Saturday, 2 July 2011
GIS provide powerful tools for integrating geographical information with Agriculture, forestry, Geology, Infrastructure, Fishery, National security, Disaster, Water quality, Air quality, Environmental issues, Economic, Marketing, Transportation, etc . Imagine that the GIS allows us to arrange information about a given region or city as a set of maps with each map displaying information about one characteristic of the region. For example, a set of maps that will be helpful for urban transportation planning have been gathered. Each of these separate thematic maps is referred to as a layer, coverage, or level. And each layer has been carefully overlaid on the others so that every location is precisely matched to its corresponding locations on all the other maps. The bottom layer of this diagram is the most important, for it represents the grid of a locational reference system (such as latitude and longitude) to which all the maps have been precisely registered.