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Comparative Study on Different Time Discrimination Methods for Full-Waveform Lidar

Full-waveform Light Detection And Ranging (LiDAR) is an active remote sensing technology, in which a laser source emits laser pulses towards objects, and the waveforms of each pair of emitted and returned laser pulses from objects are acquired using a high speed digitizer. Then, the distances between the laser source and the objects are measured based on the acquired waveforms using some time discrimination methods. In this paper, some experiments were carried out to compare and analyze the precisions of five discrimination methods used commonly in full-waveform LiDAR, such as threshold discrimination, constant fraction discrimination, center of gravity discrimination, Gaussian fitting and matched filter discrimination. In experiments, a full-waveform LiDAR system was set up. The waveforms of emitted laser pulses and the waveforms of laser pulses reflected from a Diffuse Reflectance Target (DRT) with 30% reflectivity at distance from 50 m to 110m were obtained using the LiDAR system. Then, the distances between the DRT and the LiDAR system were measured from the waveforms using the five methods. Experimental results show that the precisions of the five methods are positive correlation with the SNR of the waveforms. The threshold discrimination method is of the lowest precision. The matched filter discrimination is of better precision for the waveforms with low SNRs. The center of gravity discrimination and Gaussian fitting are of similar discrimination precision. However, the center of gravity discrimination method is sensitive to sampling start time and sampling length of the laser pulses.