Issues and Solutions to Displacement in Map Generalisation

Displacement is one of a number of methods used to improve the legibility of symbolised features in a map. In this paper a number of alternate paradigms for displacement are considered and compared. It is apparent that effective displacement can be achieved by sharing small movements among a group of objects in order to minimise loss of positional accuracy and maintain the gestalt and topology of the map objects. The proposed algorithm works by considering, for each object in turn, a number of alternate positions close to its current location and the location which minimises overlap among the neighbouring objects is chosen. In contrast to other approaches to the modeling of displacement, this idea is relatively simple but produces topologically consistent solutions to the displacement of large numbers of objects in very short order with very low processing overhead. This paper describes the algorithm and illustrates its application and evaluation. Suggestions for further work form part of the conclusion.