Side Scanning Sonars are a type of Sonar system that is extensively used for developing images of large areas of the seabed. Sonar is an acronym for Sound Navigation and Ranging - it involves using the propagation of sound under the sea surface mostly for the purpose of locating or communicating with other ships. Side Sonars are a widely used tool for mapping of the sea floor for various purposes such as identification of underwater objects and formation of nautical charts.
A German scientist by the name of Dr. Julius Hagemann is credited to be one of the inventors of the side scan sonar. He was not the only person to experiment with this system though. The Scripps Institution of Oceanography and the Hudson Laboratories were two American scientific laboratories that did pioneering work on the experimental side scan sonar technology during the 1950s. The MIT, another hallowed American scientific institution, also delved into side scan sonar research, which was spearheaded by Dr. Harold Edgerton. Details can be found here. The first commercial side scan sonar systems came out as early as the 1960s though mass production of sophisticated and affordable systems happened only in the 80s.
So how does this technology work? The crux of this tool is a sonar device that is designed to emit pulses in a fan shape downwards towards the floor of the ocean at a wide angle; the pulses are emitted in a perpendicular fashion in respect to the path of the sensor which is usually located either on a ship on the surface of the water or on a submarine. This fan shaped beam sends out acoustic reflections as it hits the ocean floor, the intensity of which is recorded as cross-track slices in a series. When this entire series of slices are put together as a whole, they present an image of the bottom of the sea within the coverage area of the emitted beam.
The higher the frequency of sound used in side scan sonar imaging, the better will be the resolution and the lesser will be the range covered. Usually, this sound instrument employs a sound frequency range of 100 to 500 kHz. It finds good use in the field of maritime archaeology where extensive surveys of the sea bed are carried out using this technique. Images provided by side scan sonars along with samples taken from the sea bed are used to identify and understand the various types of materials that make up the sea floor. In the shipping industry, this form of sound technology is essential to identify any kind of obstruction on the seabed that might be harmful to shipping. Similarly, the oil and gas sector uses side scan sonar technology to detect debris on the sea floor that might stand in the way of installations on the seabed. Also, defects in the oil pipelines that have been laid on the sea floor can also be checked by using this technology. Side scan sonar technology is also widely used in fishery and environmental research and even in military operations to detect mines on the sea floor. Raytheon, Edo Corp and Northrop Grumman are some of the leading producers of high frequency side scanning sonar systems.
The side scanning sonar technology is also used to search for drowned people by the Law control, search and rescue personnel.
Details of how this technique is used by these personnel to search for drowned people can be found at http://www.mindsprings.com.
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