Light detection and ranging (LIDAR) is an active remote sensing system. Lidar echo signal is non-linear and non-stationary, which is often accompanied by various noises. In order to filter out the noise and extract valid signal information, a suitable method should be chosen for noise reduction. Some denoising methods are commonly used, such as the wavelet transform (WT), the empirical mode decomposition (EMD), the variational mode decomposition (VMD), and their improved algorithms. In this paper, a new denoising method named the WT-VMD joint algorithm based on the sparrow search algorithm (SSA), for lidar signal is selected by comparative experiment analysis. It is shown that this method is the most suitable one with the maximum signal-to-noise ratio (SNR), the minimum root-mean-square error (RMSE), and a relatively small indicator of smoothness when it is used in three kinds (50, 100, and 1000 pulses) of simulate lidar signals. The SNR is increased by 138.5%, 77.8% and 42.8% and the RMSE is decreased by 81.8%, 72.0% and 68.8% when being used to the three kinds of cumulative signal without pollution. Then, the SNR is increased by 83.3%, 60.4% and 24.0% and the RMSE is decreased by 70.8%, 66.0% and 50.5% when being used to the three kinds of cumulative signal with aerosol and clouds. The WT-VMD joint algorithm based on SSA is used in the denoising process for the actual lidar signal, showing extraordinary denoising effect and will improve the inversion accuracy of the lidar signal.

中文翻译：

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WT-VMD联合算法的激光雷达信号去噪新方法

光探测和测距 (LIDAR) 是一种有源遥感系统。激光雷达回波信号是非线性、非平稳的，往往伴随着各种噪声。为了滤除噪声并提取有效信号信息，应选择合适的降噪方法。常用的去噪方法有小波变换（WT）、经验模态分解（EMD）、变分模态分解（VMD）及其改进算法。本文通过对比实验分析选择了一种基于麻雀搜索算法（SSA）的激光雷达信号去噪新方法，即WT-VMD联合算法。结果表明，该方法是最合适的一种，具有最大信噪比 (SNR)、最小均方根误差 (RMSE)、当用于三种（50、100 和 1000 脉冲）模拟激光雷达信号时，是一个相对较小的平滑度指标。对三种无污染累积信号使用后，信噪比分别提高了138.5%、77.8%和42.8%，均方根误差分别降低了81.8%、72.0%和68.8%。对气溶胶和云的三种累积信号，信噪比分别提高了83.3%、60.4%和24.0%，均方根误差降低了70.8%、66.0%和50.5%。基于SSA的WT-VMD联合算法用于实际激光雷达信号的去噪处理，具有非凡的去噪效果，将提高激光雷达信号的反演精度。8%、72.0%、68.8% 用于三种累积信号无污染。对气溶胶和云的三种累积信号，信噪比分别提高了83.3%、60.4%和24.0%，均方根误差降低了70.8%、66.0%和50.5%。基于SSA的WT-VMD联合算法用于实际激光雷达信号的去噪处理，具有非凡的去噪效果，将提高激光雷达信号的反演精度。8%、72.0%、68.8% 用于三种累积信号无污染。对气溶胶和云的三种累积信号，信噪比分别提高了83.3%、60.4%和24.0%，均方根误差降低了70.8%、66.0%和50.5%。基于SSA的WT-VMD联合算法用于实际激光雷达信号的去噪处理，具有非凡的去噪效果，将提高激光雷达信号的反演精度。