マルチビーム音響測深機を使った開口合成

概要

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Hydrophone signals obtained by a Sea Beam 2000 system were analyzed using the Synthetic Aperture (SA) technique to obtain a high-resolution profile of seafloor topography. The survey line spans 5 km with a water depth of 500 m to 1,000 m in Sagami Bay. Careful and slow navigation was performed to suppress deflection from the planned survey line. The data taken by 42 hydrophones (half of the hydrophones on the array of the Sea Beam 2000) were recorded for one hour at a 48 kHz sampling rate. Simultaneously, to measure the deflection from the planned line, the roll, pitch, and heading angle of the ship and its positiond determined by Kinematic GPS were recorded. The reference orbit axis of the projector array was obtained first. Each hydrophone signal in the time domain was then corrected by time shifting at each designed beam angle in order to construct multiple received beam forms with no fluctuations on the reference orbit axis. This correction canceled the deviation of the projector array at transmission and the hydrophone when received on each received beam axis from the reference orbit axis. Finally, an SA beam was formed using three-ping and five-ping received beams with no fluctuation on the reference orbit axis. As a result, the resolution of the SA beams increased.
社団法人日本音響学会の論文