3D spatial sampling with a cylindrical multibeam sonar array

Abstract

Various beam pair combinations can be formed with cylindrical multibeam sonar arrays to obtain a 3D spatial sampling of a patch of seafloor for each ping. This capability is explored with a 286 deg sector cylindrical array transmitting a stepped FM pulse over a 243 deg vertical fan beam centered on nadir and receiving with twenty-seven beam pairs, symmetrically steered about nadir in the fore-aft direction and spaced at 7.16 deg intervals across track. Conventional conjugate product techniques yield two across-track profiles of 26 soundings each (52 phasors total) per ping. However, by combining one or two phasors along-track and one, two or three phasors across-track, soundings can be obtained at the spatial bisectors of the angles between the 52 phasors. This yields three profiles consisting of 51 soundings each, for a total of 153 soundings. This effectively creates a 3D patch of detected seafloor for each ping, which may overlap with the patches from adjacent pings depending on the sonars attitude changes and altitude above the seafloor. [Work supported by NRL-SSC grant N00173-00-1-G912 and NOAA grant NA170G228.]

Bearing Estimation Uncertainties for the Volume Search Sonar

“…Soc. Am., 117(4-2), 2447, 2005 Various beam pair combinations can be formed with cylindrical multibeam sonar arrays to obtain a 3D spatial sampling of a patch of seafloor for each ping. This capability is explored with a 286º sector cylindrical array transmitting a stepped FM pulse over a 243º vertical fan beam centered on nadir and receiving with twentyseven beam pairs, symmetrically steered about nadir in the fore-aft direction and spaced at 7.16º intervals across track.…”

“…27 fore-aft beam pairs are formed with 27 sub-arrays of 16 contiguous staves. Previous work (Brogan and de Moustier, 2005;2006) has shown that time and angles of arrival of seafloor echoes received at the VSS array can be used to obtain swath bathymetry and seafloor acoustic backscatter imagery. This report is a preliminary analysis of the uncertainties in estimation of the angles of arrival of bottom echoes received by pairs of VSS beams.…”

“…VSS ping 3897 -Soundings (dots) obtained for one ping and corresponding bathymetry patch. Color bar is depth in meters(Brogan and de Moustier, 2005) Fig. 3 Triangular Irregular Network (TIN) of (a) one swath of VSS bathymetry (color bar in meters) (a) and (b) locally normalized seafloor acoustic backscatter intensity (grey scale bar in dB) (Brogan and de Moustier, 2005)…”