Fig. 1. Image assembled by stitching waveforms. (a) Example of lidar echo waveform stitching; (b) echo waveform containing surface water, subsurface water, and underwater obstacles; (c) echo waveform containing surface water and subsurface water

Fig. 2. Comparison of images before and after correction. (a) Example of image before correction; (b) example of corrected image

Fig. 3. Comparison of waveforms with and without water scattering removal for the obstacle located in the water scattering region

Fig. 4. Comparisons of contrast in obstacle and background areas before and after water scattering removal. (a) Contrast calculation area in image before water scattering removal; (b) contrast calculation area in image after water scattering removal; (c) contrast between obstacle and background areas before water scattering removal; (d) contrast between obstacle and background areas after water scattering removal

Fig. 5. Comparison before and after replacing local bright stripes. (a) Local image before replacing local bright stripes; (b) local image after replacing local bright stripes; (c) horizontal gradient map before replacing local bright stripes; (d) horizontal gradient map after replacing local bright stripes

Fig. 6. DoG-ECD method process

Fig. 7. Canny operator detection results. (a) Global image; (b) local image

Fig. 8. Experimental results of image processing. (a)(d)(g)(j) Input images; (b)(e)(h)(k) optimal scale corresponding to input images; (c)(f)(i)(l) obstacle area and connected domain labels corresponding to input images