Fig. 1. Transmission and scattering of photon packet

Fig. 2. Flow chart of Monte Carlo algorithm

Fig. 3. Airbone double frequency ocean lidar

Fig. 4. Scanning mode of LADMⅡ system

Fig. 5. Relationship between energy and depth of echo wave

Fig. 6. Relationship between pulse width and depth of echo wave

Fig. 7. Matched filtering

Fig. 8. Results of matched filtering and adaptive depth extraction algorithm in deep area under different depths. (a) 33.22 m; (b) 33.64 m; (c) 34.57 m; (d) 33.67 m

Fig. 9. Depth statistics of lidar data

Fig. 10. Comparison of extraction capacity with different methods

Fig. 11. Point cloud of surveying area. (a) Fixed matching filtering algorithm; (b) adaptive depth extraction algorithm

Fig. 12. Single beam sonar data

Fig. 13. Location unmatch between single beam sonar data and lidar data