A spatial data model and a topological sweep algorithm for map overlay

Abstract

One of the most general query problems in spatial information processing is the map overlay operation that computes from one or more thematic map layers a new map by using an overlay function. Existing algorithms for vector-based map overlay operations suffer from one or more of the following disadvantages: lacking generality, inefficiency or poor adaptability to existing GIS-Systems. Furthermore only few proposals for parallel implementations of this operation have been made. In this paper we present a model for planar subdivisions similar to the well-known arc model. This model can be easily adapted to existing spatial access methods. Our overlay algorithm uses an overlay function and includes a fine-grain parallelism. The homogeneous structure of input and output maps allows pipelining of map overlay operations (coarse-grain parallelism).