Hubbry Logo
Multibeam echosounderMultibeam echosounderMain
Open search
Multibeam echosounder
Community hub
Multibeam echosounder
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Multibeam echosounder
Multibeam echosounder
Multibeam echosounder
View on Wikipedia
from Wikipedia
Multibeam sonar is used to map the ocean floor

A multibeam echosounder (MBES) is a type of sonar that is used to map the seabed. It emits acoustic waves in a fan shape beneath its transceiver. The time it takes for the sound waves to reflect off the seabed and return to the receiver is used to calculate the water depth. Unlike other sonars and echo sounders, MBES uses beamforming to extract directional information from the returning soundwaves, producing a swathe of depth soundings from a single ping.

History and progression

[edit]
A multibeam image of the USS Susan B. Anthony (AP-72) shipwreck off the coast of France.

Multibeam sonar sounding systems, also known as swathe (British English) or swath (American English) [citation needed], originated for military applications. The concept originated in a radar system that was intended for the Lockheed U-2 high altitude reconnaissance aircraft, but the project was derailed when the aircraft flown by Gary Powers was brought down by a Soviet missile in May 1960. A proposal for using the "Mills Cross" beamforming technique adapted for use with bottom mapping sonar was made to the US Navy. Data from each ping of the sonar would be automatically processed, making corrections for ship motion and transducer depth sound velocity and refraction effects, but at the time there was insufficient digital data storage capacity, so the data would be converted into a depth contour strip map and stored on continuous film.[1] The Sonar Array Sounding System (SASS) was developed in the early 1960s by the US Navy, in conjunction with General Instrument to map large swathes of the ocean floor to assist the underwater navigation of its submarine force.[1][2] SASS was tested aboard the USS Compass Island (AG-153). The final array system, composed of sixty-one one degree beams with a swathe width of approximately 1.15 times water depth, was then installed on the USNS Bowditch (T-AGS-21), USNS Dutton (T-AGS-22) and USNS Michelson (T-AGS-23).[1]

At the same time, a Narrow Beam Echo Sounder (NBES) using 16 narrow beams was also developed by Harris ASW and installed on the Survey Ships Surveyor, Discoverer and Researcher. This technology would eventually become Sea Beam Only the vertical centre beam data was recorded during surveying operations.[1]

Starting in the 1970s, companies such as General Instrument (now SeaBeam Instruments, part of L3 Klein) in the United States, Krupp Atlas (now Atlas Hydrographic) and Elac Nautik (now part of the Wärtsilä Corporation) in Germany, Simrad (now Kongsberg Discovery) in Norway and RESON now Teledyne RESON A/S in Denmark developed systems that could be mounted to the hull of large ships, as well as on small boats (as technology improved, multibeam echosounders became more compact and lighter, and operating frequencies increased).[citation needed]

The first commercial multibeam is now known as the SeaBeam Classic and was put in service in May 1977[3] on the Australian survey vessel HMAS Cook. This system produced up to 16 beams across a 45-degree arc. The (retronym) term "SeaBeam Classic" was coined after the manufacturer developed newer systems such as the SeaBeam 2000 and the SeaBeam 2112 in the late 1980s.

The second SeaBeam Classic installation was on the French Research Vessel Jean Charcot. The SB Classic arrays on the Charcot were damaged in a grounding and the SeaBeam was replaced with an EM120 in 1991. Although it seems that the original SeaBeam Classic installation was not used much, the others were widely used, and subsequent installations were made on many vessels.[citation needed]

SeaBeam Classic systems were subsequently installed on the US academic research vessels USNS Thomas Washington (T-AGOR-10) (Scripps Institution of Oceanography, University of California), the USNS Robert D. Conrad (Lamont–Doherty Earth Observatory of Columbia University) and the RV Atlantis II (Woods Hole Oceanographic Institution).

In 1989, Atlas Electronics (Bremen, Germany) installed a second-generation deep-sea multibeam called Hydrosweep DS on the German research vessel Meteor. The Hydrosweep DS (HS-DS) produced up to 59 beams across a 90-degree swath, which was a vast improvement and was inherently ice-strengthened. Early HS-DS systems were installed on the RV Meteor (1986) (Germany), the RV Polarstern (Germany), the RV Maurice Ewing (US) and the ORV Sagar Kanya (India) in 1989 and 1990 and subsequently on a number of other vessels including the RV Thomas G. Thompson (US) and RV Hakurei Maru (Japan).[citation needed]

As multibeam acoustic frequencies have increased and the cost of components has decreased, the worldwide number of multibeam swathe systems in operation has increased significantly. The required physical size of an acoustic transducer used to develop multiple high-resolution beams, decreases as the multibeam acoustic frequency increases. Consequently, increases in the operating frequencies of multibeam sonars have resulted in significant decreases in their weight, size and volume characteristics. The older and larger, lower-frequency multibeam sonar systems, that required considerable time and effort mounting them onto a ship's hull, used conventional tonpilz-type transducer elements, which provided a usable bandwidth of approximately 1/3 octave. The newer and smaller, higher-frequency multibeam sonar systems can easily be attached to a survey launch or to a tender vessel. Shallow water multibeam echosounders, like those from Teledyne Odom, R2Sonic and Norbit, which can incorporate sensors for measuring transducer motion and sound speed local to the transducer, are allowing many smaller hydrographic survey companies to move from traditional single beam echosounders to multibeam echosounders. Small low-power multibeam swathe systems are also now suitable for mounting on an Autonomous Underwater Vehicle (AUV) and on an Autonomous Surface Vessel (ASV).[citation needed]

Multibeam echosounder data may include bathymetry, acoustic backscatter, and water column data. (Gas plumes now commonly identified in midwater multibeam data are termed flares.)

