Multibeam (or swath) SONAR – a significant advance over side-scan SONAR – employs a multitude of individual SONAR beams to ensonify the seafloor.  Multibeam SONAR systems provide fan-shaped coverage of the seafloor – similar to side-scan SONAR but with different data output.  Where side-scan SONAR continuously records the strength of the return echo (ping), multibeam systems measure and record the time for the acoustic signal to travel from the transducer to the seafloor and back.  Knowing the time, the distance to the seafloor can be calculated; in turn, using the transmission angle from the transducer, the depth at each beam can be determined.  Placing beam points (as many as 512 for some multibeam echo sounders) in a line produces data from which a contour for each ping can be developed; placing these contours side by side allows a three-dimensional representation of the seafloor to be developed.

Multibeam SONAR offers considerable advantages over conventional systems, including increased detail of the seafloor (100 percent coverage), confidence that all features and hazards are mapped without voids, the ability to map inaccessible areas (e.g., under jetties, structures, and vessels near breakwaters, in shoal areas, and adjacent to retaining walls), fewer survey lines (which shortens survey time), optimum seafloor detail for route and dredge programs, and the ability to comply with the highest order International Hydrographic Organization (IHO) and US Army Corps of Engineers (USACE) hydrographic standards.

The multibeam SONAR transducer (multibeam echo sounder) can be mounted on many types of survey platforms, including towfish, ship hulls, and remotely operated vehicles (ROVs).  Substructure regularly uses multibeam SONAR in the field – see how Substructure can put this technology to work for you.

To learn more about another type of SONRA technology, go to Sub-Bottom Profiling.