Detection And Repair For Missing Area Of Airborne LiDAR Point Cloud Data

As a new type of technology,airborne LiDAR(Light Detection and Ranging),which integrates a variety of technologies,has become one of the most important technical means for obtaining geo-spatial data.It is mainly used for quickly obtaining 3D space information of surface objects,and generating digital products such as DSM(Digital Surface Model),DEM(Digital Elevation Model)and so on.As a technological innovation in the field of surveying and mapping,this technology is becoming a research hotspot in many fields for its unique advantages.Due to the fact of the building blockage and/or water absorption during the scanning process of the airborne LiDAR measurement system,the airborne LiDAR data inevitably produce missing areas,which have significantly impacted the subsequent application of the point cloud data.Based on the summarization and analysis of the existing research results,this essay focuses on the detection and repair of the missing regions through the programming implementation and experimental verification,the improvement of the related algorithms are completed.The major contributions and achievements of this paper are as follows:(1)The hardware composition and measuring principle of airborne LiDAR measurement system are introduced in detail,and the characteristics of the acquired data are analyzed.Based on the analysis of the common methods of outlier elimination and filtering methods,adopted a outliner eliminating method based on the statistics of elevation distribution and a morphological filtering method are used for the subsequent data processing.Experiments show the effectiveness of these methods.(2)In order to obtain the boundary information of the missing areas in the airborne LiDAR data,a boundary extraction algorithm based on pre-positioning is proposed.By meshing the data and using the seed algorithm to searching continuous holes in the mesh which is greater than a given threshold,the boundary meshes are obtained by expanding out of continuous holes and the boundary feature points in the boundary meshes are determined by the maximum angle difference method.Experimental results show that the proposed algorithm can quickly and accurately detect the boundary feature points of the missing areas.(3)In order to repair the missing areas in the airborne LiDAR data,an improved algorithm based on ground point surface fitting is proposed to repair the missing areas.By filtering the data to obtain the ground points and fitting the surface by moving least square method,the points with higher height values in the neighborhood points are identified by statistics and projected to the surface.Finally,the coordinates of the point to be repaired are determined by the intersection point of the straight line and the nearest neighbor interpolation method is used to determine the height value of the point to be repaired,so that the missing area can be repaired.Experimental results show that the repair effect is closer to the real situation.(4)Through applying this algorithm to airborne LiDAR data provided by the Third National Lidar Conference,repairing the missing areas of data to verify this algorithm has certain practicality.