Type 1-3 piezo-composite transducer elements,[4] are being employed in a multispectral multibeam echosounder to provide a usable bandwidth that is in excess of 3 octaves. Consequently, multispectral multibeam echosounder surveys are possible with a single sonar system, which during every ping cycle, collects multispectral bathymetry data, multispectral backscatter data, and multispectral water column data in each swathe.[5]

A multibeam echosounder showing the transmit array (larger black rectangle) and receive array (narrower rectangle) - Odom MB1

Modern scientific uses

[edit]

As technology improved in the 1980s and 1990s, higher-frequency systems which provided higher resolution mapping in shallow water were developed, and today such systems are widely used for shallow-water hydrographic surveying in support of navigational charting. Multibeam echosounders are also commonly used for geological and oceanographic research, and since the 1990s for offshore oil and gas exploration and seafloor cable routing. More recently, multibeam echsounders are also used in the renewable energy sector such as offshore windfarms.[6]

Multibeam has allowed oceanographers to work much faster in mapping the seafloor, we've reached a total mapping of 26.1% of the sea floor.[7] This increase in speed has led to a much greater understanding of a wide variety of subjects, mainly climate science and marine biology, also leading to the creation of the seabed 2030 initiative, which is hoping to have the entire seafloor mapped out by 2030[8]

Theory of operation

[edit]

A multibeam echosounder is a device typically used by hydrographic surveyors to determine the depth of water and the nature of the seabed. Most modern systems work by transmitting a broad acoustic fan shaped pulse from a specially designed transducer across the full swathe acrosstrack with a narrow alongtrack then forming multiple receive beams (beamforming) that are much narrower in the acrosstrack (around 1 degree depending on the system). From this narrow beam, a two way travel time of the acoustic pulse is then established utilizing a bottom detection algorithm. If the speed of sound in water is known for the full water column profile, the depth and position of the return signal can be determined from the receive angle and the two-way travel time.

In order to determine the transmit and receive angle of each beam, a multibeam echosounder requires accurate measurement of the motion of the sonar relative to a cartesian coordinate system. The measured values are typically heave, pitch, roll, yaw, and heading.

To compensate for signal loss due to spreading and absorption a time-varied gain circuit is designed into the receiver.

For deep water systems, a steerable transmit beam is required to compensate for pitch. This can also be accomplished with beamforming.

References

[edit]

Further reading

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Multibeam echosounder

View on Grokipedia
from Grokipedia
A multibeam echosounder (MBES) is an active system that emits multiple narrow acoustic beams simultaneously in a fan-shaped from a mounted on a ship's hull, enabling the mapping of large swaths of the seafloor by measuring the time for pulses to return after reflecting off the bottom, thus providing high-resolution bathymetric data across a wide coverage area. Unlike single-beam echosounders, which measure depth only directly beneath the vessel, MBES systems use techniques to steer and focus beams, combining signals from an of transducers to achieve precise depth measurements and intensity for each beam, revealing seafloor composition such as versus soft . The technology relies on the known in to calculate depths, with typical resolutions varying from a few meters in shallow waters to coarser in deeper oceans, and it often integrates with GPS for georeferenced outputs. Developed from military sonar applications, multibeam systems trace their origins to the , when the Mills Cross technique was patented for the U.S. Navy's Array Sounding System (SASS), evolving into commercial tools like the SeaBeam system introduced in the 1970s for civilian hydrographic surveys. Key components include projector arrays for transmitting pings at frequencies typically between 10 kHz and 500 kHz, arrays for receiving echoes, and onboard processing units that apply corrections for sound velocity profiles, vessel motion, and to ensure accuracy. Modern MBES can produce up to 1,000 or more beams per ping; for example, the EM 124 supports up to 1,600 beams, covering swaths up to 5.5 times the water depth, and are calibrated using protocols that account for geometry and environmental factors like and . In practice, MBES data yields both depth soundings for 3D seafloor models and mosaics that highlight geological features, such as reefs or types, supporting applications in , habitat assessment, and . For instance, surveys on the Shelf have used MBES to map benthic habitats at resolutions of 4–8 meters, identifying reef structures and aiding fisheries conservation by distinguishing hard-bottom communities from soft s. These systems also detect water-column anomalies like gas seeps or shipwrecks through , enhancing their utility in and , though challenges like signal in deep reduce resolution in water depths greater than 6,000 meters. Overall, MBES has revolutionized since the late , enabling efficient, wide-area seafloor characterization essential for , offshore , and scientific .

History

Early Development

The development of multibeam echosounders originated in the early as an advancement over single-beam echosounders, motivated by requirements for rapid, wide-area seafloor mapping to support and mine countermeasures during the . The U.S. Navy recognized the limitations of single-beam systems, which provided only a narrow sounding line beneath a vessel, and sought technologies to cover broader swaths for detecting underwater hazards and charting ocean floors efficiently. This effort was spurred by geopolitical tensions, including the 1960 U-2 spy plane incident, which underscored the need for detailed deep-ocean surveys to enhance naval strategic capabilities. Conceptual designs for multibeam systems first appeared in the late 1950s and gained momentum in the early 1960s through U.S. initiatives, including the 1961 Bottom Mapping Sonar (BOMAS) proposal developed by engineers at the Harris Anti-Submarine Warfare (ASW) division. Early prototypes employed linear arrays to generate multiple fixed beams simultaneously, evolving from earlier mechanically steered single-beam approaches to enable contiguous sounding coverage. The pioneering operational system, the Sonar Array Sounding System (SASS), was prototyped and tested in 1963 aboard the USS Compass Island by Corporation in collaboration with the . By 1965, SASS was deployed on naval survey vessels like the USNS Bowditch, Dutton, and Michelson, utilizing 61 narrow beams at 12 kHz to achieve a swath width of about 1.15 times the water depth. In the mid-1960s, multibeam technology began transitioning to civilian oceanographic research through installations on U.S. Coast and Geodetic Survey ships, such as the Surveyor, Discoverer, and Researcher, which featured the Narrow Beam Echo Sounder (NBES) with 16 beams. These efforts involved collaborations between naval programs and academic institutions to adapt military prototypes for scientific seafloor studies. However, early systems grappled with limitations, relying on real-time film recording for data capture due to the absence of affordable digital storage, and delivered modest resolution constrained by beam spacing and acoustic challenges. Key contributors included Harold Farr, Paul Froelich, and Don White at Harris ASW for prototype leadership, alongside Howard Lustig and Arthur Rossoff for foundational concepts.

