Sea Technology

NOV 2017

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Page 12 of 53 November 2017 / st 11 curacy in an MCM environment. Integrated into the Klein 5900 sonar architecture is a swath bathymetric sonar. This sonar uses advanced phase delay signal processing to pro- duce co-registered topography of the seabed out to the full swath extent of the side scan sonar. Side-looking sonars that do not have the ability to per- form bathymetric measurements must assume a locally flat bottom when measuring the location of seabed targets. This can result in target position errors on the order of meters when surveying over sloped bottoms. This added seabed topographic mapping capability is an additional advantage to performing missions involving shallow-water, rapid area assessment. receive subarrays on each side. Each sound sam- ple from each element is recorded and stored in memory. A software process subsequently takes into account position information, motion sensor and user's parameters to retrieve the appropriate sound samples from the sound memory to com- pose a synthetic image. Dynamic beam steering image stabilization technique is used to remove artifacts caused by tow vehicle motion that would otherwise blur seabed images, especially at longer range where the effects due to angular perturbations are more pronounced. This is a marked improvement over the 5000 family, which produces succes- sive beams perpendicular to the tow body and is more susceptible to compressed or elongated images due to excessive tow fish yaw. Image stabilization helps to ef- fectively extend the range of the sonar by minimizing this distortion. By the laws of physics, sonar waves reflected from a tar- get have different radii depending on the distance of the tar- get. When the operator sets the system, for example, on 75 m, the 5900 software delays each sound sample to adapt to the corresponding radius. At 100 m, the software computes a larger radius. The dynamic focusing, i.e., computing the delay of each sound sample, is one of the contributing fac- tors for the 5900 crisp imagery. The next step in the process of image optimization is to take into account the fluctuations in the heading of the so- nar body. Motion sensor information (heading, pitch, roll and yaw) are fed into the 5900 algorithms to create synthet- ic beams pointing orthogonally to the course over ground, as opposed to orthogonally to the towfish heading which is intrinsically unsteady in operational conditions. The 5900 has several options designed to increase efficiency and ac- (Top) Klein 5900 in the automated launch and recovery cradle. (Bottom) Elbit Seagull with integrated Klein 5900 mobilized at Zeebrugge Naval Base.

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