Underwater 3D target detection: Semi-analytic Monte Carlo model and UAV-based scanning lidar system

Lidar has been widely applied in marine research due to its strong penetration capability in water. To study the lidar detection of underwater targets, a semi-Monte Carlo model of target detection (MCT) is developed to simulate the scanning signals, incorporating three-dimensional interaction processes between the beam and the target, the wind-driven surface waves and stratified water columns. A UAV-based linear scanning oceanic lidar system (SOL) is developed for model validation. The model is validated by the lidar equation results with a less than 5% mean relative error within the upper 50 m, and further confirmed by the SOL field experiments through consistent target localization. The detection capabilities of SOL are analyzed based on the MCT model for Jerlov II and Jerlov 3C water types, and an extended detection range is introduced to evaluate the variation of horizontal scanning resolution with target depth, providing guidance for balancing detection capability and efficiency under varying conditions.