Key Milestones and Advancements

The first commercial multibeam echosounder, known as Sea Beam, was introduced in 1977 by Corporation and installed on the French research vessel Jean Charcot, featuring 16 beams each with a 2⅔° width and digital for real-time seafloor mapping across swaths up to 1.15 times the water depth, enabling efficient global ocean floor surveys. This system marked a pivotal shift from single-beam sonars by providing simultaneous depth measurements over a wide area, leveraging acoustic principles to resolve seafloor topography with unprecedented coverage. In the , advancements transitioned multibeam systems toward phased-array transducers, exemplified by Simrad's EM 100 introduced in , which utilized dynamic to generate over 60 beams and achieve swath widths extending up to five times the water depth in deep ocean environments. These developments, including systems like Hydrosweep and Furuno's equivalents, proliferated commercially across and survey vessels in multiple nations, enhancing resolution through narrower beam angles and improved for broader seafloor coverage. The 1990s saw widespread commercialization led by companies such as Simrad and Reson, with systems like the Simrad EM 12 operating at low frequencies around 12 kHz for deep-water up to 11,000 meters, while Reson's SeaBat series introduced higher-frequency models from 200 kHz to 400 kHz tailored for shallow-water surveys with resolutions suitable for coastal mapping. This frequency range expansion allowed versatile deployment across diverse marine environments, boosting adoption in hydrographic and scientific applications. During the 2000s, integration of multibeam echosounders with GPS and inertial navigation systems became standard, providing sub-decimeter positioning accuracy and attitude measurements as fine as 0.01° for roll and 0.02° for heading, which enabled bathymetric resolutions down to 1-5 meters in shallow waters through tightly coupled . These enhancements, seen in systems like and Reson models, significantly reduced positional errors in data , facilitating high-density seafloor models over large areas. In the 2020s, developments have incorporated AI-assisted for automated data cleaning and feature detection, as in Teledyne RESON's SeaBat T51-R, which includes AI controls for optimizing and target identification, alongside ultra-high-resolution capabilities with beam widths under 1° at frequencies up to 800 kHz for detailed imaging in complex terrains. Such innovations have further expanded swath efficiencies and speeds, supporting real-time applications in autonomous surveys.

Principles of Operation

Acoustic Fundamentals

Multibeam echosounders rely on the propagation of through to detect and the seafloor. in this context are compressional oscillations that travel as longitudinal waves, propagating at the local , which is approximately 1500 m/s in typical conditions. This speed varies primarily with (increasing by about 4.5 m/s per °C), (increasing by about 1.3 m/s per parts per thousand), and depth-related (increasing by about 1.6 m/s per 10 atmospheres). The λ\lambda of these waves is determined by the λ=c/f\lambda = c / f, where cc is the sound speed and ff is the , influencing the resolution and beam characteristics of the system. To measure depth, the system transmits short acoustic pulses, typically lasting 2 to 20 milliseconds, from a array. These pulses expand spherically into the water column, and the time-of-flight (TOF) is measured as the interval between transmission and reception of the returning . The depth dd is then calculated using d=(c×TOF)/2d = (c \times \text{TOF}) / 2, accounting for the round-trip path, with cc derived from a sound velocity profile (SVP) to correct for variations. The pulse duration affects vertical resolution, as echoes from closely spaced features may overlap if separated by less than half the pulse length. Upon reaching the , the acoustic pulse interacts through reflection and backscattering, governed by the mismatch in between and the bottom material. Acoustic impedance Z=ρcZ = \rho c, where ρ\rho is and cc is sound speed, for is approximately 1.5×1061.5 \times 10^6 Rayls (Rayls = kg/m²·s); significant mismatches (e.g., with rocky or sandy sediments) produce strong reflections. For flat , occurs, directing energy back along the incident path at near-normal incidence angles, while rough surfaces cause diffuse , spreading energy over a wider angular range and reducing specular returns. Backscattering specifically refers to the portion of scattered energy returning toward the receiver, which varies with composition—stronger from hard, impedance-contrasting materials like rock and weaker from soft sediments like . Frequency selection in multibeam echosounders balances , resolution, and . Low frequencies (10–50 kHz) are used for deep-water applications, offering greater penetration due to lower absorption but coarser resolution (longer wavelengths). High frequencies (200–500 kHz) are preferred for shallow-water, high-resolution mapping, providing finer detail (shorter wavelengths) but limited range. Several factors contribute to signal attenuation during propagation. Absorption converts acoustic energy to heat, increasing with frequency (e.g., roughly 50% loss at 12 kHz over 3000 m) and influenced by and . Spreading loss follows spherical , reducing intensity by 20 log10(r)_{10}(r) for range rr in meters. bends wave paths due to the SVP, where gradients in sound speed (e.g., from thermoclines) cause rays to curve toward slower-speed regions, potentially distorting depth estimates if unaccounted for.

