Morphological transformation for the elimination of area features in digital map generalization

For the graphic representation of spatial data (e.g. a map), if the scale of the representation is reduced, then some area features will become too small to be represented, i.e. they need to be eliminated. This elimination procedure is part of the so-called generalization process. This paper describes some techniques in digital map generalization for this procedure, which employ several operators developed in mathematical morphology, a science of shape, form and structure. The techniques include three steps. These involve a process to reduce the size of every area feature using an erosion operator (leading to the disappearance of those small area features which need to be eliminated), a process to recover the size and shape of every area feature that has just been eroded, and a process to simplify the boundaries of recovered area features so as to suit the representation at a smaller scale. The models used in these techniques provide a mathematical basis for area elimination in digital generalization of map and other spatial data. The techniques described in the paper have been tested using examples, which demonstrate the potential for successful application.