OPENGIS PROJECT DOCUMENT 99 - 078 TITLE : Topological Operators for the Grid Coverage

Egenhofer's nine-intersection, well-known for vector representations, is de ned here on a raster, using a hybrid raster model, and then systematically transformed to yield functions which can be used in a convolution operation applied to a regular raster representation. Applying functions, the hybrid raster elements need not be stored. It becomes thus possible to determine the topological relation of two regions, given in raster representation, with the same reasoning as in vector representations. This contributes to the merging of raster and vector operations. It demonstrates how the same conceptual operations can be used for both representations, thus hiding in one more instance the di erence between them.