Precise positioning of a transponder placed on a sea floor

A method to determine precisely the position of a transponder placed at a sea floor under a condition that the underwater environment (the sound velocity distribution) is not known, is discussed. If the number of sound rays is taken equal to that of unknown quantities such as the position of the transponder at the sea bottom and the underwater parameters, namely, the sound velocities of layers, the number of equations become equal to that of unknowns. Hence, not only the position of the transponder but also the unknown underwater parameters can be determined at the same time. The effectiveness of the method is verified by numerical calculations.