Directional Correspondence Based Cross-Source Point Cloud Registration for USV-AAV Cooperation in Lentic Environments

We propose a novel cross-source point cloud registration (CSPR) method for USV-AAV cooperation in lentic environments. In the wild outdoors, which is the typical working domain of the USV-AAV team, CSPR faces significant challenges due to platform-domain problems (complex unstructured surroundings and viewing angle difference) in addition to sensor-domain problems (varying density, noise pattern, and scale). These characteristics make large discrepancies in local geometry, causing existing CSPR methods that rely on point-to-point correspondence based on local geometry around key points (e.g. surface normal, shape function, angle) to struggle. To address this challenge, we propose the novel concept of a directional correspondence-based iterative cross-source point cloud registration algorithm. Instead of using point-to-point correspondence under large discrepancies in local geometry, we build correspondence about directions to enable robust registration in the wild outdoors. Also, since the proposed directional correspondence uses bearing angle and normalized coordinate, we can separate scale estimation with transformation, effectively resolving the problem of different scales between two point clouds. Our algorithm outperforms the state-of-the-art methods, achieving an average error of $1.60^\circ$ for rotation and 1.83% for translation. Additionally, we demonstrated a USV-AAV team operation with enhanced visual information achieved with the proposed method.