Beamforming and Swath Geometry

Multibeam echosounders utilize techniques to create multiple simultaneous receive beams from echoes received by a linear , primarily employing phased-array methods that apply precise time delays or phase shifts to signals from individual elements. This electronic enables the formation of a contiguous fan of beams oriented to the vessel's track, allowing for wide-area seafloor mapping without mechanical movement of the transducers. The process relies on constructive and destructive interference to focus energy into narrow beams, with computational methods like the (FFT) often used to efficiently compute beam outputs from raw data. The swath geometry of these systems defines the across-track coverage, typically achieving a width of 4 to 7 times the depth, depending on , depth, and environmental conditions. Inner beams are directed near for high-resolution vertical measurements, while outer beams operate at grazing angles up to 60-70 degrees, extending the swath edges but potentially introducing greater uncertainty due to oblique incidence. This fan-shaped pattern ensures overlapping coverage along the survey track when the vessel moves forward, with total sector angles ranging from 120 to 140 degrees in modern configurations. Beam patterns in multibeam echosounders feature a variable number of beams, from 32 in early systems to over 1000 in high-resolution models, each with a narrow angular width of 0.5 to 2 degrees to achieve fine along-track and across-track resolutions. Early designs used equiangular spacing, where beams are separated by fixed angular intervals (e.g., 1 degree), resulting in denser soundings near the and sparser coverage at the swath edges. Contemporary systems often incorporate equi-distance spacing, dynamically adjusting beam angles to maintain uniform lateral intervals on the seafloor, thereby optimizing resolution and data density across the entire swath. The ping rate, or , determines the and along-track sampling density, reaching up to 30 Hz in mid-depth waters and higher (up to 60 Hz) in shallow environments to accommodate rapid vessel speeds. Each beam's on the seafloor—the ensonified area—is roughly the product of the beam's angular width and the to the bottom, scaling with depth and influencing the effective resolution of bathymetric . Variations in sound speed can refract beams and alter geometry, but these effects are typically compensated during .

System Components

Transducer Arrays

Multibeam echosounders employ arrays constructed primarily from piezoelectric ceramic materials, which convert into for transmission and vice versa for reception. These arrays are typically mounted on the ship's hull and consist of separate transmit and receive components to optimize . The transmit , often a high-power linear or flat configuration, generates a fan-shaped acoustic , while the receive , comprising multiple sensitive elements arranged in a linear fashion, captures returning echoes across a wide swath. Array configurations vary based on operational depth and vessel type, with the Mills Cross design being a standard for many systems, featuring orthogonal transmit and receive linear arrays to achieve precise . In this setup, the transmit array is aligned along the ship's track for along-track steering, while the receive array spans athwartship to form multiple beams perpendicular to the vessel's path. For deep-water applications, these configurations provide enhanced resolution, as seen in systems like the EM 300, where modular linear arrays (up to 8 modules each for transmit and receive) allow adjustable beam widths of 1° to 4°. Shallow-draft vessels often use flexible pod-mounted arrays to maintain stability and accessibility in confined waters. Operating frequencies and power levels are tailored to and resolution needs, with many modern systems supporting dual- or multi-frequency modes for versatility. For instance, the EM 300 operates at a nominal 30 kHz for deeper surveys, while the EM 2040 series spans 200–400 kHz in 10 kHz steps, enabling selection between high-resolution shallow-water mapping (e.g., 300–400 kHz) and moderate-depth coverage (e.g., 200 kHz). Transmit power can reach several kilowatts to ensure signal penetration, though exact levels depend on system design and are managed to avoid excessive energy use. Mounting considerations are critical to minimize acoustic interference, particularly from hull-generated bubbles that can attenuate signals. Transducers are often installed via over-the-side poles at the bow or in moon pools for temporary deployments, positioning them below the and away from propellers, thrusters, or turbulent flow areas to reduce and noise. Permanent hull mounts require smooth surfaces and sacrificial anodes to prevent , ensuring a clear acoustic . The evolution of transducer arrays has progressed from early analog mechanical systems to sophisticated digital phased arrays. Initial designs, such as the 1960s Sonar Array Sounding System (SASS), relied on fixed orthogonal arrays with limited , while the 1990s SeaBeam 2100 introduced digital processing for up to 151 dynamically steered beams using piezoelectric line arrays. Contemporary units, like the EM series, feature fully digital phased arrays with electronic steering, enabling real-time beam adjustment and multi-frequency operation without mechanical components. As of 2025, further advancements include configurable curved-array transducers, such as those in the WBMS X multibeam echosounder introduced in June 2025.

Signal Processing and Integration

In multibeam echosounders, signal acquisition begins with arrays capturing continuous analog echoes representing and phase information from the seafloor. These analog signals are then converted to discrete digital samples via analog-to-digital converters, typically at sampling rates of 1-3 milliseconds, enabling further computational . Bottom detection algorithms process these digitized echoes to identify the seafloor return, often employing thresholding to distinguish signal from by setting a minimum threshold, such as -40 dB, particularly in outer beams where returns are weaker. Complementary phase analysis merges data with phase information to enhance detection accuracy, stabilizing the bottom line in near-normal and oblique beams and reducing the need for manual corrections. Real-time processing involves digital beamforming, where (FFT) algorithms analyze time slices of the digitized data to form multiple steered beams, rejecting noise through dynamic thresholding that adapts per slice to suppress low-amplitude artifacts and side lobes. Gain control is achieved via time-varying amplification, which compensates for signal with range, ensuring consistent echo strengths across beams while applying to minimize sidelobe interference. Navigation integration synchronizes the echosounder with (GPS) receivers, inertial navigation systems (INS), and motion reference units (MRUs) to provide precise vessel positioning and orientation data. MRUs deliver high-frequency roll, pitch, and yaw measurements—typically with 0.03° RMS accuracy and 100 Hz update rates—for real-time compensation of platform motion, aligning acoustic beams with the and minimizing geometric distortions in the swath. Processed data are output in standardized raw formats such as extended Triton format (XTF) files, which encapsulate beam depths, amplitudes, and associated metadata including geodetic position from GPS, heading from gyrocompasses or INS, and sound velocity profiles to correct for ray bending. These formats facilitate seamless transfer to analysis software, preserving timestamped ancillary data for post-acquisition validation. Integration with platforms like Teledyne CARIS Onboard enables near-real-time preview of processed during surveys, applying automated corrections for motion and sound speed directly from the echosounder feed. Similarly, QPS Qimera supports onboard visualization of multibeam data, incorporating navigation metadata for immediate quality assessment and workflow efficiency.

