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Sidescan Sonar Systems Banner
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History

Harold Edgerton, a professor of electrical engineering at the Massachusetts Institute of Technology, developed sidescan sonar technology for use in the civilian community in the early 1960’s. Prior to developing sidescan, Edgerton was known for his work with photographic systems and “stopping time” via pictures. He applied a similar approach to mapping the seafloor using “flashes” of sound to create a narrow “image” of the underlying terrain and then stacking these images in a continuous, long “picture” as the sonar was towed along by a ship.  Many of the names that we now associate with underwater exploration and mapping are people who trained with Edgerton during the early days of sidescan development; Marty Klein and Ed Curley were students of Edgerton who would later go on to found Klein Associates Inc. and EPC where you can purchase sidescan sonars and other ocean instrumentation.  Another Edgerton student was Sam Raymond, founder of Benthos, which markets transponders and deep-ocean camera systems.

 
How Sidescan Sonars Work

Sidescan sonars are among the simplest seafloor mapping tools that you can use.
In their towed configuration they consist of a subsurface unit called a towfish, a cable for towing and transmitting information, and a topside system that is used to process data and transmit commands. Sidescan sonars that work on autonomous underwater vehicles (AUV’s) don’t require the cable; instead commands are pre-programmed into the AUV’s onboard computer guidance system.  In the AUV case, a topside computer is still useful for downloading data and evaluating the performance of the sonar while at sea.

The sidescan sonar towfish typically includes the sonar transducers, electronics and their pressure housings and flotation. Over the decades as the technology for creating flotation and electronics has improved and become more compact, sidescan towfish have evolved from cumbersome systems (Figure 1) into lightweight vehicles that can be launched from small platforms with limited handling capabilities (Figure 2).

Sidescan Sonar System in 1965
Figure 1 - Sidescan sonar being deployed from the NOAA ship Surveyor in 1965. Note the “Danger: High Voltage”
sign. See http://oceanexplorer.noaa.gov/history/electronic/1946_1970/media/sonar.html.

 
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