Signal Processing for Swath Bathymetry and Concurrent Seafloor Acoustic Imaging.(Reannouncement with New Availability Information)

摘要

Whether they use the multibeam or sidescan geometries, swath bathymetry sonarsystems aspire to provide the widest cross-track coverage with the highest spatial resolution possible. Although these two requirements are often contradictory, a fair compromise can be achieved through a combination of array design and signal processing techniques. To this end, a version of the split-aperture correlator is used in sidescan sonar systems to obtain estimates of differential phase as a function of time of arrival of seafloor echoes. These estimates are subsequently converted to sequences of angle of arrival versus time and then to bathymetry. The same technique is used in beamformed systems to detect the time of arrival of the echoes at the zero crossing of the differential phase sequence. However, this technique is unreliable in the near-specular direction and other beamformed echo detection methods working in the time domain or the spatial frequency domain are considered. FFT beamforming techniques offer some echo detection implementation advantages allowing a choice between any of the aforementioned techniques. For each ping, once signals backscattered by the seafloor have been processed for bathymetry, the magnitudes of the returns can be positioned at their corresponding horizontal distances in an amplitude cross-track profile. Accumulation over many pings of such profiles as lines of a raster image forms a sidescanned acoustic image of the seafloor. This article reviews the signal processing issues related to these echo detection techniques, and their implication for bathymetric resolution and swath coverage....Seafloor swath bathymetry, Bathymetric sidescan sonars, Multibeam echo-sounders, Differential phase estimation.