Ruler in Water: 6-DOF Underwater Rotating Platform Calibration for Laser Scanner

Underwater actuated laser scanner, where a structured optical sensor is integrated with a rotating mechanism to scan the underwater target instead of a single line, has been widely applied in underwater resource exploration and biological surveys due to its significance. However, 1) most existing methods cannot be directly applied to underwater scenarios, due to the inconsistency between the center of rotation of the laser scanner and the actuating mechanism. 2) underwater multi-layer medium refraction affects the precision of the underwater camera pose estimation, which further leads to low-precision rotating platform calibration results. To address these challenges, we propose a 6-degree-of-freedom (6-DOF) underwater rotating platform calibration method, named 6DURPC, which can estimate six parameters between the two centers of a structured optical sensor and a rotation platform. Specifically, we first propose a refractive camera model to calculate the pose of camera in water. An underwater rotation platform calibration method is then developed to achieve 6-DOF parameter estimation of camera center and rotation center. To the end, we implement our method on a self-developed underwater laser scanner, and the experimental results in three scenarios demonstrate the performance of our method, and the precision of the reconstructed point cloud reach millimeter level at 2m.