Study On Improvement Of Filtering Of Lidar Point Clouds Based On Progressive TIN

Airborne LIDAR point cloud contains a lot of noise points,the non-topographic data is not conducive to the generation of high-precision DEM,therefore,point cloud filtering is an extremely important part in acquiring high-precision DEM.The foreign scholar(Sithole)has done some more convincing comparative experiments for the eight representative point cloud filtering algorithms,after analysis,the filtering algorithm based on the progressive cryptographic triangular network which is firstly proposed by Axelsson P.has better adaptability for the most of terrain,it can also obtain ideal filtering effects in complicated conditions.However,the point cloud filtering algorithm based on the progressive cryptographic triangular network needs to take much longer time and has a poor removal effect for low-rise buildings when dealing with point clouds.Aiming at the problems existing in the original algorithm,the algorithm in this paper first clusters the point cloud,extraits the feature point of each cluster and analyzes the topological character to determine the cluster is terrain data or not.The new algorithm emphasizes the overall determining whether a ground point,to abandon the original algorithm to judge point by point the way to enhance the filtering effect,reducing the amount of calculation and improve efficiency.On the basis of analyzing the domestic and foreign research status concerning the point cloud filtering,my thesis will study the following:?Improving the algorithm on the basis of the progressive cryptographic triangular network.Improving its efficiency,filtering effects of low buildings,etc.on the basis of the filtering algorithm of improved progressive cryptographic triangular network which is inherited the advantages of the progressive cryptographic triangular network,abandonning the conditions in the original algorithm where the angle is determined point by point and integrating the analyses of point cloud clustering and topological features,while enhancing the filtering effects,it has greatly reduced the amount of computation and improved operating efficiency.?Development of the LADIR-FILTER system.Combining the mixed programming technologies of ObjectARX and AutoCAD.NET to implement the secondary development of AutoCAD,programming the airborne 3D laser's point cloud filtering algorithm program LIDAR-FILTER.The program has completed the read of point cloud data,the construction of triangular network and several filtering algorithms,etc.and achieved the integration of complex point cloud data by using the AutoCAD which is easy to use.?Experimental Analysis.In order to demonstrate the effectiveness of the improved algorithms,the author selected the point cloud data of complex woodland and the point cloud data of residential areas with a wide variety of ground species to do experiment of point cloud filtering.Experimental results show that:The algorithm can achieve a better filtering for different types of terrain,it has been greatly improved compared with the original algorithms and only spend forty percent of the original use of time,it proves that the studied algorithms of this thesis are effective and efficient.