Application of high-resolution beamforming to multibeam swath bathymetry

Abstract

In the context of swath bathymetry with multibeam echo-sounders, seafloor echoes received at regularly spaced elements of a hydrophone array are summed coherently to form a number of directional beams from which athwartships depth measurements are derived. This process can be implemented as a conventional beamformer leading to estimates of the direction of arrival of the echoes for each time sample. The process is inadequate in resolving closely spaced synchronous returns and the accuracy of these estimates is proportional to the number of acoustic data samples used in the process. To improve the angular resolution the authors have considered a number of high-resolution algorithms well known in power spectral estimation applications: autoregressive techniques (i.e. Yule-Walker, and unconstrained least squares), minimum variance methods (i.e. Capon's method), and eigenanalysis algorithms (i.e. MUSIC). Comparisons of results obtained with realistic multibeam sonar simulations show that these algorithms have higher accuracy and better potential for high-resolution bathymetry than the conventional beamformer under nominal SNR levels.<>