7Urban 3D Building Extraction from LiDAR and Orthoimages
7.1Introduction
During the past decade, digital photogrammetric methods for automatic digital surface model (DSM) or digital terrain model (DTM) generation have become widely used due to the efficiency and cost-effectiveness of the production process. The performance of these systems is very good for smooth terrain at small to medium scale when using small and medium resolution imagery. However, it decreases rapidly for complex scenes in dense urban areas using high-resolution imagery. The degradation in the performance of photogrammetric processes is mainly due to the failures of image matching, which are primarily caused by, for example, occlusions, depth discontinuities, shadows, ...
