Multipath broadband localization, bathymetry, and sediment inversion

Transmission of linearly frequency modulated pulses generates receptions at a vertical line array that can be cross correlated with the source signal to provide estimates of the oceanic waveguide impulse response. For short ranges, distinct path arrivals can be identified including the direct, surface reflection, bottom reflection, and sediment reflection. Accurate estimation of arrival times of such paths is tightly related to successful inversion for source location and water column depth and sound speed and, subsequently, estimation of sediment sound speed and thickness. To achieve accurate estimation, particle filtering is applied to the received time series at 16 phones combined with a simple cross-correlation method. Using linearization, arrival time probability density functions are connected to the geometry and water column sound-speed parameters, providing point estimates as well as probability densities. These are then employed in sediment sound speed and thickness estimation. The results, obtained from the application of the method to data collected during the Seabed Characterization Experiment, are consistent with prior information on the site.