multibeam

Multibeam is a class of sonar systems used to map the seafloor by emitting multiple acoustic beams from a single transducer array. Multibeam systems, commonly multibeam echosounders, provide broad swath coverage and higher data density than single-beam instruments and are widely used in hydrographic surveying, marine construction, offshore energy, and coastal mapping.

Principle of operation: A phased or mechanical array emits a fan of beams across the survey swath. Travel times and beam angles are recorded to compute depth for many points in a single ping. Depth calculations rely on accurate sound velocity profiling in the water column and are corrected for vessel motion—pitch, roll, heading, and heave—as well as tide and datum shifts.

Processing and outputs: Raw beam measurements are filtered, corrected, and gridded to form a bathymetric surface. Quality control and post-processing remove spurious returns and apply tidal and SVP corrections. The results are used to generate bathymetric charts, digital elevation models, and seabed classifications, often referenced to standard nautical datums.

Applications and advantages: Multibeam enables rapid, high-resolution mapping of complex seabeds, shorelines, and nearshore zones, supporting navigation safety, dredging planning, offshore construction, and habitat studies. It offers higher coverage efficiency and better edge performance than single-beam systems, but requires more elaborate data processing, accurate SVP, motion sensing, and calibration; performance can be challenged by rough seas, weak bottom returns, or high glare from soft sediments.

History and notes: Since the 1980s, multibeam technology has advanced with improvements in transducer design, signal processing, and motion compensation, leading to routine use in modern hydrographic surveys. Data collected by multibeam are typically managed under international hydrographic standards and integrated into national nautical charts.