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GENERATION OF ROOF TOPOLOGIES USING PLANE FITTING WITH RANSAC

For the acquisition of Digital Surface Models (DSM), LIDAR has proven a reliable and accurate observation technique. In contrast to the generation of a Digital Terrain Model, which can be derived from the corresponding DSM by morphological filtering, the extraction of building models from the DSM requires more sophisticated modelling techniques. Here we follow a data-driven approach. The high density of recorded airborne LIDAR data inspires to develop concepts which are relying on the bulk of data. Accordingly, we have decided to reconstruct building models from LIDAR data by fitting surface planes with the well-known RANSAC technique. After the mere plane fitting, plane regions have to be formed and adjacent plane regions are intersected. A possible separation of roof faces by vertical walls is taken into account. By exploiting the established neighbourhood relations of all plane regions and the computed intersection lines the 3D coordinates of corner points of the building can be estimated. A global adjustment is performed in which corrections to the plane parameters are provided in order to conserve the planarity of the polyhedral surfaces. Our main focus in this paper, however, is the creation and reorganization of the roof topology. Insignificant structures in the building model have to be eliminated; this corresponds to unifications or splitting of corner points. It is crucial to preserve consistency within the reorganization process. In particular, in the horizontal projection of the roof, the edges are allowed to intersect only in the corner points. The polygons confining the planar roof surfaces have to be closed and consistently oriented. The paper proposes rules for the reorganization of the topology and illustrates our overall approach for building reconstruction with an example.