‘GIS’ comprising the three words ‘Geographic’ or ‘Geographical” Information’ and ‘System’ simply means that it is the system of analysing the information (data) collected from various fields about the earth (geo). When we use the word ‘geographical’ the concepts of ‘space’ and ‘time’ immediately comes to our mind. Thus the limits of the ‘GIS’ cannot be defined since the boundaries of information or data collected over time and space cannot be fixed. There has been some debate about the origin of the term ‘GIS’ and the date of initiation of working in this field, but it is clear that it is a relatively recent phenomena. The field of GIS is characterised by a great diversity of applications. GIS is actually an integrating system which combines the ideas of many areas like agriculture, botany, zoology, mathematics, philosophy, economics, surveying, photogrammetry, cartography, geography and so on.
It is very difficult to define GIS since there are many different ways of defining and classifying objects and subjects from which information or data are collected.
A Geographic Information System (GIS) is a system designed to capture, store, manipulate, analyse, manage and present spatial or geographic data. GIS applications are tools that allow users to create interactive queries (user-created searches), analyse spatial information, edit data in maps and all these operations. GIS sometimes refers to Geographic Information Science (Gl Science) which is the science underlying geographic concepts, applications and systems.
The first known use of the term ‘Geographic Information System’ was by Roger Tomlinson in the year 1968, in his paper ‘A Geographic Information System for Regional Planning”. Tomlinson is also known as the ‘Father of GIS”.
Every decision that we take today is largely driven by location and has spatial connotation directly or indirectly. In this unit we will learn about Geographic Information System (GIS) –a modern day spatial decision making system. GIS has come a long way from digital mapping to decision making, invoking simulations, creating networks, evolving models based on big geo-data analytics and all gearing for real-time decision making with prediction capability. That is where lies the power of geospatial domain and of which Geographic Information System is an important part. The users of this technology have multiplied manifold from few specialists in Universities, space research centres , government departments, and industry to a lay man. The usefulness of GIS is driven today by many pull and push factors and the rapid changes taking place around natural ecosystem.
Overview of GIS
A Geographical Information System (GIS) is a system for capturing, storing, analyzing and managing data and associated attributes, which are spatially referenced to the Earth. The geographical information system is also called as a geographic information system or geospatial information system. It is an information system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically referenced information. In a more generic sense, GIS is a software tool that allows users to create interactive queries, analyze the spatial information, edit data, maps, and
present the results of all these operations. GIS technology is becoming essential tool to combine various maps and remote sensing information to generate various models, which are used in real time environment. Geographical information system is the science utilizing the geographic concepts, applications and systems.
Geographical Information System can be used for scientific investigations, resource management, asset management, environmental impact assessment, urban planning, cartography, criminology, history, sales, marketing, and logistics. For example, agricultural planners might use geographical data to decide on the best locations for a location specific crop planning, by combining data on soils, topography, and rainfall to determine the size and location of biologically suitable areas. The final output could include overlays with land ownership, transport, infrastructure, labour availability, and distance to market centers.
Definition of GIS
The term GIS is most likely to change with changing technology and development of applications. Therefore, it is difficult to give a precise definition because of its dynamic character. However, a number of scholars have attempted to explain and define the term. Besides defining the term, these also show the trends of development in the field of GIS. Some of the definitions follow-
A Geographic Information System (GIS) is a system designed to capture, store, manipulate, analyse, manage and present spatial or geographic data.
GIS is a computer based system which collect, manipulate, analysis geospatial data and make easier decision making.
A special case of information system where the database consists of observation on spatially distributed features, activities, or events which are definable in space as points, lines or areas. A GIS manipulates data about these points, lines and areas to retrieve data for ad hoc queries and analysis.
Burrough – 1986
“A powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world.”
Department of Environment, London (DoE) – 1987
“A system for capturing, storing, checking, manipulating, analysing and displaying data which are spatially referenced to the Earth.”
Parker – 1988
“An information technology which stores, analyses, and displays both spatial and non-spatial data.”
Tomlin – 1990
” A Geographic Information System is a facility for preparing and interpreting facts that pertain to the surface of the earth.”
A GIS is an organized collection of hardware, software, geographic data and personal and designed to effectively capture, store, update, manipulate, analyze and display all forms of geographically referenced data.”
“as automated system for capture, storage, retrieval, analysis and display of spatial data.”
United States Geological Survey (USGS) – 1997
“A computer system capable of assembling, storing, manipulating and displaying geographically referenced information.”
Of all the definitions, it is clear that the most comprehensive definition has been given by Ducker. During 1980s many attempts were made to define GIS. Many of these seem to focus on parallel and duplicate views. Therefore, a committee headed by Lord Chorley was set up to find the best explanation for GIS. The committee suggested the following definition of
GIS “a system for capturing, storing, checking, integrating. manipulating, analysing and displaying data which are spatially referenced to the earth.” ( Lord Chorley )
Relation of GIS with other Information Systems
For establishing a definition of GIS, the understanding of its relationship with Computer Aided Design (CAD), Computer Cartography, Database Management System (DBMS), and Remote Sensing Information System is very important. There have been conflicting views regarding its relationship with above-mentioned sciences and systems. Sometimes it is argued that GIS is a part of these systems.
Concepts of Cartography, Remote Sensing and GIS Now let us understand in brief the various systems to have a true understanding of their relation with GIS. Computer Aided Design (CAD) systems have been developed mainly for designing and drafting new objects. These are graphic based and features are represented by symbols known as primitives. The CAD systems have only elementary links to data bases. Automated assignment of symbols cannot be done in CAD systems which have limited analytical capabilities.
Computer Cartographic Systems focus mainly on data retrieval, classification and automatic symbolisation. However the main emphasis is on display rather than analysis, of the data. Only simple data structures are used in the systems of computer cartography. These data structures do not have any information regarding topology. The database management system (DBMS) can be linked in the systems of computer cartography for simple retrieval processes which are usually undertaken. It is notable that computer cartography systems have many facilities for designing and producing
High quality maps in vector format. Database management system (DBMS) are the software systems which have been developed and optimised for storing and retrieving non-graphic attribute data. It is notable that these systems have limited graphical retrieval and display capability. Only a short term retrieval and update of relatively small quantities of data can be done by DBMS. These systems are designed for only simple analytical functions and have very limited capabilities for spatial analytical operations.
Remote sensing systems perform the task to collect, store, manipulate and display raster data which are derived from scanners mounted on aircrafts and satellite platforms. These systems are capable of handling any data in raster format and they have limited capabilities for handling vector data. As such these are unsuitable for operations which are carried out for network analysis. These systems also have very limited capabilities for handling attribute data and have poor links to DBMS. Apart from these limited capabilities, Remote sensing systems have very sophisticated facilities for enhancing and classifying data. However, most of these systems have limited capabilities for spatial analysis.
- Concept of cartography Remote sensing and GIS by K.K.Maltiar and (Mrs) S.R.Maltiar