| As a new means of data acquisition, accuracy of airborne LiDAR(Light Detection And Ranging) system has been the focus of attention. Whether the results can be applied directly to basic surveying and mapping products is a question we must answer when carrying out large-scale airborne LiDAR engineering application. While systematic errors are the main factors of affecting the accuracy of airborne LiDAR system, elimination of systematic error has been a key issue affecting and constraining the development and application of airborne LiDAR. Therefore, to attain high-accuracy airborne LiDAR data, it is of great theoretic and practical value to research the key techniques and methods of the elimination of systematic errors.This paper takes the strip adjustment as the key technique and main research content. The related theory, techniques and methods of airborne LiDAR data's systematic error processing are studied to an extent. Facing to the advanced theories of airborne LiDAR strip adjustment, grasping the status and trends of technological development, according to characteristics of LiDAR data, combining of theoretical analysis, the method design, algorithm implementation, new strip adjustment methods are proposed and fulfilled. The main content and research issues of this thesis are listed as following.①Analyze the error sources and their influences on the airborne LiDAR data qualitively and quantitively. Airborne LiDAR system integrates multiple subsystems, its positioning accuracy will be influenced by INS, ranging, GPS positioning, system integration and other errors. Impact of these subsystems on the results of laser footprint positioning will usually render a systemic, distorted position results in varying degrees. In order to achieve three dimensional surface information of high precision, we have to study size and influence of those errors', and to take certain measures to reduce the effect of these errors. From the position equation of airborne LiDAR system, this paper analyses the error propagation of LiDAR system. The errors such as the INS, GPS positioning, ranging, laser scan angle are discussed detailedly, the influenced rule of those errors are deeply studied. The academic positon precision are discuss and the stimulant numerical value of LiDAR system are deduced by the precision of its composite.②Study the LiDAR strip adjustment theory. LiDAR strip adjustment's performance potential as well as limitations several aspects should be considered, including surface representation, error characteristics of LiDAR, surface comparisons, modeling, and adjustment techniques. So our paper reviews these fundamentals of the underlying theory, and then the most important techniques of LiDAR strip adjustment are discussed. on this basis makes a complete strip adjustment process; the key issues involved in the study are given solution.③Propose Least Z-Difference(LZD) and Least Normal Distance(LND) two matching algorithms based on 3D surface matching without control points. Effectively eliminate airborne LiDAR point cloud data systematic errors between strips. Experimental results show that: the accuracy of airborne LiDAR strip adjustment based on LND and LZD can both meet the project accuracy requirements; compared to commercial software TerraMatch, LZD and TerraMatch accuracy are at the same level, and the proposed algorithm can successfully complete the task of strip adjustment when TerraMatch software failure.④Introduce the Gauss-Markoff model to the three-dimensional surface matching based on uncontrolled airborne LiDAR strip adjustment method for the first time.Experimental results show that after reasonable parameters configuration of the Gauss-Markoff model, improved strip adjustment method can significantly improve the adjustment accuracy.⑤extend traditional photogrammetric strip block adjustment principle to airborne LiDAR point cloud data processing, propose a airborne LiDAR strips block adjustment method which can effectively reduce the strip adjustment caused by error accumulation .
|
PDF Full Text Request