Sea Technology

JUN 2017

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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10 st / June 2017 www.sea-technology.com extending the array length. This results in the ability to use lower frequencies to attain equivalent or higher resolutions, and at much longer ranges. SAS systems are used by navies for mine sweeping but are also commercially available from many companies and are employed for civilian applications such as pipeline inspection, search and recovery, underwa- ter geology, and archaeology. T he development of technologies for reacquisition and identifica- tion (RI) of risks posed by underwa- ter objects has received much at- tention over the past few decades. Hazards such as unexploded ord- nance (UXO) and sea mines have been a focal point for underwater RI research efforts due to the danger they pose to humans, trade and the environment. The ocean environ- ment and hydrodynamic activity inherent in maritime environments can have a significant effect on the success or failure of various RI technologies; targets can become buried or partially buried, and wa- ter conditions, such as clarity, can make certain technologies difficult or impossible to use. Furthermore, in some cases, the nature of the target may make close range iden- tification hazardous or impractical. For these reasons, acoustic technol- ogies are often used for RI. Many acoustic technologies ex- ist for high-resolution reacquisition and identification. Side scan and forward-looking sonars can provide near instantaneous feedback in many cases, and have found a large number of applications in both com- mercial and naval situations where high-resolution acoustic imaging is necessary. One of the primary shortcomings of these technologies is that resolution is limited by the physi- cal length of the array and decreases with range. Very high- resolution systems compensate by using high frequencies, however this comes with the penalty of increased attenua- tion, reducing the practical range of these systems. Synthetic aperture sonar (SAS), in contrast, is a technol- ogy that overcomes the resolution constraints imposed by physical array length by coherently processing the backscat- tered signals as the array travels through the water, virtually 3D Volumetric Sonar Imaging For Identification Missions Advanced 3D Imaging on Unmanned Systems to ID Objects on Seabed By Dr. Jermaine L. Kennedy • Dr. Timothy M. Marston CSAS volume imagery for a lobster pot. A) is the 3D rendered image; B) is a cutaway showing one of the trap inlets; C) is a horizontal cutaway through the inlets, bait spike and net; and D) shows the bait spike. (Image Credit: U.S. Navy)

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