A Geographic Information Systems (GIS) is a computer system for managing spatial data. The word geographic implies that location of the data items are known in terms of geographic coordinates (latitude, longitude). The word information implies that the data in a GIS are organized to yield useful knowledge, often as coloured maps and images, but also as statistical graphics, tables, and various on-screen responses to interactive queries. The word system implies that a GIS is made up from several interrelated and linked components with different functions. Thus, GIS have functional capabilities for data capture, input, manipulation, transformation, visualization, combination, query, analysis, modelling and output. A GIS consists of a package of computer programs with a user interface that provides access to particular functions.