DEPTH MEASUREMENT OF REMOTE SOURCES USING MULTIPATH PROPAGATION

A submerged acoustic source radiates narrowband Gaussian noise. Its si gnal propagates to a remote, large aperture vertical array over a mult ipath channel whose characteristics may or may not be fully known. The primary concern of this paper is the accuracy of source depth estimat es obtainable from the array output. Cramer-Rao bounds for the depth e stimate are calculated. When the velocity profile is known exactly the value of the bound is quite insensitive to the precise form of the ve locity profile. A bound calculated from a constant velocity profile yi elds an excellent approximation for many situations likely to be encou ntered in practice. Introduction of an unknown parameter into the velo city profile has little effect on the Cramer-Rao bound for depth. Howe ver, a maximum likelihood estimator of depth working with an inaccurat e value of the unknown parameter performs poorly. To obtain satisfacto ry performance one must estimate the unknown parameters along with the source depth. Simulations demonstrate the success of this approach.