The multibeam acoustic sounding system

6. At the end of 1999, the Belgica was fitted with highly technical equipment to carry out depth measurements of the sea floor. This is known as the multibeam acoustic sounding system. This appliance uses acoustic techniques to measure depth profiles in a broad strip beneath the ship. These measurements can be used to produce both high-resolution depth charts and sediment classification charts of the sea floor.

To make the multibeam bathymetric recordings, a transducer attached to the bottom of the ship is stretched out about one meter from beneath the keel with a bar. Using the transducer, 111 acoustic beams (frequencies 93 and 98 kHz) are generated simultaneously up to ten times a second. These multiply through the water and are then reflected by the sea bed and caught again by the transducer elements. The time between the sending of the acoustic signals and the reception of the reflected signals is accurately measured by the multibeam measuring systems and processed, thereby measuring the depth of the sea floor across a broad strip beneath the ship (up to eight times the water depth). A powerful computer is essential to process and store the huge quantity of signals. The water depths that can be measured by the multibeam acoustic sounding system vary from two meters below the keel of the ship to 1000 meters .

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