multibeamsonars

Multibeam sonars are hydrographic surveying systems that emit a fan of acoustic beams from a transducer array to map the seafloor. By generating many beams simultaneously, they cover a wide swath across the vessel’s track, providing higher-resolution bathymetry than single-beam sonars. Depth at each beam is calculated from travel time and beam angle, with corrections for vessel motion. Multibeam systems are typically hull-mounted or towed, and are also used on autonomous underwater vehicles.

Operation spans a range of frequencies, commonly from tens to a few hundred kilohertz, chosen for depth and resolution. Swath width depends on beam angle, depth, and height above the seabed. Outputs include bathymetric point data and often backscatter maps that assist bottom typing. Accurate depth measurements require motion compensation, sound velocity profiling, and precise positioning; data are later processed into gridded digital elevation models through filtering, gridding, and QA/QC.

Applications include hydrographic charting, offshore construction surveys, dredging planning, environmental monitoring, and underwater archaeology. Compared with single-beam sonar, multibeam systems provide faster coverage and higher-resolution maps but generate large data volumes and demand substantial processing. Limitations include shadowing behind features, bottom type effects, and sensitivity to sound velocity changes and calibration.