Lidar bathymetry over 140 m with polarization noise suppression

Abstract Lidar provides unique capabilities for integrated land-sea surveying, delivering highly efficient and accurate bathymetric and topographic measurements. However, depth challenges remain for existing lidar systems due to the weak signal of water bottom and interference from background noise. Here, we demonstrate, to the best of our knowledge, the deepest detectable depth over 140 m ever reported through lidar bathymetry in the South China Sea. Through a comprehensive lidar emulator, key system parameters were optimized to enhance the bottom signal with a 486 nm laser. Additionally, the emulator formulated the polarization detection to suppress the background noise including dark counts and water column backscatter, owing to their polarized differences from bottom signals. Experimental results demonstrated that the SNR enhancement of cross-polarized signals is 1.6 times that of the total signals at depths exceeding 100 m. Meanwhile, 68.7% of the background noise was suppressed by utilization of the cross-polarized channel. The lidar bathymetric data after multiple scattering corrections showed good agreement with shipborne Acoustic Doppler Current Profiler measurements, with a root mean square relative deviation (RMSRD) of 5.23%. The research offers implications for filling knowledge gaps across continental shelves and delivers new insights for improving seafloor monitoring and benthic mapping.