From Light to Position: An Underwater Visual–Inertial Positioning Method Using Visible Light

Reliable localization is essential for the efficiency and safety of autonomous underwater operations. In this study, we propose a novel localization framework centered on a strapdown inertial navigation system, which receives high-precision pose corrections from image-based visible-light positioning. A structured LED array is deployed as a stable underwater positioning reference, and an adaptive optical signal processing method is developed to enhance the extraction of light spot features under challenging scenarios. To address the distortions introduced by cross-medium refraction, we introduce a compensation model that restores accurate camera pose estimation without the need for cumbersome recalibration. Extensive experimental evaluations demonstrate that the proposed system achieves millimeter-level accuracy under favorable scenarios and maintains centimeter-level robustness in unfavorable observation scenarios. Owing to its high-precision, robustness, and cost-effectiveness, the proposed approach holds significant promise for advancing autonomous underwater navigation and next-generation intelligent robotic systems.