Parallel processing for geographical applications: A layered approach

. Significant trends in the processing of geographical data require increasingly powerful software and hardware, consistent with the exploitation of parallel computing. Despite recent progress in technology, exploiting parallel processing is still difficult so that few applications have been developed in the environmental and geographical domains. Key issues which must be addressed in the design of parallel geographical software are described with reference to designs for three examples which use grid and raster data. The implications for parallel processing with vector-topological data are then explored. The emphasis is upon MIMD architectures using strategies of decomposition into subareas, and upon the need to facilitate development of parallel geographical applications by encapsulating the parallelism in a low-level layer of software, forming a skeletal framework upon which application algorithms can be built. The parallel layer will support distribution of datasets across the multiple processors, and the creation and collation of datasets from those processors.