Side-scan sonar

Diagram of sidescan sonar

Submerged bridge in 48m (160 ft) of fresh water seen on sidescan sonar imagery at Lake Murray (South Carolina), using a Humminbird 981c Side Imaging system

Side-scan sonar image of shipwreck "Aid" in Estonia.

Side-scan sonar (also sometimes called side scan sonar, sidescan sonar, side imaging sonar, side-imaging sonar and bottom classification sonar) is a category of sonar system that is used to efficiently create an image of large areas of the sea floor.

Uses

Side-scan sonar may be used to conduct surveys for marine archaeology; in conjunction with seafloor samples it is able to provide an understanding of the differences in material and texture type of the seabed. Side-scan sonar imagery is also a commonly used tool to detect debris items and other obstructions on the seafloor that may be hazardous to shipping or to seafloor installations by the oil and gas industry. In addition, the status of pipelines and cables on the seafloor can be investigated using side-scan sonar. Side-scan data are frequently acquired along with bathymetric soundings and sub-bottom profiler data, thus providing a glimpse of the shallow structure of the seabed. Side-scan sonar is also used for fisheries research, dredging operations and environmental studies. It also has military applications including mine detection.

How it works

Side-scan uses a sonar device that emits conical or fan-shaped pulses down toward the seafloor across a wide angle perpendicular to the path of the sensor through the water, which may be towed from a surface vessel or submarine, or mounted on the ship's hull. The intensity of the acoustic reflections from the seafloor of this fan-shaped beam is recorded in a series of cross-track slices. When stitched together along the direction of motion, these slices form an image of the sea bottom within the swath (coverage width) of the beam. The sound frequencies used in side-scan sonar usually range from 100 to 500 kHz; higher frequencies yield better resolution but less range.

History

Technology

The earliest side-scan sonars used a single conical-beam transducer. Next, units were made with two transducers to cover both sides. The transducers were either contained in one hull-mounted package or with two packages on either side of the vessel. Next the transducers evolved to fan-shaped beams to produce a better "sonogram" or sonar image. In order to get closer to the bottom in deep water the side-scan transducers were placed in a "towfish" and pulled by a tow cable.

Up until the mid-1980s, commercial sidescan images were produced on paper records. The early paper records were produced with a sweeping plotter that burned the image into a scrolling paper record. Later plotters allowed for the simultaneous plotting of position and ship motion information onto the paper record. In the late 1980s, commercial systems using the newer, cheaper computer systems developed digital scan-converters that could mimic more cheaply the analog scan converters used by the military systems to produce TV and computer displayed images of the scan, and store them on video tape. Currently data is stored on computer hard drives or solid-state media.

Military application

One of the inventors of side-scan sonar was German scientist, Dr. Julius Hagemann, who was brought to the US after World War II and worked at the US Navy Mine Defense Laboratory, Panama City, FL from 1947 until his death in 1964. His work is documented in US Patent 4,197,591^[1] which was first disclosed in Aug 1958, but remained classified by the US Navy until it was finally issued in 1980. Experimental side-scan sonar systems were made during the 1950s in laboratories including Scripps Institution of Oceanography and Hudson Laboratories and by Dr. Harold Edgerton at MIT.

Military side-scan sonars were made in the 1950s by Westinghouse. Advanced systems were later developed and built for special military purposes, such as to find H-Bombs lost at sea or to find a lost Russian submarine, at the Westinghouse facility in Annapolis up through the 1990s. This group also produced the first and only working Angle Look Sonar that could trace objects while looking under the vehicle.

Commercial application

The first commercial side-scan system was the Kelvin Hughes "Transit Sonar", a converted echo-sounder with a single-channel, pole-mounted, fan-beam transducer introduced around 1960. In 1963 Dr. Harold Edgerton, Edward Curley, and John Yules used a conical-beam 12kHz side-scan sonar to find the sunken Vineyard Lightship in Buzzards Bay, Massachusetts. A team led by Martin Klein at Edgerton, Germeshausen & Grier (later E.G. & G., Inc.) developed the first successful towed, dual-channel commercial side-scan sonar system from 1963 to 1966. Martin Klein is generally considered to be the "father" of commercial side-scan sonar. In 1967, Edgerton used Klein's sonar to help Alexander McKee find Henry VIII's flagship Mary Rose. That same year Klein used the sonar to help archaeologist George Bass find a 2000-year-old ship off the coast of Turkey. In 1968 Klein founded Klein Associates, Inc.(now L-3/Klein) and continued to work on improvements including the first commercial high frequency (500 kHz) systems and the first dual-frequency side-scan sonars, and the first combined side-scan and sub-bottom profiling sonar. In 1985, Charles Mazel of Klein Associates produced the first commercial side-scan sonar training videos and the first Side Scan Sonar Training Manual.

For surveying large areas, the GLORIA sidescan sonar was developed by Marconi Underwater Systems and the Institute of Oceanographic Sciences (IOS) for NERC. This operated at relatively low frequencies to obtain long range. It was used by the US Geological Survey and the IOS in the UK to obtain images of continental shelves world-wide.

Manufacturers

Manufacturers of higher frequency side-scan sonar systems include Furuno, Sonardyne, Lowrance, Simrad, Raytheon, Northrop Grumman (formerly Westinghouse), EdgeTech (formerly EG&G), C-MAX Ltd., L-3/Klein Associates, J.W. Fishers Mfg. Inc., Imagenex Technology Corp., RESON A/S, Sonatech Inc., Benthos (the sonar formerly produced by Datasonics), WESMAR, Marine Sonic Technology, Kongsberg Maritime, Geoacoustics, EDO Corporation, Ultra Electronics, Humminbird (Techsonic Industries Inc), and Deep Vision Technologies.

Shallow-water side scan systems, Tritech and deeper rated side scan systems.

References

↑ Julius Hagemann (1958). "Facsimile recording of sonic values of the ocean bottom". United States Patent Office.

External links

Wikimedia Commons has media related to Side-scan sonar.

Marine Sonic HDS Sonar System
Side Scan Sonar
Use of side scan sonar to recover drowning victims
Pictures and description of USGS Benthos SIS-1000 sidescan sonar tow vehicle.
NOAA's use of sidescan and multibeam sonar to make official US nautical charts
Examples of geocoded sidescan images
A guide to Side-Scan Sonar acquisition and processing and image galleries
Tritech Knowledge Base - Side Scan Sonars

Hydroacoustics

Sonar	Active acoustics Baffles (submarine) Bistatic sonar Echo sounding Fessenden oscillator GLORIA sidescan sonar Multibeam echosounder Passive acoustics Scientific echosounder Side-scan sonar Sonar beamforming Sonobuoy Surveillance Towed Array Sensor System Synthetic aperture sonar Towed array sonar Upward looking sonar

Ocean acoustics	Acoustic network Acoustic release Acoustic Doppler current profiler Acoustic seabed classification Acoustical oceanography Hydrophone Long baseline acoustic positioning system Ocean acoustic tomography Short baseline acoustic positioning system Sofar bomb SOFAR channel Sound speed gradient Sound velocity probe Ultra-short baseline Underwater acoustics Underwater acoustic communication Underwater acoustic positioning system

Acoustic ecology	Acoustic survey in fishing Acoustic tag Animal echolocation Beached whale Deep scattering layer Fishfinder Fisheries acoustics Hearing range of marine mammals Marine mammals and sonar Whale song

Related topics	Acoustic signature Bioacoustics Biophony Geophysical MASINT Hydrographic survey Noise map Soundscape

This article is issued from Wikipedia - version of the Sunday, March 13, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.