Applications

Hydrographic and Bathymetric Mapping

Multibeam echosounders are essential for high-density bathymetric surveys that support , routing, and coastal zone management by providing comprehensive coverage with depths measured across a wide swath. These systems enable the creation of detailed models used in nautical charting and projects, ensuring safe and planning. In operations, for instance, multibeam data identifies sediment accumulation and verifies post-dredge depths to maintain required channel clearances. Similarly, for cable routing, the technology maps to avoid hazards like rocky outcrops or unstable sediments, while coastal zone management benefits from its ability to delineate nearshore features for and habitat preservation. To meet (IHO) standards, such as Order 1a for high-accuracy surveys in areas up to 100 meters depth, multibeam echosounders achieve total vertical uncertainty (TVU) of approximately 0.5 meters at shallow depths, calculated as TVU = √(0.5² + (0.013 × d)²), where d is depth in meters. This precision supports safety-of-navigation requirements under IHO S-44, which mandates 100% seafloor coverage and detection of features as small as 2 meters in depths ≤40 meters. Surveys conducted with these systems must also ensure total horizontal uncertainty (THU) of ≤5 meters + 5% of depth at 95% confidence, verified through and ground truthing. Coverage efficiency is a key advantage, with swath widths allowing full bottom ensonification at vessel speeds of 5-10 knots, significantly reducing survey time compared to single-beam echosounders that require dense trackline spacing. For example, in shallow waters (0-20 ), line spacing can be set to achieve 1-meter grid resolution for complete coverage, enabling surveys over large areas without gaps. This efficiency has been demonstrated in NOAA's Integrated Ocean and Coastal Mapping (IOCM) program, where multibeam systems on hydrographic vessels map U.S. coastal waters to support nautical charts and , covering thousands of square kilometers annually. In post-hurricane seabed change detection, multibeam echosounders facilitate rapid assessments of , deposition, and channel alterations, as seen in response to where identified navigation hazards and volume changes in affected coastal areas. For shallow water applications, higher-frequency systems operating at 400 kHz provide vertical accuracies approaching 0.1 meters, balancing resolution with swath width to map fine-scale features like sand waves or wrecks while adhering to IHO S-44 compliance for regulatory surveys. Data processing for , including sound speed corrections, ensures these models meet the required standards.

Environmental and Scientific Uses

Multibeam echosounders play a crucial role in mapping by leveraging data to classify types, coral reefs, and beds, supporting studies. Dual-frequency systems, operating at frequencies like 150 kHz and 400 kHz, enable high-accuracy discrimination of benthic habitats through spectral features such as and spectral skewness derived from bathymetric and analyses. For instance, classifiers applied to these data have achieved up to 86% accuracy in mapping complex geomorphologies, including on boulders and varied substrates like fine and gravel. Integrating water-column data further refines these maps; in studies at sites like , , processing acoustic energy 0–1 m above the with modeling improved macroalgae habitat detection, such as and brown communities, by enhancing producer accuracy by nearly 3%. In fisheries and marine mammal monitoring, multibeam echosounders configured upward-facing capture water-column imaging to detect fish schools and track migrations, providing non-invasive insights into . High-frequency systems, such as those at 0.9 MHz with wide fields of view, have documented temporal patterns, revealing large fish aggregations at night and smaller schools during daylight, alongside seals and cetaceans like orcas at sites in . Water-column data from these systems also facilitate 3D visualization of schooling behaviors in swimbladder-bearing fish species, aiding evaluations of without disturbance. For marine mammals, the technology supports behavioral studies, including predator-prey interactions during whale migrations, by resolving targets based on intensity and movement. Geological surveys benefit from multibeam echosounders in detecting volcanic and tectonic features, such as those along mid-ocean ridges, through high-resolution bathymetric mapping. The Schmidt Ocean Institute's R/V Falkor employs systems like the EM302 at 30 kHz to image deep-sea structures up to 8,000 meters, revealing and ridge morphologies during expeditions targeting tectonic boundaries. These surveys produce detailed 3D models of features like volcanic seamounts and fracture zones, contributing to understandings of and crustal formation. Archaeological applications utilize multibeam echosounders for high-resolution scans of shipwrecks and submerged sites, preserving in deep waters. In the Black Sea Project (2015–2017), dual-head EM2040 systems on remotely operated vehicles generated 10 cm resolution , enabling the discovery and 3D documentation of 65 wrecks from the to the AD, many exceptionally preserved in anoxic conditions below 150 m. This approach complements , facilitating accurate site mapping and management without physical disturbance. For climate research, multibeam echosounders monitor ice scour and sediment transport, informing models of sea-level rise and glacial dynamics. Bathymetric data from surveys on the Chukchi Borderland, Arctic Ocean, have identified parallel scours up to 1,000 m wide and 40 m deep, attributed to Pleistocene ice shelf grounding, which bulldozed sediments from adjacent plateaus and redistributed them westward. Such features provide evidence of past ice extents, aiding reconstructions of Arctic paleoclimate and predictions of future sediment mobilization under warming conditions.

