Extracting bottom information from towed-array reverberation data: Part I: Measurement methodology

Abstract

Long-range reverberation data were gathered on towed arrays during the NATO Rapid Response exercises (1996–1998) and the Boundary Characterization experiments (2000–2004). The primary tools were various SACLANTCEN/NURC arrays towed by the NATO Research Vessel Alliance. Most of the sites were in the Mediterranean, in both deep and shallow water, but there were sites on the east and west Atlantic continental shelves. This paper describes the experimental measurements, data processing, and quick-look analyses that were used in our REA (rapid environmental assessment) approach. Polar plots of the beam time series, overlaid on the bathymetry of the region, were extremely useful in providing an immediate analysis of the area. The reverberation highlights are usually correlated with bottom bathymetry and known scattering features. However, it was found that the polar plots often showed scattering features not on the charts, but which could often be identified by detailed follow-on bottom surveys. Thus the polar-plot technique is a valuable survey tool. Examples from a number of the sites are illustrated. The reverberation beam time series data, from areas with few scattering features, were used with model predictions to extract estimates of bottom loss and backscattering strength. An example is given here, but details of the modelling procedure and parameter extraction are left to a companion paper. [Work supported in part by the US Office of Naval Research, DRDC Atlantic and NATO SACLANTCEN/NURC].