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URBAN 3 D GIS FROM LIDAR AND DIGITAL ORTHOIMAGES

This paper presents a method, which integrates image knowledge and LiDAR point cloud data for urban DEM and DBM (digital building model) generation. The DBM is an Object-Oriented data structure, in which the building is considered as an building class, i.e. an entity of the class, in which the attributes of each building include roof types, coordinates of polygon of the roof, height, surfaces, parameters describing surface, and the LiDAR point array. Each polygon represents a roof of building. This data structure is flexible for adding other building attributes in future, such as texture information. Using image knowledge, we developed a new method of interpolating LiDAR raw data into grid DSM with considering the steep discontinuities of buildings. In this interpolation method, the LiDAR data points, which are located in polygon, first have to be determined, and then interpolation via planar equation is employed for grid DSM generation. The basic steps of our research are (1) Edge detection by digital image processing algorithms; (2) Completely extraction of the building roof edges by digital image processing and computer-human interactive operation; (3) Establishment of DBM; (4) generation of DEM by removing surface objects. Finally, we implement the above functions by MS VC++ programming. The outcome of urban 3D DSM, DEM and DBM is exported into urban database for future urban 3D GIS.