ABSTRACT
Geographic Information Systems (GISs) serve the purpose of maintaining, analyzing and visualizing spatial data that represent geographic objects, such as mountains, lakes, houses, roads, tunnels. For spatial data, geometric (spatial) attributes play a key role, representing e.g. points, lines, and regions in the plane or volumes in 3-dimensional space. They model geographical features of the real world, such as geodesic measurement points, boundary lines between adjacent pieces of land (in a cadastral database), lakes or recreational park regions (in a tourist information system). In three dimensions, spatial data describe tunnels, underground pipe systems in cities, mountain ranges, or quarries. In addition, spatial data in a GIS possess non-geometric, so-called thematic attributes, such as the time when a geodesic measurement was taken, the name of the owner of a piece of land in a cadastral database, the usage history of a park.
