Underwater acoustic source localization and vehicle navigation with two hydrophones

Abstract

Navigation in an underwater environment is challenging because the global positioning system (GPS) is not available owing to the rapid attenuation of electromagnetic waves in water. Acoustic baseline systems are good alternatives to GPS for correcting dead-reckoning errors. However, their deployment and recovery generally require much time and effort. This paper presents a relative navigation approach with a single beacon and an array of two hydrophones in the context of a simultaneous localization and mapping (SLAM) algorithm that can be applied to low-cost unmanned underwater vehicles (UUVs). A stationary sound source is employed as a landmark beacon and its position is estimated using the time difference of arrival (TDOA) measurements provided by hydrophones. However, TDOA estimation is challenging in an actual environment where noise is present. This research proposes a robust time delay estimation algorithm for pure tone acoustic beacon signals. Further, a pair of hydrophones provides a single TDOA measurement, which cannot provide a relative position at a specific time and has ambiguity. To demonstrate and evaluate the effectiveness of the proposed methodology, a field experiment was conducted and the results are presented.