Data Acquisition and Processing

Survey Procedures and Calibration

Pre-survey planning for multibeam echosounder surveys begins with patch testing to ensure system stability, typically conducted during readiness reviews or after any equipment modifications. Patch tests quantify biases in roll, pitch, heading, and timing by surveying a well-defined slope with 10-20% grade in sufficient water depth, allowing assessment of system performance across the sonar range using side scan passes on a standard target. Sound velocity profiling is also essential, performed every four hours using Conductivity-Temperature-Depth (CTD) instruments like Sea-Bird or to measure sound speed variations, with profiles applied during processing to correct for errors; daily or more frequent casts are required in variable environments to prevent discrepancies exceeding 1 m/s. Calibration techniques primarily involve detailed patch tests to address roll and pitch biases, latency, and beam pointing errors. For roll bias, surveys are conducted over flat areas in opposite directions at constant speed; pitch bias uses reciprocal lines over slopes; heading (yaw) tests with 25% overlap; and latency checks co-linear lines at varying speeds over sharp targets. Beam pointing calibration employs flat areas to align swaths and minimize outer beam wobble via adjustments between the multibeam system and motion reference unit. Corrections derived from these tests, such as angular and timing delays, are applied to position files or hardware installation parameters to ensure accuracy, with 95% confidence radii limited to 5 m for hull-mounted systems. During , protocols emphasize line spacing to achieve at least 100% overlap in each direction for full coverage, with swath widths adjusted based on water depth and system capabilities to ensure ensonification of the . Artifact avoidance includes selecting calm conditions and similar bottom profiles to the survey area, while monitoring and filtering multipath echoes or double returns using thresholds for depth, angle, or total propagated uncertainty (TPU). involves real-time checks for coverage gaps, noise levels from bubbles or vibrations, and beam consistency, often using software like CARIS HIPS to review swath data daily and identify systematic errors via crosslines. Standards from organizations like NOAA and ICES align with (IHO) S-44 Edition 6.1.0 (2022) guidelines for survey repeatability, requiring total propagated uncertainty (TPU) components—total vertical uncertainty (TVU) and total horizontal uncertainty (THU)—to meet specifications such as Order 1a/b. TVU = √(a² + (b × d)²) m, where d is depth in meters; for Order 1a/b, a = 0.5 m, b = 0.013; for Special Order, a = 0.25 m, b = 0.0075; and for the more stringent Exclusive Order introduced in 2022, a = 0.15 m, b = 0.0075. These align with NOAA Specifications and Deliverables (HSSD) 2025 for high-accuracy hydrographic mapping, ensuring error budgets remain within allowable limits, with crossline comparisons assessing standard deviations against IHO thresholds for vertical and positional accuracy.

Backscatter Analysis and Visualization

Bathymetric processing of multibeam echosounder begins with cleaning to remove outliers, such as those caused by refraction or , ensuring before gridding. The Combined Uncertainty and Bathymetry Estimator () is widely used for gridding, as it directly generates digital terrain models (DTMs) by estimating depth and at grid nodes while accounting for sounding errors from various sources like positioning and sound velocity profiles. employs multiple testing to evaluate alternative depth surfaces, selecting the most consistent one based on statistical models, which results in variable-resolution DTMs that adapt to and terrain complexity. Backscatter normalization corrects raw intensity data for factors including grazing incidence angle, water depth, and acoustic absorption to enable comparable measurements across surveys. This process typically involves time-varied gain adjustments and angular response modeling, producing normalized backscatter mosaics that highlight seabed reflectivity variations for habitat mapping. Angular response curves, derived from normalized backscatter as a function of incidence angle, facilitate sediment classification by revealing characteristic patterns, such as higher backscatter at nadir for coarse sediments and decreasing trends for finer ones. Visualization of processed data utilizes specialized software to create interpretable outputs. FMGT (Fledermaus Geocoder Toolbox) processes into georeferenced mosaics, supporting 3D renders and hillshade overlays for . Tools like integrate these with for contour generation and volume computations, aiding in seafloor feature identification. Advanced techniques include imaging for detecting mid-water targets like gas plumes or schools, where anomalies are thresholded and tracked volumetrically. approaches, such as models, automate feature extraction from mosaics and angular responses, improving seabed habitat classification accuracy when fused with limited ground-truth samples. Final products encompass mosaic images for visual characterization, volumetric estimates from DTMs for resource assessment, and exports in GIS-compatible formats like to support in .

Advantages and Limitations

Performance Benefits

Multibeam echosounders provide significant coverage advantages over traditional single-beam systems by emitting multiple acoustic beams in a fan-shaped swath, enabling full seafloor ensonification across a wide area rather than a single narrow track. This full swath mapping capability allows for comprehensive bathymetric in a single pass, drastically reducing survey time for large areas by up to 90%, as the system can acquire data 10 times faster than single-beam echosounders. In terms of resolution, multibeam systems deliver high across-track detail, capable of detecting seafloor features smaller than 1 meter, such as submerged obstacles or small-scale variations, without relying on methods common in single-beam surveys. This enhanced resolution stems from the dense array of beams, which can achieve down to sub-meter levels in shallow waters, improving the accuracy of topographic mapping. The data richness of multibeam echosounders arises from their ability to simultaneously capture depth soundings and intensity across the swath, yielding multi-parameter datasets that support integrated analyses for habitat classification, sediment characterization, and geological interpretation. This dual-output functionality enables more versatile applications compared to single-beam systems, which primarily provide depth-only profiles. Multibeam echosounders enhance cost-effectiveness by lowering operational expenses per square kilometer mapped, particularly in extensive surveys like those for offshore site assessments, where the broad coverage minimizes vessel time and fuel consumption. For instance, in bathymetric surveys supporting development, the efficiency gains from swath mapping reduce overall project costs by optimizing data acquisition logistics. Reliability in multibeam systems is bolstered by advanced techniques, which use inertial sensors to correct for vessel heave, pitch, and roll, minimizing depth errors in dynamic conditions. Additionally, multi-ping averaging processes multiple acoustic returns to improve signal-to-noise ratios, ensuring consistent and accurate soundings even in challenging environments.

