Terrain Modelling Based on Contours and Slopes

Abstract

Good quality terrain models are becoming more and more important, as applications such as runoff modelling are being developed that demand better surface orientation information than is available from traditional interpolation techniques. A consequence is that poor-quality elevation grids must be massaged before they provide useable runoff models. This paper describes improved methods for extracting good quality terrain models from topographic contour maps, which despite modern techniques are still the most available form of elevation information. Recent work on the automatic reconstruction of curves from point samples, and the generation of medial axis transforms (skeletons) has greatly helped in the visualisation of the relationships between sets of boundaries, and families of curves. The insertion of skeleton points guarantees the elimination of all flat triangles. Additional assumptions about the local uniformity of slopes give us enough information to assign elevation values to these skeleton points. Various interpolation techniques were compared using visualisation of the enriched contour data. Examination of the quality and consistency of the resulting maps indicates the required properties of the interpolation method in order to produce terrain models with valid slopes. The result provides us with a surprisingly realistic model of the surface — that is, one that conforms well to our subjective interpretation of what a real landscape should look like.