Research On Lidar Data Producing DLG And Quality Control

The construction of digital city geospatial framework put forward higher requirements for fundamental geographic information resources. As an important part of the spatial data, the DLG data is the basic data necessary for the state’s construction and urban planning. The DLG data, as a kind of intelligent data set, its producing, updating and quality control has been a hot topic in the field of surveying and mapping.The traditional producing mode of DLG is time-consuming and low efficiency, it requires a lot of field work, what’s more, it is difficult to update the DLG when necessary, as a result, it doesn’t meet the requirement of the construction of digital cities for the latest and highly efficient fundamental geographic information resources. In recent years, airborne LIDAR technology has gradually developed into an efficient and accurate means of getting three-dimensional spatial data, and is widely used in areas such as mapping, military and environmental monitoring. The most direct use of LIDAR data is to quickly generate accurate Digital Elevation Model(DEM), as most of the existing LIDAR systems can also provide high-resolution image data, Digital Orthophoto Map (DOM) can be obtained through joint processing on the image and point cloud data. Based on high-precision DEM and DOM, the DLG can be produced with proper editing. Compared with the traditional DLG producing method, by processing LIDAR data to produce DLG has a shorter mapping cycle and a higher degree of automation. So as to ensure the accuracy of digital products, and make sure the produced products meet users’requirements and quality standards, it is necessary to implement quality control in all aspects of the producing process. The research of this thesis is just based on this background, and the main contents of this thesis are as follows:1. The survey principle and technical characteristics of the airborne LIDAR system are introduced. At the same time, the airborne LIDAR data structure and the characteristics of the point cloud data are discussed.2. The principle of LIDAR data filtering is analyzed, some typical data filtering algorithms are studied, and filtering difficult areas are summarized.3. Outlier elimination methods of airborne LIDAR data before data filtering are discussed in detail, including the histogram, the shaded relief map, the three-dimensional circle excluding the outlier, gross error detection algorithm based on voxel division. It can play a quality control role for data preparation before data filtering.4. The quality control problem of DEM which deprived from airborne LIDAR filtering data is studied. Since no filtering algorithm can completely separate the ground points from the feature points, in order to improve the quality of the DEM deprived from LIDAR data, further probe on the ground points after the filtering is done to remove the residual non-ground points in the ground points.5. The method of producing DLG based on airborne LIDAR data is expatiated, and the key issues during the producing process are analyzed. Finally,1:2000DLG by processing airborne LIDAR data is produced. Through the plains and the mountains experimental data verify the quality control techniques.The feasibility of using airborne LIDAR data to produce DLG is proved by thesis research and experiment results. Outlier elimination of airborne LIDAR point cloud data before data filtering can improve the validity of the filtering result. Gross error detection on the ground points after data filtering can improve the accuracy of the DEM, play a certain role on the control of the final product’s quality.