Technical Challenges and Future Developments

Multibeam echosounders face significant limitations in very shallow water depths below 5 meters, where proximity to the seafloor restricts swath width due to system geometry, leading to inefficient coverage and potential gaps that require additional survey lines for complete mapping. High costs associated with deep-water systems, often exceeding hundreds of thousands of dollars per unit for survey-grade equipment including heads, motion reference units, and processing software, pose barriers for smaller organizations and emerging markets. These systems are also highly sensitive to , such as wind-generated bubbles that attenuate acoustic signals and distort outer swath data, or thermoclines that alter sound speed profiles and degrade depth accuracy without frequent profiling. Additionally, rough sea states exacerbate bubble entrainment and , further reducing effective range and data quality in hull-mounted configurations. The massive data volumes generated by multibeam surveys, often reaching terabytes per project from high-resolution and imaging, demand substantial storage and computational resources, complicating post-processing and transmission. For instance, even a single survey can produce around 2 GB of data, scaling to terabytes with extended operations and requiring advanced software like Echoview for handling. Emerging trends address these challenges through integration with autonomous underwater vehicles (AUVs) and unmanned surface vehicles (USVs), enabling gapless coverage in hard-to-reach areas; for example, the iWBMS multibeam system on the mKurs USV achieved 10 cm resolution full coverage in a 79.7 m deep lake with minimal human intervention. Synthetic aperture sonar techniques combined with multibeam arrays enhance finer resolution by forming virtual apertures that overcome along-track limitations, producing detailed 3D images capable of separating adjacent targets in experimental tank tests. Advancements in AI and automation, including , facilitate real-time artifact removal and ; semi-supervised models using k-nearest neighbors achieve 96% accuracy in filtering noise from multibeam data, while ensemble classifiers reach 98% for distinguishing schools and gas seeps. Recent developments, such as the EM 2040 C, incorporate automated filtering like slant-range signal normalization to remove sidelobe artifacts, improving detection in multispectral data at 200–400 kHz. Future directions include higher frequencies up to 1 MHz for micro-bathymetry, enabling sub-centimeter resolution in compact systems for close-range, highly detailed mapping. Multi-frequency systems, operating simultaneously at low bands like 100 kHz and 200 kHz, optimize penetration and resolution trade-offs by reducing noise and identifying types for . As of 2025, new systems like the Teledyne SeaBat T51-S for ROV/AUV deployment and updated EM 2040 MKII with enhancements continue to advance integration with autonomous platforms.

