Abstract
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. Not only the position of the transponder but also the unknown underwater parameters can be determined at the same time, if the acoustic rays whose number is equal to or more than that of the unknowns are obtained. The effectiveness of the method is verified by numerical simulations. If only the precise determination of the position of a sea bottom transponder is required, two or three horizontal layers may be sufficient, when a calculation method where underwater sound field is divided into horizontal layers is used.
