An Original Field Experiment for Positioning of the Seafloor Acoustic Beacon Based on the Ranging Measurement from Surface-Navigation AUV

The Long Base Line (LBL) system is a precise underwater acoustic positioning technique that enables large-scale navigation for multiple unmanned underwater vehicles (UUVs) without surface vessel support. Its performance, however, fundamentally depends on the accurate three-dimensional coordinates of seafloor acoustic beacons, traditionally determined by resource-intensive surface vessel surveys. This study achieves high-precision positioning of seafloor acoustic beacons using ranging measurements from a surface-navigation autonomous underwater vehicle (AUV). By applying the IGG III robust estimation method to two-way travel-time data collected at 2400 m depth in the South China Sea, we accurately determine the absolute coordinates of the seafloor beacons and demonstrate a more cost-effective approach. Furthermore, approximately 40% of the acoustic observation data were missing in the experiment. To address this issue, data simulation processing was conducted. The results show that missing data has an impact on positioning precision. With complete data from simulation, the positioning precision is significantly improved, with the 3D-RMS reduced from 1.817 meters to 1.127 meters, which can meet the requirements for underwater positioning. Collectively, these findings demonstrate that AUVs can serve as a viable and cost-effective alternative to surface vessels for positioning seafloor acoustic beacons, providing a valuable supplementary approach for marine geodetic surveys.