Precise Underwater Autonomous Vehicle Localization and Tracking in Unknown Areas with Sound Speed Variation

Xiaolin Liang, Ning Liu, Feng Yang, Lianghui Ding, Liang Qian

Abstract:	Precise localization is crucial for missions such as safety monitoring, mine hunting, glider navigation, marine mammals tracking, etc. To obtain meaningful data from autonomous underwater vehicles (AUV) in an underwater sensor network, we must have precise underwater localization and tracking algorithms. In most range-based underwater localization methods, measurements of time of arrivals (TOA) or time difference of arrivals (TDoAs) are converted into ranges and later incorporated into multi-lateration algorithms. Existing localization algorithms assume the sound speed is constant and the propagation path is a straight line. However, sound speed varies with temperature, pressure, and salinity, causing the bend of underwater sound propagation. Therefore, even if perfect underwater time synchronization exists and TOA or TDoA measurements can be obtained, the localization performance is still degraded by the wrong assumption model. We propose a novel precise underwater localization (PUL) method that addresses the issue of sound speed variation and provides accurate localization and tracking results in unknown underwater environment. In our localization scheme, we employ a real-time effective sound speed and use stochastic filtering to smooth the localization estimation. Effective sound speed is calculated after gathering the pairwise TDoAs, which is incorporated into the localization algorithm. We implement Kalman filter in the localization process to improve localization performance and provide reliable localization. Simulations on PUL and Least Mean Square (LMS) based localization method with variant measurement noise and localization intervals are provided. According to the simulation results, 50% less localization error can be achieved by precise sound propagation model compared with the one with less accurate propagation model.
Published in:	Proceedings of the 2013 International Technical Meeting of The Institute of Navigation January 29 - 27, 2013 Catamaran Resort Hotel San Diego, California
Pages:	386 - 391
Cite this article:	Liang, Xiaolin, Liu, Ning, Yang, Feng, Ding, Lianghui, Qian, Liang, "Precise Underwater Autonomous Vehicle Localization and Tracking in Unknown Areas with Sound Speed Variation," Proceedings of the 2013 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2013, pp. 386-391.
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