The presentation reviews the development and application of geographic information systems (GIS) in terms of its capacity to store information about the world as a collection of thematic layers that can be linked together by geography. The real world consists of many geographies which in GIS can be represented with a number of related data layers such as: hydrology, topography, land use, soil, streets, utilities, districts etc. GIS analytical capabilities provide access to raw data, which can then be aggregated or reclassified