Simplification of contour lines, based on axial splines, with high-quality results

Abstract

This paper introduces a new simplification method providing high-quality contour lines derived from the 3D point cloud, minimizing their energy. It combines the simplification potential and the splines with the generalized axial symmetry. Generating results similar to the topological skeleton, it applies to large-scale maps (1:5000–1:25,000). It significantly improves all geometric and shape parameters of contour lines, namely in flatter areas. Extensive cartographic testing on high spatial density point clouds using 17 invariants is performed. The outcomes indicate the significant potential of the proposed method. The simplified contour lines preserve the given vertical error, lie within the vertical buffer, are parallel, aesthetically pleasing, and have similar spacing; their artificial oscillations are significantly reduced. Unlike complex generalization methods, the proposed solution does not interfere with the DTM but performs only a correction of the cartographic representation of contour lines.