UUV localization using acoustic communications, networking, and a priori knowledge of the ocean current

Underwater navigation is particularly challenging due to the fact that a number of navigation aids, such as GPS and similar, are not available. In order to accurately estimate a UUV's position at any time during a mission, we are relying on acoustic communication between the UUV and a network of surface platforms at known locations (reference points). By using the acoustic modems and a model of the environment, the acoustic wave travel time from the UUV to the reference points can be measured and converted into a distance. These distance measurements are then used by a tracking algorithm to improve the UUV positioning accuracy. In previous work [1], a tracking algorithm based on the Unscented Kalman Filter (UKF) was developed presenting satisfactory results. As part of the UUV tracking model, the drift caused by the ocean current was modeled as a random walk and is part of the state of the system. Based on predictions for the ocean current made by different UUVs at different times, a consensus algorithm was developed [2]. The knowledge of the ocean current provided by the consensus algorithm is then used to improve the UUV positioning. The developed algorithms were initially tested using synthetic data. To validate the simulation results, the algorithms were applied to data collected during sea tests that took place in Monterey Bay in August, 2015.