MBES

MBES stands for multi-beam echo sounder, a hydrographic instrument used to map seafloor topography. It emits a fan-shaped group of acoustic beams from a transducer array to insonify a wide swath in front of a vessel. By recording the travel time of each beam and its angle, the depth at every beam footprint is calculated. Modern systems form hundreds of beams per ping and rely on precise motion (pitch, roll, heave) and vessel position to locate each depth measurement on the seafloor. The acoustic signal travels through the water column with varying speed, so a sound velocity profile is used to correct beam range and refraction effects. Calibration, motion sensing, and careful SVP and system calibration are essential for accuracy.

MBES systems can be hull-mounted, mounted on a pole, or towed. They typically integrate a dedicated motion reference unit or inertial navigation system and GPS for accurate positioning. Data are processed to produce high-resolution bathymetric digital elevation models and nautical charts. In addition to depth, MBES can provide acoustic backscatter information, aiding seabed classification and habitat mapping. MBES is widely used in hydrographic surveying, offshore engineering, dredging, and environmental studies, enabling efficient mapping of large seabed areas compared with single-beam echo sounding.

Limitations include dependence on stable SVP, vessel motion disturbances, and the need for post-processing; performance can be affected by water depth, seabed properties, and acoustic noise. The technology originated in the late 20th century and has become standard in modern seafloor mapping.