A 3D Coherent Laser Imaging Radar Denoising Method Based on the Combination of Intensity and Elevation

Coherent laser imaging radar can obtain high-resolution two-dimensional and three-dimensional imaging results of important targets, and image targets according to the electromagnetic spectrum that is close to human eye observation. Its three-dimensional imaging capability has important application prospects in fine mapping and identification of important targets, obstacle avoidance of unmanned aerial vehicles, low-visibility visual landing and target search, emergency rescue support and other aspects. In May 2023, the first coherent laser imaging radar independently developed by China carried out a flight imaging test in Bayannur, Inner Mongolia, China, and obtained three-dimensional imaging data including urban buildings, Bridges, rails, trains and automobiles, but a large amount of noise in the data seriously affected the recognition of ground objects. To solve this problem, a semi-automatic denoising method based on signal-to-noise segmentation is designed. In this method, the air strips is first sliced according to the fixed number of point clouds, and the point clouds in each slice are projected into the two-dimensional space of "intensity - elevation". Since the intensity value of noise is generally low, it is radiately distributed in the two-dimensional space of "intensity - elevation", that is, the intensity of noise increases slowly with the rise of elevation. Based on this distribution characteristic, the distribution range of noise is judged visually, and the noise is removed by drawing the signal-to-noise dividing line. In the measured data of Bayannur area, the denoising effect of this method is remarkable, and it is obviously superior to the threshold segmentation method using only intensity or elevation, which verifies the effectiveness of this method and lays a foundation for the subsequent application of three-dimensional imaging data of coherent laser imaging radar.