Abstract
In a deep-tow system, the real-time altitude of the tow body above the sea bottom was monitored by using a pinger attached to the tow body and a PDR (Precision Depth Recorder) on a vesssel. This allows even an off-line deep-tow system to operate safely and to keep appointed altitude. The altitude of the tow body above the sea bottom can be calculated from three data: time difference between direct arrival and bottom reflection sound wave sent from the pinger, the length of towing wire, and the inclination angle of the towing wire. Sufficient altitude data for on-board monitoring was obtained by the above calculation.
Field experiments of the altitude monitoring were carried out in four areas of the Pacific side of Japan in water depths between approximately 2,000 m and 7,000 m. In every experiment, the altitude of the tow body above the sea bottom was successfully measured.
