Side-Scan

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Side scan sonar surveys

Are you an individual or company in need of a highly detailed marine survey? GPSCharts.com can offer you the services you require, be it wreck locations, bottom survey, inspections or drowned victim search, we can assist you at very competitive prices.

What is side scan sonar ?

Side scan sonar works like an underwater radar and is the best tool in existence for locating submerged items as small as a 5 gallon bucket. Regardless of visibility in the water the sound pulses penetrates hundreds of meters to each side of the sonar tow fish. An incredibly accurate and high-resolution picture of the seabed and any objects lying upon it is displayed on a computer screen. Massive areas can quickly and efficiently be surveyed.

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Side scan sonar

Side Scan Sonar is one of the most accurate systems for imaging large areas of the ocean floor. The sonar transducers (the device that sends and receive the acoustic pulses) are mounted in a torpedo like tow fish or are mounted on the vessel. Side Scan transmits an acoustic beam 86 degrees from the tow vessels path to each side as portrayed in the above illustration. This beam propagates into the water and across the seabed. The ocean floor and any objects lying upon it, reflect a portion of the sound energy back in the direction of the sonar . The sensitive sonar head receives these reflections, amplifying them and then send them to a sonar data processor and display. Images produced by quality sonar systems are highly accurate and can be used to delineate even very small objects as small as 1.5 inches.

Side Scan Sonar’s are used in a variety of applications such as locating pipeline or cable routes, shipwreck location; mine hunting, downed aircraft search and lost cargo search operations .As can be seen from the images below.

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A: Boat centerline B: First Bottom return = C: Water Depth ; D Sunken Piling ; E riprap G standing piling F steel break water H sand ripples . There was no question in the sonar printout on what is present on the seafloor.

With a Side Scan Sonar you can see hundreds of feet to each side of the tow fish with incredible detail. The acoustic signal is transmitted along two 86-degree swaths one on each side of the track line, from the horizontal plane to the bottom. Wrecks that were previously extremely difficult to look for due to uncertain positions are now possible to find.

The tow fish operates at 262khz, 455khz, 800khz, which enables a very high resolution. Surveys down to a depth of 150 meters are possible. The tow fish has a swath of 300ft that (150tf to each side of the tow fish)

 

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Examining the shadow from the wreck, you get an idea of how the silhouette of the wreck looks like. This appears to be an old AMF bow rider. As can be seen on the shadow the windshield is still in place and outboard are also still standing upright. The wreck stands about 3 feet above the silt.

 

Translating the scan:

Below are three images one of an Arial view of the area, two the original scan and three the interpreted scan.

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The numbers across the bottom of the scan are distance marks from the centerline of the boat.

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The numbers across the bottom of the scan are distance marks from the centerline of the boat.