利用自适应滤波星载激光测高仪回波噪声抑制方法

Noise suppression method for received waveform of satellite laser altimeter based on adaptive filter

具有波形记录功能的星载激光测高仪,通过回波信息解算地表与卫星平台距离和反演地物特性。目前广泛采用的固定宽度高斯滤波方法在抑制回波噪声过程中造成有效信号变形,对提取信号有效参量造成严重干扰。根据分块信号统计特性不同的规律,提出了激光测高仪回波噪声均值和方差的估计方法;根据回波信号的统计特性,设计了一种宽度自适应的高斯滤波器。通过GLAS系统实测回波信号的噪声估计与自适应高斯滤波、高斯拟合,得到的波形处理结果与GLAS官方数据有很好的吻合度,噪声均值估计误差小于0.4个数字化仪单位,有效高斯参数计算误差小于1%。该方法能准确地提取波形参量,为地表高程解算和目标表面信息反演提供有效数据。

For satellite laser altimeter, the range between earth surface and satellite platform could be calculated, and the target characters could be inversed through extracting the parameters of received waveforms. The signal degradations emerge on the noise suppression process of returned pulse using the fixed width Gaussian filter, which influences seriously the extracting of the effective parameters. Based on the different statistical regularities among blocked signal, a new method is presented to estimate the mean and standard deviation of returned waveforms, and a width adaptive Gaussian filter is designed according to the statistical characters of returned pulse. The received digital counts data of GLAS were used to the Noise estimation, adaptive Gaussian filter, and Gaussian fitting were measured by GLAS system. The calculation results accord with GLAS official statstics. The errors of estimated noise mean were less than 0.4 digitized unit, and the effective Gaussian parameter errors are less than 1%. The conclusion is that the returned pulse parameters of laser altimeter could be extracted effectively and accurately through this noise suppression method.