AUTOMATIC DERIVATION OF SKELETON LINES FROM DIGITIZED CONTOURS

Skeleton lines, i.e. ridge and drainage lines, are of essential importance for the description of terrain surfaces. Existing contour maps contain these lines implicitly. The paper presents two approaches for automatic derivation of skeleton lines from digitized contours. One is a vector-based approach, which uses aspect information from the given contour set as a clue for the derivation. Tracing the aspect vectors, slope lines are obtained and the one with minimum slope in the surroundings is chosen as the desired skeleton tine. The other approach is based on raster data processing techniques. Treating the given contour set as a graph, medial axes can be computed by means of suitable algorithms. Parts of medial axes, i.e. those between two parts of the same contour line, are picked out, connected and used as the approximate skeleton lines. In a further step heights can be assigned to the skeleton lines, e.g. by linear interpolation between two adjacent contours. Using both the given contours and the automatically derived skeleton lines, high-fidelity Digital Terrain Models can be generated. The paper is complemented by relevant practical examples.