Multibeam is an acoustic technique used for the production of bathymetric and sediment classification maps. Different sonar models are classified according to the following parametres:

• acoustic frequency
• depth
• number of beams
• size of beams
• angleof entry of each beam
• rate and duration of pulse

multibeam swath bathymery: seafloor imaging

Bathymetric data for the Geogia Basin were obtained using two models, EM1002 and EM3000, their specifics are as follows:

How does it work?

A transducer emits a signal composed of several straight beams forming a band perpendicular to the ship's axis. This allows for the coverage of a large area over a relatively short period of time. An elevated sonar emission frequency decreases the range, however, it increases the resolution of the data. After a delay, the sonar waves are reverberated from the seafloor and received by the transducer. The depth of the seafloor and the presence of obstacles can be determined by the time elapsed between emission and reception of the signals. The average depths is obtained from the first beam directly beneath the axis of the ship. The exact position of the ship is determined using a GPS, this is important in creating representative bathymetric maps. Also, the rolling, pitching, and heave of the ship must be taken into account. Detectors are used so that the influence these have on the results can be measured.