Research On Full Waveform Processing And Positioning Accuracy Optimization Of GF-7 Satellite Borne Laser Altimetry Data

Gaofen-7,China's first civil sub meter scale stereo mapping satellite,was successfully launched in November 2019 and officially put into operation in August2020.As an optical transmission type stereo mapping satellite,GF-7 not only carries a dual-line array stereoscopic mapping camera that can obtain sub meter resolution optical images,but also carries the first satellite borne laser altimeter officially used for earth observation in China.Using the stereo camera with a certain intersection angle,GF-7 can obtain the same orbit optical stereo image of the object by observing from different angles.With the help of its onboard laser altimeter,GF-7 can achieve the ground ranging accuracy of 0.3 meters,so as to obtain high-precision laser altimeter data.With the help of laser elevation points,the target positioning elevation accuracy of GF-7 optical stereo image in the area without ground control has been greatly improved,which meets the requirements of civil 1:10000 scale satellite image topographic mapping.The successful launch and application of GF-7 is of great significance to improve the self-sufficiency rate of China's high-resolution mapping satellite images and enhance China's international influence in aerospace.This article aims to improve the screening effectiveness and positioning accuracy of the GF-7 satellite-borne laser altimetry data,and conducts research on the waveform processing and positioning methods of the GF-7 satellite-borne laser altimetry.Based on the comprehensive analysis of the signal transmission process,waveform characteristics and positioning principles,this article studies studies GF-7 full waveform screening in flat terrain area In addition,the algorithm of satellite laser foot positioning geometric model construction and positioning accuracy optimization.Finally,the validity and reliability of this method are verified by using the measured data.The main research contents of this paper are as follows.1.Based on the imaging principle and geometric positioning model of spaceborne laser altimetry data,this paper analyzes the influence of installation error,pointing angle error,atmospheric delay,tidal error,topographic relief and optical aberration on the accuracy of GF-7 spaceborne laser altimetry data,and gives the corresponding error correction methods.2.By analyzing the characteristics of the full waveform data of the satellite-borne laser altimetry,we propose a fusion peak screening method based on the symmetry of the Gaussian function to eliminate the echo data of the Gaofen-7 satellite-borne laser altimetry.According to the peak threshold and the number of peak points of the waveform,the data of multiple peaks is directly eliminated,and the position of the fused peak is quickly located by calculating the difference between the areas on the left and right sides of the maximum peak point.Through the above calculations,this trticle can accurately extract the laser height measurement data of flat terrain areas,taking into account the efficiency and accuracy of waveform data processing.3.The geometric positioning model of space borne laser altimetry data is proposed,and the corner coordinate positioning accuracy optimization algorithm considering atmospheric delay and tidal effect is realized.