Visualizing Terrain Models from Contours – Plausible Ridge, Valley and Slope Estimation

Applications such as modelling and animation of water runoff are becoming more and more important, and demand better surface orientation information than is available from traditional interpolation techniques and grids. Despite modern data acquisition techniques, contour maps 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 expressing the spatial relationships between sets of topographic contours. With these techniques the insertion of skeleton points into a TIN model guarantees the elimination of all "flat triangles" where all three vertices have the same elevation. Additional assumptions about the local uniformity of slopes give us enough information to assign elevation values to these skeleton points. In addition, various interpolation techniques were compared using the enriched contour data. Examination of the quality and consistency of the resulting maps indicates properties of the interpolation method that are required 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, and how it should behave under water runoff and erosion.