Passive localization of surface vessels in shallow water using broadband, unintentionally radiated noise

Abstract

The waveguide invariant relates ocean waveguide propagation conditions to the spectral interference patterns (or striations) in range-frequency plots. The striations are the result of interaction between propagating modes. A method of source localization, using a horizontal line array (HLA), that exploits this relationship will be presented. Source azimuth is estimated using conventional Bartlett beamforming, after which source range is estimated from spectral interference observed along the HLA as well as knowledge of the waveguide invariant. Automation of this process makes use of a spectral characterization method for striation slope estimation, which works well in some but not all cases. The use of a physics-based, range-dependent waveguide invariant model to improve the range estimates will also be discussed. This method has been applied to acoustical data recorded in 2007 at the Acoustical Observatory off the coast of Port of the Everglades, Florida. Localization results compare favorably with radar-based Automatic Identification System (AIS) records. [Work supported by ONR Undersea Signal Processing.]