Application of soft constraints on mirror position to improve robustness of optical target positioning in shallow water

The unique optical characteristics of the underwater environment, such as light refraction and loss of salient features, pose a significant challenge to traditional vision sensors, especially in the swarm operation scenario where multiple autonomous underwater vehicles (AUVs) cooperate with the mother ship for positioning. To address these challenges, this study proposes the application of soft constraints on mirror position to improve the robustness of optical target positioning in shallow water. During the mapping phase, we establish and optimize the pose relationships between ArUco markers and their mirrors, thereby expanding the locatable space for AUVs (Autonomous Underwater Vehicles). With the arrangement of ArUco markers unchanged, the number of usable markers doubles. Surface mirror-assisted positioning provides more visual features and additional computed corner points, enhancing the reliability of camera observations and improving positioning accuracy. Experimental results demonstrate that, compared to classical algorithms from the Artificial Vision Applications (A.V.A) laboratory, our method improves position accuracy by 25.8% in single-marker scenarios and by 14.7% in multi-marker scenarios. Therefore, our method provides enhanced mapping and positioning for AUVs in shallow water areas where optical markers can be deployed. This study provides a new mapping paradigm and multi-body localization solution for optical marker-guided underwater swarm operations.