Vector to raster and raster to vector conversions
Map generalisation is a fundamental process in graphic communication of spatial information, and it has so far defied successful automation. It is concerned with information abstraction and may be considered in terms of semantic generalisation, which focuses on the meanings to be communicated, and in terms of geometric generalisation, which addresses the graphic and symbolic representation of the spatial data. Semantic generalisation employs processes of aggregation and classification to structure the meaning of information in an hierarchical manner, often involving overlapping hierarchies. Geometric generalisation and the associated issue of symbolisation can be viewed in terms of several main types of operation including the elimination of objects. Rather than removing spatial objects, as in elimination, the process of reduction is concerned with decreasing the constituent detail of lines, polygons and surface representations. This chapter also provides an overview of the stages involved in process control in automated generalisation.