Geometric Calibration And Validation Of Domestic Space-borne Laser Altimeter

Spaceborne lidar is also known as space-borne laser altimeter,because it uses satellite platform,its orbit is higher and its observation range is wider than airborne radar.Space-borne laser altimeter has advantages of large coverage,high ranging precision,it is widely used in forestry and other fields.Satellite laser altimeter will become a new means of acquiring elevation control points,it can solve the problem that control points of inaccessible and foreign areas are difficultly acquired.Utilizing high precision elevation control points and optical images to improve the stereo mapping accuracy with block adjustment,it will provide the foundation and assurance for the subsequent global observation.A number of system errors come into being in the process of launching of satellite.Using on-orbit geometric calibration to eliminate system errors is necessary.In this paper,the first domestic earth observation laser experimental load(ZY-3 02)is as the study object.Firstly,studying on-orbit geometric calibration method of domestic and foreign laser altimeter,summarizing the principle and process of each method,analyzing the advantages and disadvantages of each method.Building the space-borne laser strict geometric model,analyzing the main error sources using the model.Verifing the elevation accuracy after on-orbit geometric calibration through the relative and absolute validation way.Taking tianjin area as an example,the laser altimeter data aids RFM model to study the block adjustment,it proves feasibility of using the laser altimeter datas along with optical images to take block adjustment.The method can improve the three-dimensional positioning accuracy.In this paper,the main research contents and the specific work is as follows:(1)Summarizing the main existing space-borne laser altimeter system of domestic and foreign,explaining their work principle,and building the strict geometric model with the relation between orbit and attitude parameters acquired and installing relationship in the body coordinate system,analyzing the main error sources.Establishing sloping topography ranging error model,analyzing the influence of orbit altitude,laser pointing angle,the influence of the surface slope on the ranging accuracy.Studying on-orbit geometric calibration methods of satellite laser altimeter,analyzing advantages and disadvantages of each method,this is very meaningful for selecting the on-orbit calibration method of domestic laser altimeter.(2)According to the characteristics of ZY-3 02 laser altimeter,on-orbit calibration method using ground detector method is suitable.Inferring calculative process of ground detector method.Acquiring orbit,attitude angle,laser range value through unpacking the original laser data which return from the satellite,using strict geometric model to calculate the laser altimeter data,and then analyzing the quality of the laser altimeter data.Verifing the elevation accuracy of on-orbit geometric calibration with the relative and absolute way.(3)Taking tianjin area as an example,studying the feasibility which the laser altimeter data assists RFM model to take block adjustment.Using stereoblock adjustment model and RFM system error compensation model to verify the model that the planar and elevation control datas are split and calculated independently.The experimental results show that the model established can improve the direct stereo positioning accuracy,and the accuracy is almost the same to the traditional stereoblock adjustment model,which can prove the feasibility of the model.The conclusion can provide theoretical support for the laser altimeter data assistting RFM model to take block adjustment.