Underwater Acoustic Pulsed Source Localization with a Pair of Hydrophones

Abstract

A series of underwater acoustic localization experiments were conducted in the Eastern Mediterranean Sea to test the performance of a Bayesian method for localization of pulsed acoustic sources exploiting time differences between direct and surface-reflected arrivals at two hydrophones of known depth. The experiments involved a controlled source (pinger) at various depths/ranges as well as vocalizing sperm whales encountered off southern Crete. The localization method provides primarily range and depth information. In addition, if the location of the hydrophones in the horizontal is known, horizontal localization can be performed as well, subject to left–right ambiguity; this was applied for whale localization. The localization results confirmed the anticipated behavior of range, depth, and bearing estimation errors, which, according to theory, depend mainly on the source azimuth. In particular, range and depth estimation errors are larger for source locations close to broadside to the array and smaller towards endfire, and they increase with range. Conversely, bearing estimation errors are larger close to endfire and smaller towards broadside. Localizations in this paper were performed to ranges of about 3.5 km. The limiting factors for localization to longer ranges were the loss of ability to resolve direct and surface-reflected arrivals as well as the self-noise of the hydrophones.

Underwater Acoustic Location Estimation of Flight Recorder Using Onboard Ad Hoc Wireless Sensor Network

“…It uses historic information to increase localization precision and it filters out outliers. Skarsoulis et al [33] propose a localization method using a pair of spherical piezoelectric hydrophones towed under a marine vessel. Their approach is tested in the Eastern Mediterranean Sea off the north and south coast of Crete, in shallow and deep water respectively.…”

A Direction-of-Arrival Estimation Algorithm Based on Compressed Sensing and Density-Based Spatial Clustering and Its Application in Signal Processing of MEMS Vector Hydrophone

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“…Direction of arrival (DOA) estimation has been an important research field for scientific researchers because of its wide application scenarios. Its application in 5G and internet of things communication [ 1 , 2 ], medical imaging [ 3 ], earthquake monitoring [ 4 ] and underwater acoustic signal processing [ 5 , 6 ] greatly facilitates people’s production and life. With the rapid development of information technology, more and more application scenarios and complex application environment bring more challenges to DOA estimation technology.…”

A Real-Time Acoustic Observatory for Sperm-Whale Localization in the Eastern Mediterranean Sea

“…3D localization based on direct and surface-reflected arrivals was originally introduced in connection with receptions at two hydrophones separated in the horizontal, e.g. two-hydrophone towed arrays, first assuming homogeneous environments (Skarsoulis et al, 2004;Thode, 2004) and then generalizing for refractive environments using ray-theoretic approaches (Skarsoulis and Kalogerakis, 2005;Thode, 2005;Skarsoulis and Kalogerakis, 2006;Skarsoulis and Dosso, 2015). In those approaches source range and depth estimation only requires knowledge of hydrophone depths, not their location in the horizontal; if the latter is also known, then the source azimuth can be estimated too.…”

“…In those approaches source range and depth estimation only requires knowledge of hydrophone depths, not their location in the horizontal; if the latter is also known, then the source azimuth can be estimated too. This method was tested in the field, in a series of controlled localization experiments as well as for the localization of sperm whales using large-aperture towed two-hydrophone arrays (Thode, 2004;Thode, 2005;Skarsoulis et al, 2018). Two-hydrophone localization is subject to left-right ambiguity, and localization uncertainties are subject to angular dependence.…”