ABSTRACT
Spatial data exist mostly in map form. Maps are, in fact, well known and used tools for recording, storing and retrieving spatial data. Several characteristics of maps are of importance in any computerized application of mapped data. These are: (1) maps can contain very large volumes of data; (2) spatial relationships between entities are explicitly represented in the map structure; (3) attribute data, associated with the spatial entities, can be represented by a variety of techniques, e.g., shading, explicit feature codes, variable line widths, etc.; and (4) maps can be used manually, frequently without any special equipment. In short, the field of cartography has, over the years, moved toward the optimization of the recording, storage, and retrieval of spatial data in a graphic format. The design and implementation of computer techniques to replace maps must adequately consider the above items and include methods for accomplishing all the tasks implicit in the map characteristics as identified above.
