Research On Geometric Calibration Of Earth Observation Satellite Laser Altimeter

In recent years,Satellite mapping technology has changed rapidly,resolution satellite image has exceeded the sub-meter level,but for the products of resource investigation,environmental monitoring,polar mapping,disaster emergency and other industries in the field of surveying and mapping have been limited by elevation accuracy.In order to make up for the lack of domestic product stereo mapping elevation accuracy,some experts and scholars proposed to use stereo mapping camera and spaceborne grohe to composite mapping in one platform as a new way to improve the accuracy of satellite stereo mapping.However,the accuracy of the laser altimetry data is poor,and it is difficult to obtain the ground control data for on orbit geometric calibration.In order to solve this problem,this paper studies the geometric calibration method of spaceborne laser altimeter system and error compensation principle.Studied the principle of spaceborne laser altimetry and the whole system error propagation.With the measurement principle and system of spaceborne laser altimeter system structure as the starting point,to recognize the various parameters which effect the laser data processing precision of satellite in orbit,and the running state of the laser data processing precision,Based on the theoretical analysis and simulation modeling,the error propagation of laser measurement system is evaluated,and the error sources are divided into two categories:satellite measurement platform error and system external environment error.The main research contents and innovative achievements are as follows:(1)The geometric processing flow of spaceborne laser altimeter data is studied and the rigorous geometric model of spaceborne laser altimeter is proposed.According to the principle of spaceborne laser ranging,atmospheric propagation delay,global tide and the influence of surface features on laser echo signal,a rigorous geometric model of laser altimeter is established.Different from the traditional optical stereo mapping,as the active remote sensing method,the laser ranging is one of the error sources that must be considered,aiming at the difficulties of meteorological data acquisition,accuracy of the comparison,we analyze the existing high precision global atmospheric model,and apply to satellite laser ranging delay correction method,in order to meet the global high precision spaceborne laser mapping requirements,the global solid tide correction model and ocean tide correction model are applied to the laser altimeter data processing as well.(2)Based on terrain matching,the calibration method of spaceborne laser beam is put forward.Because of the error of satellite attitude,laser grohe installation error and the laser deviation,the laser pointing accuracy is not good enough,so it is not possible to directly use the laser detector arranged on the ground to make the geometric calibration.Aiming at the above problems,this paper puts forward a method of laser beam direction calibration based on terrain matching,based on the initial height data of laser,the laser beam is calibrated by combining the precision terrain data to the laser beam.Firstly,the feasibility of the geometric calibration method for laser exit direction is verified by the simulation data,and the SRTM-DEM data is used to determine the geometric calibration of Ziyuan 3(02)laser altimeter.It proved that the method proposed in this paper can effectively improve the precision of laser plane positioning and provide the key support for the field calibration of spaceborne laser altimeter system.(3)A new method for high precision calibration of spaceborne laser based on waveform matching and calibration field coordination is proposed.Large area terrain data can be used to accurately calibrate the direction of laser emission and improve the position accuracy of laser footprint,and the final result of the laser altimeter system is the compensation of the laser exit direction and the ranging value.In this paper,a method based on laser waveform matching and calibration field calibration is proposed,and the applicability of the two methods is discussed.Laser geometric calibration based on waveform matching is a kind of non real time data processing and calibration method which is not dependent on fixed site,the calibration site is suitable for dense urban areas and requires high precision DSM data support,however,the ground calibration method based on ground detector requires large area flat terrain,at the same time,this paper studies the layout scheme of laser detector in calibration field,in order to maximize the effectiveness of laser detectors.Finally,the feasibility and applicability of the laser calibration method based on waveform matching is verified by the simulation experiments,and the high precision geometric calibration method of spaceborne laser is verified by using ICESat/GLAS and ZY3-02 laser data.