Passive acoustic source depth discrimination with two hydrophones in shallow water

It is important for sonar systems to distinguish the submerged source from the surface one. Current approaches based on matched field processing, mode scintillation and mode filtering require either precise knowledge of the ocean environment parameters or densely populated hydrophone arrays, and become problematic in practical use. Current waveguide invariant based method, deriving the distribution of the waveguide invariant from the LOFAR diagram using standard Radon transform or standard Hough transform, will have a large error variance when the interference striation is break off or intersect with each other, resulting in a bad performance. This paper proposed a new method of source depth discrimination which uses the local angle of the interference striations directly from the LOFAR diagram with the help of two dimensional discrete Fourier transform. The method analyzes the existing LOFAR diagram and needs no prior information of the ocean environment. It is more robust and computation efficient because of the accumulate effect and the use of FFT.