Keywords : multibeam, sounders

Multibeam Sounders

Overview

To explore the seabed, Ifremer uses multibeam sounders

These acoustic systems enable the following to be achieved accurately and rapidly:

  • topographical plotting of the submarine relief (bathymetry),
  • sonar images, showing the local reflectivity of the seabed and thus its nature (imaging).

A multibeam sounder simultaneously measures depth in several directions, determined by the system's reception beams. These beams form a swathe perpendicular to the ship's axis The seabed is thereby explored in a wide band (of around 5 to 7 times the depth), with a very high resolution.

The crossed beam technique

The majority of multibeam sounders use the so-called crossed beam technique.

A sound impulse is emitted through a transmitting lobe, which is narrow in the longitudinal direction (of the order of 1 to 5 degrees) and wide in the transverse direction (typically 150 degrees).

Narrow beams in the transverse plane are used for reception (of around 1 to 5 degrees).

For each reception beam, the area of the seabed explored (the ""ensonified area") is the intersection between the transmitting lobe and the reception beam.