A semiautomatic method for assigning elevation in contour maps

Assigning contour elevations during digitalization process of topographic charts can be a very time-consuming task and liable to human errors. The method here presented for this purpose is based upon the integration of three elements: the definition of nesting tree, a formal set of rules linking neighboring contour elevations and the concept of ambiguity interval. The information provided by the chart control points and its propagation on the nesting tree for ambiguity interval update allows to automatically evaluate a considerable number of elevations, typically 60%. The remaining curves are assessed with the help of an operator where an strategy is employed to minimize human interaction. At the end of the process, the typical figure describing the number of elevations requested by the system is around 20%