S. E. Dosso
J. M. Ozard
Defence Res. Establishment, Pacific FMO Victoria, BC V0S 1B0, Canada
Ocean-bottom properties such as bathymetry and bottom sound speed can be difficult to measure directly in ice-covered Arctic waters, particularly if they vary with range. However, inversion procedures hold much promise for determining range-dependent bottom properties from acoustic measurements. The inversion is formulated as an optimization problem by assuming a discrete model of unknown parameters and a bounded search space for each parameter. The optimization then involves finding the set of parameter values which minimizes the mismatch between the measured and modeled acoustic fields. Two practical problems are considered. The first problem involves determining range-dependent bathymetry and bottom sound speed using a number of sources at known ranges. The second problem involves source localization when available knowledge of the bathymetry is inadequate. In this case, the inversion is carried out for source range and depth as well as bathymetry. Although the bathymetry cannot be determined uniquely in this manner, an effective bathymetry model can be computed which allows accurate source localization. This latter case is essentially an extension of the method of ``focalization'' [M. D. Collins and W. A. Kuperman, J. Acoust. Soc. Am. 90, 1410--1422 (1991)] to bottom parameters.