chapter  11
18 Pages

Spatial data access methods for points, lines and polygons

Fundamental to all information systems, whether geographical or otherwise, is the need to search through a quantity of data that is often very large, in order to find a subset which satisfies the user's query. The distinguishing characteristic of the typical geographical data retrieval is that it is expressed in terms of spatial locations and spatial relationships. In generaL spatial queries may be either location-based or phenomenon-based, or a combination of the two. A location-based query specifies a location and asks what phenomena are to be found there. A phenomenon-based query specifies particular phenomena and asks where they are to be found.