Structural analysis of DEM´s by intersection of surface normals in a three-dimensional accumulator space

This paper proposes a new methodology in DEM analysis in order to extract relevant information. The method proposed generates a set of 3D accumulators by using the DEM data. Each accumulator contains the number of intersections of the normals derived from the DEM surface. An alternative procedure has been developed in order to minimize the huge memory space required by a complete set of voxels. The principle consists of scanning the discrete space by a vertical plane. This plane, called a Voxel Wall, is composed of all the local accumulators. Two matrices are generated. In the first, named Values of the Accumulator Matrix (VAM), the positions x,y and the corresponding maximum value μ of intersections encountered in each column of the Voxel Wall are registered. The depth ζ of each μ is coded on the second matrix, called Depth of the Accumulator Maxima (DAM). The results provided by regular shapes such as hemispheres, cones, and pyramids, as well as those produced by deformations and/or linear translations, are analyzed. An exhaustive interpretation of these results requires the creation of a catalogue of all the criteria for describing a given shape, whether it be isolated or not. The procedure has been applied to some “real” DEM containing volcanic edifices, crest lines, and bulging shapes