A GIS (Geographic Information System) is a computer application designed to capture, store, manipulate, analyze, manage, and present all types of geographical data, in addition to composing and printing maps. It combines a traditional database with a visual display of map features, such as points (e.g. houses), lines (e.g. streams and rivers), and polygons (enclosed areas such as lakes, habitat types, and town boundaries). A GIS can also incorporate image data, such as remote sensing imagery of the earth taken from satellites or aircraft, scanned paper maps, georeferenced drawings, etc. External data residing in spreadsheet, database, or plain-text files can also be mapped in a GIS as long as the data include geographic coordinates or can be joined with data that do. In addition, GIS software can access map layers from server-based databases and Internet Web Map Services (WMS).
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