References

  1. https://oceanexplorer.noaa.gov/technology/sonar-multibeam/
  2. https://lismap.uconn.edu/wp-content/uploads/sites/2333/2018/11/SeaBeamMultibeamTheoryOperation.pdf
  3. https://data.ngdc.noaa.gov/instruments/remote-sensing/active/profilers-sounders/acoustic-sounders/kongsberg_em710_data_sheet.pdf
  4. https://www.kongsberg.com/globalassets/kongsberg-discovery/commerce/seafloor-mapping/hws/em-124-multibeam-echo-sounder/
  5. https://scholars.unh.edu/cgi/viewcontent.cgi?article=1103&context=ccom
  6. https://pubs.usgs.gov/of/2002/0005/
  7. https://www.hydro-international.com/content/article/a-note-on-fifty-years-of-multi-beam
  8. https://apps.dtic.mil/sti/tr/pdf/ADA333800.pdf
  9. https://www.researchgate.net/publication/326323913_The_Invention_and_Developing_of_Multibeam_Echosounder_Technology
  10. https://oceanexplorer.noaa.gov/history/timeline-the-age-or-electronics-2-1946-1970/
  11. https://www.scribd.com/document/388334416/The-Development-of-the-Multibeam-Echosounder
  12. https://www.hydro-international.com/articles/a-note-on-fifty-years-of-multi-beam
  13. https://dosits.org/galleries/technology-gallery/observing-the-sea-floor/multibeam-echosounder/
  14. https://docs.iho.int/mtg_docs/rhc/MACHC/MACHC13/Presentations/03-Kongsberg.pdf
  15. https://www.researchgate.net/publication/346894402_Chapter_2_Multi-beam_Bathymetric_Technology
  16. https://www.gebco.net/sites/default/files/documents/cen_conf_mayer.pdf
  17. https://www.macartney.de/fileadmin/redakteur/Hydrographie/Multibeam/SeaBat_T51/Teledyne_Reson_SeaBat_T51-R_Product_leaflet_PLD22268-3.pdf
  18. https://dosits.org/decision-makers/tutorials/science/sound-speed/
  19. https://iho.int/uploads/user/pubs/cb/c-13/english/C_13_Chapter_3_December2010.pdf
  20. https://www.sciencedirect.com/science/article/pii/S0003682X15002054
  21. https://acousticstoday.org/wp-content/uploads/2017/07/Article_3of4_from_ATCODK_3_1.pdf
  22. https://livrepository.liverpool.ac.uk/3176900/1/070003_1_2.0001801.pdf
  23. https://scholars.unh.edu/cgi/viewcontent.cgi?article=1453&context=thesis
  24. https://data.ngdc.noaa.gov/instruments/remote-sensing/active/profilers-sounders/acoustic-sounders/kongsberg_em300_product_description.pdf
  25. https://archimer.ifremer.fr/doc/00000/1141/793.pdf
  26. https://www.hydro-international.com/content/article/state-of-the-art-in-multibeam-echosounders
  27. https://www.kongsberg.com/globalassets/kongsberg-discovery/commerce/seafloor-mapping/em2040-mkii/em-sector-coverage-beam-spacing-modes.pdf
  28. https://www.ctscorp.com/Resources/Blog/Piezoelectric-Receivers-in-Multibeam-Echosounders
  29. https://www.kongsberg.com/contentassets/bde3261d49644a8f8b40c5b0f08b8df9/417418ac_em2040p_installation_manual_en.pdf
  30. https://www.kongsberg.com/globalassets/kongsberg-discovery/commerce/seafloor-mapping/em2040-mkii/472405ab_em2040mk2_installation_manual_en.pdf
  31. https://cdn1.shipserv.com/ShipServ/pages/profiles/54162/documents/EM-2040-Product-Description.pdf
  32. https://www.marketsandmarkets.com/Market-Reports/multibeam-echo-sounder-mbes-systems-market-228346611.html
  33. https://academic.oup.com/icesjms/article/66/6/1015/694054
  34. https://www.researchgate.net/figure/Bottom-detection-from-ER60-echosounder-data-a-Bottom-line-computed-by-the-standard_fig5_44841859
  35. https://www.academia.edu/19358518/detection_with_the_ME70_multibeam_echosounder_2
  36. https://mac.unols.org/wp-content/uploads/2021/06/20130124_Revelle_QAT_report-final.pdf
  37. https://imagenex.com/assets/images/downloads/430-041-00_Set_up_and_Configuration_of_the_Imagenex_DT101Xi__DT102Xi.pdf
  38. https://geo-matching.com/products/ms8240-mbes-multibeam-echosounder
  39. https://www.teledynecaris.com/en/products/caris-onboard/
  40. https://publicdownload.qps.nl/Qimera/Qimera-2.5.4-Documentation.pdf
  41. https://nauticalcharts.noaa.gov/publications/docs/standards-and-requirements/specs/hssd-2019.pdf
  42. https://iho.int/uploads/user/pubs/standards/s-44/S-44_Edition_6.1.0.pdf
  43. https://nauticalcharts.noaa.gov/about/docs/about/ocean-mapping-capabilities.pdf
  44. http://sandy.ccom.unh.edu/publications/library/Effective_Object_Detection_with_Bathymetric_Sonar_Systems_for_Post_Storm_Response_Final.pdf
  45. https://data.ngdc.noaa.gov/platforms/ocean/nos/DAPRs/OPR-W387-TJ-22_DAPR.pdf
  46. https://www.sciencedirect.com/science/article/pii/S0025322720301274
  47. https://aslopubs.onlinelibrary.wiley.com/doi/10.1002/lno.12160
  48. https://pmc.ncbi.nlm.nih.gov/articles/PMC9750035/
  49. https://www.sciencedirect.com/science/article/abs/pii/S0272771414000900
  50. https://schmidtocean.org/technology/seafloor-mapping/
  51. https://www.sciencedirect.com/science/article/abs/pii/S0967063719302328
  52. https://www.cambridge.org/core/journals/quaternary-research/article/multibeam-bathymetric-and-sediment-profiler-evidence-for-ice-grounding-on-the-chukchi-borderland-arctic-ocean/0094EA2DED4AC228F0753CB96A9588D3
  53. https://nauticalcharts.noaa.gov/publications/docs/standards-and-requirements/fpm/field_procedures_manual_2020.pdf
  54. https://www.nauticalcharts.noaa.gov/publications/documents/HSSD_2025-0-00.pdf
  55. https://scholars.unh.edu/cgi/viewcontent.cgi?article=2217&context=ccom
  56. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2002GC000486
  57. https://sanctuaries.noaa.gov/science/conservation/intelmann2.html
  58. https://www.sciencedirect.com/science/article/abs/pii/S0278434313001246
  59. https://www.mdpi.com/2076-3263/9/3/126
  60. https://pmc.ncbi.nlm.nih.gov/articles/PMC5751054/
  61. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2017jc013638
  62. https://www.hydro-international.com/content/news/new-version-of-wassp-s3-multibeam-echosounder-unveiled
  63. https://www.mdpi.com/2504-446X/6/10/294
  64. https://www.totalhydrographic.com.au/multibeam-or-single-beam-survey/
  65. https://apps.dtic.mil/sti/tr/pdf/ADA355042.pdf
  66. https://www.unmannedsystemstechnology.com/2018/07/using-autonomous-surface-vehicles-for-offshore-wind-farm-support/
  67. https://iocm.noaa.gov/standards/Standard_Ocean_Mapping_Protocol_draft_Feb2023.pdf
  68. https://www.mdpi.com/1424-8220/21/9/2999
  69. https://norbit.com/media/Seabed-Gazette-2024_LR.pdf
  70. https://pubs.aip.org/asa/jasa/article/145/5/3177/671389/Theoretical-and-experimental-study-on-multibeam
  71. https://www.mdpi.com/2072-4292/12/9/1371
  72. https://r2sonic.com/products/technical-modes/multifrequency-bathymetry/
  73. https://www.teledynemarine.com/teledyne-marine-launches-seabat-t51-s-multibeam
  74. https://oceannews.com/news/subsea-and-survey/kongsberg-release-new-features-on-the-em-2040-mkii-multibeam-echosound/
Add your contribution
Related Hubs
User Avatar
No comments yet.