| With the rapid development of earth observation technology,satellite laser altimetry has attracted more attention.The GF-7 and terrestrial ecosystem carbon monitoring satellite will be launched during the next three years,and both of them will be equipped with laser altimeter.What's more,the ZY3-02 satellite has succefullly been launched on May 30th,2016,on which the first earth observation laser altimeter of China was loaded,mainly for the function and performance test of laser,to explore the feasibility of elevation control points data acquisition,and use the data to improve the accuracy of optical satellite stereo images without ground control points.In order to fill up this blank of China,and boost the improvement of cooresponding technology,the research for civilian earth observation satellite laser altimetry data processing and application is urgent and required.This dissertation mainly fouces on the research of some key technologies of satellite laser altimetry data processing and application,in order to demand the requirements of the ZY3-02 satellite laser altimetry data.The satellite laser altimetry rigorous geometric mode is constructed,and the method for on-orbit geometric calibration of laser altimeter is proposed,then the automatic extraction and application of elevation control points for space-borne optical stereo images are implemented and validated using ZY3-02 satellite laser and image data.This paper summarizes the development status at home and abroad about the satellite laser altimeter system,and compares the three different techniques:satellite radar altimetry,satellite laser altimetry and satellite laser ranging,which highlights the characteristics and value of satellite laser altimetry in the first chapter.In the second chapter,the basic principle of satellite laser altimeter is summarized and defined,and the key hardware composition of ICESat/GLAS laser altimeter system,the method of data processing and product classification standards of GLAS data are introduced,which can provide reference for ZY3-02 satellite laser altimeter.In the third chapter,the construction of the rigorous geometric model is discussed,and the error sources which contain the ranging error,topography and atmospheric refraction and so on are analyzed.Moreover,the mistake of GLAS ATBD on plane position error caused by the atmospheric refraction is compared and analyzed.At last,the experiment of the actual GLAS and ZY3-02 satellite laser altimetry data is implemented.In the forth chapter,the on-orbit geometric calibration method of satellite laser is proposed,which contains the coarse calibration of laser pointing angle using terrain matching based on the referenced and existed terrain dataset,and the refined calibration based on ground detectors in the field.The simulated experiment of the laser pointing angle estimation based on the terrain matching method is demonstrated through the GLAS data.Also,the ZY3-02 satellite laser altimeter calibration is implemented according to the actual requirement,and after the calibration,the plane precision of laser footprint points can improve from 8km up to 15.0m,the elevation on the flat terrain can be improved from 90m to better than 1.0m even 0.5m near the calibration field.This conclusion for ZY3-02 is very inspiring.In the fifth chapter,the automatic extraction of laser generalized elevation control points is presented,and the method of multi-parameters and multi-criterion constraints for extraction is proposed,which combined the existing public DSM such as the SRTM and AW3D30 or other global terrain data,the ranging parameters such as the cloud,saturation,reflectivity and SNR and echo waveform parameters.The threshold of these parameters are discussed in order to ensure the accuracy and robust of laser elevation control points after selection.Then,the experiments of Tianjin and Taiyuan regions are implemented to validate that after selection the absolute elevation accuracy of GLAS footprint points is better than 1.0m,and nearly half of them is better than 0.5m.Although there is no waveform data,preliminary analysis of ZY3-02 satellite laser elevation control points selected by using the AW3D30 is demonstrated and the error is greater than 5.0m will be deleted.In flat area the result can reach to 1.0m compared with 1:2000 high accuracy DEM data in the North China experimental region.In the sixth chapter,the combined adjustment processing of satellite laser altimetry data and optical stereo images is discussed,and two adjustment methods based on the rigorous imaging model and rational function model are refined,which are aimed to resolve the same platform and different platforms or different time of satellite laser and image data.Then,the experiment using GLAS data,ZY3-02 satellite laser data and stereo images is presented,and the results indicate that the elevation accuracy of the stereo images can be effectively enhanced using laser altimetry data from GLAS or ZY3-02,both of them can reach to the level of 3.0m and ZY3-02 images in some test area even can reach to 2.0m.Consequently,classification system of laser altimetry data and product is discussed preliminarily,considering on the actual application requirements for earth observation satellite.The satellite laser altimetry data processing and application software based on the key techniques of this dissertation is introduced.The laser altimeter loaded on the ZY3-02 satellite is just used for hardware experimental test,and the basic parameter setting is not ideal,especially in the waveform sampling and recording function,which constraint the research depth of this thesis.But the result of satellite laser altimetry data processing,on-orbit geometric calibration and the combined adjustment between the image and laser altimetry data is valuable for ZY3-02 and the subsequent satellites of China,such as GF-7 the future high resolution stereo mapping satellite,terrestrial ecosystem carbon monitoring satellite and so on,all of them will be equipped with laser altimeter. |
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