The Geoclutter experiment: Remotely imaging sub-bottom geomorphology in shallow water

Abstract

Preliminary results of the Geoclutter experiment of April–May 2001 are presented. This bistatic reverberation experiment was conducted at the New Jersey Strataform site in continental shelf waters. Roughly 3000 waveforms were transmitted from vertical source arrays in the 390–440 Hz band and received by a horizontally towed array. On average roughly 10–100 discrete clutter events were registered per transmission for a total of at least 30<th>000 geoclutter events that could be confused with a discrete target over the period of the experiment. Bathymetry throughout the New Jersey Strataform area is extremely benign with few discrete features. The vast majority of clutter returns appeared in level areas where absolutely no bathymetric features are present. The clutter events often registered well with buried river channel networks previously characterized in the Geoclutter program. Extensive probing of river-channel-infested areas revealed that the number and level of clutter events is highly dependent on bistatic orientation. The registrations suggest that bistatic aspects that produce ‘‘glints’’ from large projected areas along river channel axes yield the strongest and most frequent targetlike returns. These results are consistent with those predicted by a unified model for reverberation and submerged-target scattering [J. Acoust. Soc. Am. 109, 909–941 (2001)].