Real-time 3D tracking of whales by echo-robust precise TDOA estimates with a widely-spaced hydrophone array

This paper provides a novel echo-robust and real-time passive underwater acoustic method to track whales using five omni-directional widely-spaced bottom-mounted hydrophones. The interest in online marine mammal monitoring for behavioral studies of endangered species has increased. Practically, these systems are required to be real-time and robust to underwater echoes, which dramatically affect tracking results. To meet these demands, a real-time tracking algorithm was developed with simple but efficient echo cancellation. The processing is all done in the time–domain. After signal decimation, rough time delays of arrival (TDOAs) are calculated, selected and filtered, before precise TDOAs are re-estimated on the original signals. The complete algorithm is tested on real data from the Naval Undersea Warfare Center and the Atlantic Undersea Test & Evaluation Center—Bahamas. The attractive advantage of the method is that it runs two times faster than real-time, but generates similar tracks to other state-of-the-art methods.