Difinition of gis

INTRODUCTION:
        The discussion about GIS thus far has focused on data and software. Bu GIS are more than just these two entities. Taking a holistic systems view, GIS should also encompass: hardware, data collection/updating processes, dissemination of the products (maps, graphics, tables, reports), and the people who work with GIS along with their organizational structures. GIS can be viewed narrowly as just a tool, but should be viewed more broadly as an approach or way of working. We have now covered sufficient aspects of GIS to have an informed consideration of some definitions. The trouble is, there is no one single accepted definition. Maguire (1991) quotes no less than 11 definitions from the literature. Perhaps the most often quoted definition is that?of Burroughs (1986a, p. 6): “… a powerful set of tools for collecting, storing,retrieving at will, transforming, and displaying data from the real world for a particular set of purposes.” While this definition captures much of what GIS are about, it is a toolbox view rather than a systems view. The following definition from Dueker and Kjerne (1989, p. 7), therefore, is preferred with my modifications in brackets: … a system of hardware, software, data, people, organizations and institutional arrangements for collecting, storing, analyzing, [visualizing] and disseminating [spatial] information about areas of the Earth. Conventionally, and not so long ago, this chapter would have ended right here. But there has been some paradigm shifts of late and we must go stage farther and consider GIS within the context of geocomputation and geosimulation.

History of development: One of the first applications of spatial analysis in epidemiology is the 1832 "Rapport sur la marche et les effets du choléra dans Paris et le département de la Seine".[4] The French geographer Charles Picquet represented the 48 districts of the city of Paris by halftone color gradient according to the percentage of deaths by cholera per 1,000 inhabitants.
In 1854 John Snow depicted a cholera outbreak in London using points to represent the locations of some individual cases, possibly the earliest use of a geographic methodology in epidemiology.[5] His study of the distribution of cholera led to the source of the disease, a contaminated water pump (the Broad Street Pump, whose handle he had disconnected, thus terminating the outbreak) within the heart of the cholera outbreak.

E. W. Gilbert's version (1958) of John Snow's 1855 map of the Soho cholera outbreak showing the clusters of cholera cases in the London epidemic of 1854
While the basic elements of topography and theme existed previously in cartography, the John Snow map was unique, using cartographic methods not only to depict but also to analyze clusters of geographically dependent phenomena.
The early 20th century saw the development of photozincography, which allowed maps to be split into layers, for example one layer for vegetation and another for water. This was particularly used for printing contours – drawing these was a labour intensive task but having them on a separate layer meant they could be worked on without the other layers to confuse the draughtsman. This work was originally drawn on glass plates but later plastic film was introduced, with the advantages of being lighter, using less storage space and being less brittle, among others. When all the layers were finished, they were combined into one image using a large process camera. Once colour printing came in, the layers idea was also used for creating separate printing plates for each colour. While the use of layers much later became one of the main typical features of a contemporary GIS, the photographic process just described is not considered to be a GIS in itself – as the maps were just images with no database to link them to.
Computer hardware development spurred by nuclear weapon research led to general-purpose computer "mapping" applications by the early 1960s.
The year 1960 saw the development of the world's first true operational GIS in Ottawa, Ontario, Canada by the federal Department of Forestry and Rural Development. Developed by Dr. Roger Tomlinson, it was called the Canada Geographic Information System (CGIS) and was used to store, analyze, and manipulate data collected for the Canada Land Inventory – an effort to determine the land capability for rural Canada by mapping information about soils, agriculture, recreation, wildlife, waterfowl, forestry and land use at a scale of 1:50,000. A rating classification factor was also added to permit analysis.