Accurate underwater localization using LBL positioning system

The absolute position of an underwater target is difficult to pinpoint because the global positioning system (GPS) cannot penetrate water bodies. The long baseline (LBL) positioning system can extend GPS using high-precision calibrated underwater beacons as references. While traditional LBL systems give the target position without considering calibration error of deployed beacons. To solve this problem, we propose a method different from previous works, that combining all of the observations together. We use GPS outputs as true values to evaluate the localization performance. An LBL system with four beacons was installed in shallow water and deep sea to test the results. The positioning accuracy in shallow water and deep sea improves 0.06 m and 1.98 m respectively. The results suggest that beacon positioning errors have a great impact on localization precision, especially in deep sea, that is significant in high-precision positioning tasks.