Editing Side-scan sonar

{{Short description|Tool for seafloor mapping}}
{{Refimprove|date=June 2008}}
[[File:Side-scan sonar.svg|thumb|right|{{center|Diagram of sidescan sonar}}]]

'''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 [[Seafloor mapping|create an image]] of large areas of the sea floor.

==Uses==
Side scan sonar is used to image large areas of the seafloor quickly. Applications include [[archaeological survey|surveys]] for [[marine archaeology]], shipwreck hunting, [[Search and rescue|search and recovery (SAR)]], and [[environmental monitoring]]. <ref>{{Cite web |title=A Smooth Operator's Guide to Underwater Sonars and Acoustic Devices |url=https://bluerobotics.com/learn/a-smooth-operators-guide-to-underwater-sonars-and-acoustic-devices/ |access-date=2024-01-12 |website=Blue Robotics |language=en-US}}</ref> 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 [[echo sounding|bathymetric soundings]] and [[sonar#Sub-bottom profiling|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]] (called a “towfish”), or mounted on the ship's [[hull (watercraft)|hull]].  The intensity of the [[acoustics|acoustic]] reflections from the seafloor of this fan-shaped [[light beam|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. <ref>{{Cite web |title=A Smooth Operator's Guide to Underwater Sonars and Acoustic Devices |url=https://bluerobotics.com/learn/a-smooth-operators-guide-to-underwater-sonars-and-acoustic-devices/ |access-date=2024-01-18 |website=Blue Robotics |language=en-US}}</ref> The sound [[frequency|frequencies]] used in side-scan sonar usually range from 100 to 500 [[kilohertz|kHz]]; higher frequencies yield better [[Temporal resolution|resolution]] but less range.

==History==
[[File:Laevavrakk "Aid".png|thumb| Side-scan sonar image of shipwreck "Aid" in [[Estonia]]]]
[[File:Lakemurray-wyse ferry Bridge sonar.jpg|thumb|right| Side-scan sonar image of submerged bridge at the bottom of [[Lake Murray (South Carolina)|Lake Murray]] in South Carolina]]

===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 "tow fish" and pulled by a tow cable.

Up until the mid-1980s, commercial side scan 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 drive]]s or [[Solid-state drive|solid-state media]] - the data is typically displayed in grayscale or color images, known as side scan sonograms, which provide a visual representation of the underwater environment. <ref>{{Cite web |title=A Smooth Operator's Guide to Underwater Sonars and Acoustic Devices |url=https://bluerobotics.com/learn/a-smooth-operators-guide-to-underwater-sonars-and-acoustic-devices/ |access-date=2024-01-12 |website=Blue Robotics |language=en-US}}</ref>

===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<ref>{{cite web|url=https://patents.google.com/patent/US4197591|title=Facsimile recording of sonic values of the ocean bottom|author=Julius Hagemann|date=1958|publisher=[[United States Patent Office]]}}</ref> 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===
[[File:Choctaw sonar image.jpg|thumb|right|side-scan image of the freighter [[SS Choctaw|''Choctaw'']]]]
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 12&nbsp;kHz side-scan sonar to find the sunken Vineyard Lightship in Buzzards Bay, Massachusetts. A team led by [[Martin Klein (engineer)|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 (archeologist)|George Bass]] find a 2000-year-old ship off the coast of Turkey. In 1968 Klein founded Klein Associates (now [[MIND Technology, Inc.|KLEIN - A MIND Technology Business]]) and continued to work on improvements including the first commercial high frequency (500&nbsp;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 (now Klein Marine Systems, Inc.) produced the first commercial side-scan sonar training videos and the first ''Side Scan Sonar Training Manual'' and two oceanographers found the [[Wreck of the RMS Titanic|wreck of the RMS ''Titanic'']].

For surveying large areas, the GLORIA sidescan sonar was developed by Marconi Underwater Systems and the [[National Oceanography Centre|Institute of Oceanographic Sciences]] (IOS) for [[Natural Environment Research Council|NERC]]. GLORIA stands for Geological Long Range Inclined [[Asdic]].<ref>[https://archive.today/20130202223648/http://www.springerlink.com/content/q3g86p278t08838p/ Rusby et al. 1973]</ref> It was used by the [[United States Geological Survey|US Geological Survey]] and the IOS in the UK to obtain images of continental shelves worldwide. It operated at relatively low frequencies to obtain long range.  Like most side-scan sonars, the GLORIA instrument is towed behind a ship. GLORIA has a ping rate of two per minute, and detects returns from a range of up to 22&nbsp;km either side of the sonar fish.

==See also==
* {{annotated link|Aperture synthesis}}
* {{annotated link|Beamforming}}
* {{annotated link|Phased array}}
* {{annotated link|Sonar 2087}}
* {{annotated link|Synthetic aperture sonar}}

==References==
{{reflist}}

==External links==
{{Commons category|Side-scan sonar}}
* [http://www.marinesonic.com Marine Sonic HDS Sonar System]
* [http://www.abc.se/~pa/mar/sidescan.htm Side Scan Sonar]
* [http://gralston1.home.mindspring.com/Sidescan.html Use of side scan sonar to recover drowning victims] {{Webarchive|url=https://web.archive.org/web/20080226025929/http://gralston1.home.mindspring.com/Sidescan.html |date=2008-02-26 }}
* Pictures and description of [https://web.archive.org/web/20040819073648/http://woodshole.er.usgs.gov/operations/sfmapping/towvehicles.htm USGS Benthos SIS-1000] sidescan sonar tow vehicle.
* [http://chartmaker.ncd.noaa.gov/HSD/wrecks.html NOAA's use of sidescan and multibeam sonar] {{Webarchive|url=https://web.archive.org/web/20010208105936/http://chartmaker.ncd.noaa.gov/HSD/wrecks.html |date=2001-02-08 }} to make official US nautical charts
* Examples of [http://www.oicinc.com/ds_digital_sidescan.html geocoded sidescan images]
* A [http://delph.ixblue.com/readings/ guide to Side-Scan Sonar acquisition and processing] {{Webarchive|url=https://web.archive.org/web/20130501103154/http://delph.ixblue.com/readings/ |date=2013-05-01 }} and [http://delph.ixblue.com/sonar/gallery/ image galleries] {{Webarchive|url=https://web.archive.org/web/20130501090004/http://delph.ixblue.com/sonar/gallery/ |date=2013-05-01 }}
* Tritech Knowledge Base – [http://www.tritech.co.uk/uploaded_files/Side%20Scan%20Sonars.pdf Side Scan Sonars]
* [http://coastalmap.marine.usgs.gov/gloria U.S. Geological Survey GLORIA Mapping Program] {{Webarchive|url=https://web.archive.org/web/20080704171445/http://coastalmap.marine.usgs.gov/gloria/ |date=2008-07-04 }}

{{hydroacoustics}}

{{DEFAULTSORT:Side-Scan Sonar}}
[[Category:Sonar]]