, Department of Forestry and Rural Development , Canada. It was called as Canada Geographic Information System (CGIS) and was used to store analyse and manipulateland related data. Dr.Roger Tomlison was also known as the 'Father of G.I.S'. In1964, alaboratory
Of Computer Graphics and Spatial Analysis was established at the Harvard Graduate School of Design by Howard T. Fisher. This organization developed a number of important the oretical concepts of spatial data handling and in 1970 sit distributed seminal software code and system such as 'SYMAP', 'GRID' and 'ODYSSEY'. This inspired subsequent commercial development. By early 1980s, M&S Computing (later Intergraph) and Environmental Systems Research Institute (ESRI) emerged as commercial vendors of G.I.S. software. ESRI released ARC/Info and ARC View software in 1981 and 1992 respectively. By the end of 20th Century, the development of ARCView enabled viewing G.I.S. data through internet and eliminated many of the hardware and licensing expenses of software packages. Since then a number of organisations anduniversitieshavebeendoingresearchinthefieldofG.I.S.anddeveloping user friendly softwares . Now there is a growing number of free, open source G.I.S. packages which run in a wide range of operating systems and perform specific tasks.
2 REQUIREMENT OF GIS
Primarily deals with geographic data to be analysed, manipulated and managedinan organized manner through computers to solve real world problems. So, GIS operation requires two things - computer system and geographic data.
3 COMPUTER SYSTEM
Itincludes both hardware and software. GIS runs through computer system ranging from portable personal computers (PCs) to multi-user super computers which are programmed by wide variety of software languages. In all ranges, there area number things, that are essential for effective GIS operation. These include: 1) a processor with sufficient power to run the software, 2)sufficient memory for the storage of large volumeofdata,3)a good quality, high resolution
colour graphic screen and 4)data input and output devices (for example digitizers, scanners, keyboard, printers and plotters).
There are a wide range of software packages for GIS analysis, each with its own advantages and disadvantages. Eventhoselists are too long to be mentioned here, the important onesare different versions of ARC View, ARC Info, Map Info., ARC GIS, Auto Cad Map etc.