A rubber sheeting algorithm for non-rectangular maps

Inherent errors in the conversion process (from maps to digital information) cause variations in the location of common boundary lines between adjacent maps. In order to eliminate these discrepancies and define a continuous database, the popular practice is to adjust the map's boundaries. Preventing relative distortions between the map boundaries (which get altered) and the content of the map necessitates correcting and geometrically improving the map's contents - a process known as "rubber sheeting". The paper presents a new method for rubber sheeting, which is not dependent on the shape of the closed polygon circumscribing the map (to be improved), or on the number of points defining its perimeter. The method also covers the various possible relations between maps, such as adjacent maps, a map included completely within another map, a group of maps, etc. The algorithm is based on a non-rectangular bilinear interpolation over the entire area of the map. It determines systematic and random corrections, and subdivides the maps into separate influencing zones as a function of the map perimeter's shape. The process ensures homogeneity in each map by itself, and, therefore, continuity over an entire database. (C) 2000 Elsevier Science Ltd. All rights reserved.