Comparative studies of wavelet threshold and complementary ensemble empirical mode decomposition in the denoising of differential column image motion lidar
Cheng Zhi, Feng Wei He, Xu Jing, Xiang Yan, Chao Mu · 2017
Differential column image motion lidar (DCIM lidar) can obtain the Fried’s transverse coherence length (r0) of different altitudes with a high spatial and temporal resolution. According to the integral equation of atmospheric coherence length (r0) of spherical wave, the refractive structure constant(C2n) profile can be retrieved from r0 profile. Aiming at improving the retrieval accuracy of atmospheric turbulence profile, noise reduction on r0 profile is implemented before inversion. Two methods of wavelet threshold and complementary ensemble empirical mode decomposition (CEEMD) are used to denoise r0 profile. The effects of denoised methods on r0 profile and C2n profile are investigated. The numeric simulations and experiments are both carried out to validate the two denoised methods. The results show that both the two methods can improve the signal-to-noise ratio (SNR) of atmospheric coherent length profile and reduce the recovered error of the atmospheric turbulence profile, and wavelet threshold method is superior to CEEMD method under different noise conditions.