Research On The Methods Of Surface Reconstruction Of Urban Dense Point Cloud

With the development of flying platform and sensor technology, the ability to obtain spatial information is gradually improved. Especially the appearance of low-altitude oblique photography and its data processing methods, which make means more abundant to achieve true urban 3D information. In this dissertation, parts of the methods and algorithms for oblique photogrammetry’s data processing are studied with experiments. The main work in this dissertation is listed as follows:1. The key technology of data processing methods of oblique photogrammetry has been combed; the research status of the related technology has been introduced. The above have laid a foundation for the surface triangulation of urban point cloud, the texture mapping of mesh model, the simplification of mesh model and the multi-resolution model.2. The exiting point cloud region-growing triangulation algorithm has been analyzed, and its problems for handling dense urban point cloud have been summed up. On this basis, an improved strategy to traverse the PTE data structure has been proposed for the corner’s not fully growing of urban dense point cloud. Related experimental results have shown that:the improved algorithm is able to handle dense urban true 3D point cloud, and can solve the corner’s not fully growing problem which the exiting method cannot do.3. According to the technical characteristics of oblique aerial photogrammetry, the problems of the exiting multi-view texture mapping methods of urban 3D modeling have been further analyzed and the relevant texture mapping strategy has been changed, which have improved the visibility guidelines and adjacent consistency criteria of texture selection. And an optimization strategy for seam constrained has been put forward. Experiments have shown that the improved strategy is correct in multi-view texture mapping of urban modeling.4. The importance of using LOD (Level of Detail) technology has been established from 3D visualization. Base on the above, the strategy of meh model’s simplification has been introduced in detail. Experiments on texture mapping of urban multi-resolution models have been carried out, and archived good results. At the same time, the simplified mesh models have been reconstructed by triangulation algorithm aforementioned. And the adaption of the algorithm has been analyzed for dealing with different density urban point cloud through statistics of holes’ proportion. In the case of certain holes’ proportion threshold, the limiting value of urban point cloud’s density which is suitable for the triangulation algorithm has been given.