Starborne Photon Counting LiDAR Footprint Location And Accuracy Analysis

With the increasing accuracy requirements of global geolocation services,the need to acquire high-precision 3D data through satellite-based Li DAR is becoming more and more urgent.Therefore,a satellite-based photon counting lidar system with smaller ground footprint points,higher pulse repetition frequency,denser point cloud density,higher number of beams,and higher measurement accuracy has become a research hotspot.On September 15,2018,the United States successfully launched the second-generation ice,cloud,and land elevation satellite ICESat-2,carrying the only currently operating satellite-based photon counting lidar altimetry system in orbit,ATLAS The data conveyed to the ground by the ICESat-2 satellite has been processed and classified into 21 data products by NASA officials.Since the data products were made public,scholars from various countries have conducted a series of researches on the satellite-based photon laser footprint positioning technology,in-orbit calibration technology,and point cloud denoising and classification methods.In this paper,based on ICESat-2 satellite product data as the main data source,combined with airborne laser point cloud data,we investigate the method,solution process and accuracy validation of satellite-based photon counting LIDAR footprint point localization,which are mainly as follows:(1)A geometric model for satellite-based photon counting LIDAR localization is proposed.By analyzing and comparing scholars’ research on laser footprint point localization algorithms for ICESat/GLAS system data and the processing flow,a geometric model of starborne photon counting LIDAR localization applicable to ICESat-2/ATLAS system data is proposed,and a theoretical analysis of the range error sources is conducted,and the nine observational measurement errors in the geometric model are simulated and verified.(2)The correctness of the solution process of laser footprint point location by satellite-based photon counting is verified.Through the study of laser footprint point positioning algorithm and data processing process,the geodetic coordinates of laser footprint points are solved and compared with the geodetic coordinates of corresponding footprint points in ATLAS data product ATL03,and the results show that the root mean square errors of latitude deviation,longitude deviation and elevation deviation are 0.0012″,0.0001″ and0.0469 m respectively,with good accuracy.(3)The effect of laser pointing angle error on the footprint point localization was analyzed.The effects of different laser pointing angle θ and β errors on laser footprint point localization were analyzed using the control variable method,and the results were consistent with the simulation verification errors of laser pointing angle in the geometric model/the accuracy was at the centimeter level with good confidence.(4)Verify the accuracy of the proposed starborne laser footprint positioning method using airborne point cloud data.A single photon point cloud with high confidence is selected and the inverse distance weight interpolation method is used to interpolate the elevation of the starborne laser footprint from the airborne point cloud data with higher accuracy.The comparison analysis between the interpolated elevation and the solved footprint elevation shows that the root mean square error of its calculated elevation difference is 0.4594 m,which proves the effectiveness of the starborne laser footprint localization method.