Waveform Processing Of Spaceborne Laser Altimeter And Height Inversion For Multi-mode Target

Spaceborne borne laser altimeter with waveform recording function is a new type of active remote sensing equipment.There is a correspondence between the received pulse echo collected by the spaceborne borne laser altimeter and the geometric characteristic parameters of the target.By processing and analyzing the received pulse echo signal,the geometric information such as the distance,height,inclination and roughness of the target can be retrieved.Therefore,spaceborne borne laser altimetry is widely used in oceanography,ecology,topography,glaciology and other fields,and the development of a universal processing algorithm to receive pulse-echo data is the key to ensure the accuracy of target information retrieval in these fields.At present,the published received waveform data processing method is mainly based on the assumption that the received echo is composed of a mixture of gaussian components.The method of inflection point and nonlinear least square fitting is used to extract waveform parameters.These methods have poor effect on waveform processing of non-gaussian components or components with obvious aliasing.This thesis mainly carried out the following aspects of the research work:(1)Based on the principle of receiving pulse echo signal by satellite-borne laser altimeter,the theoretical expression of multi-mode echo is derived.Through the simulation analysis of echo,the fitting model of echo processing is determined by using the biased normal model;(2)According to the spaceborne borne laser altimeter multimodal distribution characteristics of echo signal.This paper presents an echo data processing algorithm based on layer by layer decomposition of waveform with gradient descent(Waveform Decomposition on Gradient descent-and Levenberg Marquardt,WDGLM);(3)The WDGLM echo data processing algorithm is used to process and analyze the simulated echo data and the actually collected echo data,and the fitting residual and correlation coefficient of the echo are used as the indexes to evaluate the echo processing results.By processing the actual waveform data of a strip,the average values of correlation coefficient and residual were 99.75% and 2.13,are all smaller than the results obtained by the published waveform processing method.At the same time,three sets of aliased original waveforms from the Geoscience Laser Altimeter System are selected.Based on the waveform feature parameters extracted by the waveform processing method in this paper and the height inversion model,the inversion accuracy of the target height is improved by 0.447 m,0.207 m and 0.390 m,respectively.The results show that the WDGLM waveform decomposition method has better universality and higher precision.