Figs. 7 and 8 show a comparison of DTM sections produced by the proposed algorithm ((a) and (c)) with those produced by the algorithm by Kraus and Pfeifer (1998) ((b) and (d)) using the same data. From Fig. 7, it can be seen that the algorithm proposed in this paper performed better both in terms of smoothness of the DTM and in reproducing the physical features of the terrain. The presence of humps in the DTM in (b), caused by the limited number of ground points in the data, should be noted.