Acoustic array navigation in shallow water

Abstract

The inversion of acoustic field data for estimation of unknown environmental or geometric parameters is receiving considerable attention. The environmental parameters usually consist of bathymetry, sound speed in the water, and bottom properties such as sound speed, attenuation, and density. The geometric parameters consist of source and array sensor positions. In many situations it is assumed that the array sensor positions are known and in these cases it is important to the inversion process that the array sensor positions are known precisely. In this paper an acoustic navigation method for precisely determining sensor position is presented. Acoustic travel time measurements were used to navigate the sensors of a 94-m vertical array in shallow water (130 m). Array navigation performance was evaluated during a vertical array deployment in the Mediterranean from the R/V Alliance. A network of four bottom-moored acoustic transponders were interrogated from the Alliance and their replies were received by the vertical array sensors and telemetered to the Alliance and their replies were received by the vertical array sensors and telemetered to the Alliance for navigation processing. In October, over a 2-day period, current versus depth and array shape was monitored. During this period the local currents were small; the array shape was estimated to be almost straight and nearly vertical.