Fig. 1. Unmanned airborne ocean LiDAR

Fig. 2. Schematic diagram of the receiving optical path

Fig. 3. Photograph of the obstacle

Fig. 4. Multi-channel waveform data obtained by airborne experiment

Fig. 5. Echo energy profile

Fig. 6. Local echo energy profiles of underwater obstacle

Fig. 7. Schematic diagram of the principle of linear-approximation of leading edge algorithm

Fig. 8. Modeling of laser emission angle

Fig. 9. Echo energy profile after angle correction

Fig. 10. Histogram of water surface height statistics

Fig. 11. Local echo energy profile of underwater obstacle after angle correction

Fig. 12. Obstacle echo profile edge extraction results of adjacent scan lines

Fig. 13. Depth of the centroid of obstacle contours

Fig. 14. The 20 sample images used for validating automatic recognition

Fig. 15. Schematic diagram of the water background region extraction