激光测高仪的回波信号理论模型

Theoretical model for return signal of laser altimeter

利用菲涅尔衍射理论推导出高斯型激光脉冲的回波计算方法,建立了斜坡、阶梯和植被三种标准漫反射地物的回波模型,以GLAS(Geoscience Laser Altimeter System)系统为例,通过数值计算得到了标准漫反射地物的回波信号波形,分析了回波波形与三种地物模型参数、光束扫描角之间的关系。仿真计算结果表明:斜坡回波信号波形近似为单个高斯波形,其峰值和脉宽与斜坡倾角、光束扫描角有关;阶梯回波信号波形近似为多个高斯波形,其峰值与光斑内阶梯分布有关;波形的中心位置差与阶梯高度和光束扫描角有关;植被回波信号波形呈现出多个类高斯型,其峰值不仅与植被的位置有关,还与植被的面积有关。这些结论为地形地貌的反演及地表资源分布的分析提供了理论基础。

A method for calculating return waveform was deduced by the theory of Fresnel diffraction, and the models of return waveform from ground of slope, ladder and vegetation terrains were estibalished. According to the data of Geoscience Laser Altimeter System（GLAS）, the waveforms of correspond return signal were obtained through computing. The relations between the waveforms of return signal and parameters of three terrains, point angle were analyzed. The conclusions show that the return waveform of slope terrain is approximately Gaussian, whose peak value and pulse width are related with slope angle and beam scanning angle; The return waveform of ladder terrain is approximately model of multi-Gaussian, whose peak value is related with ladder distribution in the footprint and simultaneity, the difference between their centers of gravity is concerned with ladder height and scanning angle; The return waveform of vegetation terrains appears multi--Gausssian, whose peak value is not only related with vegetation position, but also its area. These results provide theoretical foundation for inversion of landform and analysis of resource distribution of the earth＇s surface.