The Application of Spatial Similarity in the Automatic Result Evaluation of Cartographic Generalization

Cartographic generalization is a cartography which selects, simplifies and generalizes objects in map according to the cartographic purpose, map scale and geographical features of the generalized area. This process creates a new map which should keep the basic geographical features of the generalized area. In map and GIS, the basic geographical features of an area are mainly reflected by spatial objects´ shape, spatial distribution density, their distance relations, direction relations and topology relations. Undoubtedly, whether the generalized objects are greatly similar to the original objects in shape, distance, orientation, topology and distribution density is one of important indexes in result evaluation of cartographic generalization. Usually these quality indexes are evaluated by cartographers with their oculars. Obviously this method is very inefficient and the obtained result is subjective and qualitative. Considering the special characteristics of cartographic generalization, this work divides spatial similarity into shape similarity, distance similarity, orientation similarity, topology similarity and distribution density similarity and presents the methods to measure these similarities. Then we use these methods to evaluate whether the result of cartographic generalization keeps the basic geographical features of the generalized area. Many experiments show that the application of spatial similarity measure in the result evaluation of cartographic generalization is reasonable. In addition, it can promote the result evaluation of cartographic generalization to become automatic and quantificational.