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www.sea-technology.com June 2017 / st 15 T o assist bomb disposal divers in their operations in coastal and port areas, RTsys of Caudan, France, specializing in under- water acoustic systems, has de- signed a new handheld sonar: the SonaDive. The fact that it is nonmagnetic means that it can detect and locate different types of submerged explosives as div- ers remain at a safe distance. The device can also be used to search for shipwrecks, bodies and debris. Use of the sonar sys- tem in the civilian sector facili- tates seabed observation (aquat- ic plant habitats, coral reefs, port areas, etc.) for the needs of sci- entific research and monitoring of the marine environment. A range of functions come as standard, providing the user with a comprehensive expe- rience, including compatible communication, navigation and visualization systems that are optimally integrated into the handheld sonar. Advanced Navigation System SonaDive has an advanced, efficient and highly accurate navigation system, which is rare for a small device. Standard functions include a navigation unit, GPS, immersion sensor and Doppler velocity log (DVL). Programmed using a GPS located on the surface, the device can maintain its position with an accuracy of 5 to 10 m after swimming more than 500 m. The GPS can also be turned toward the surface dur- ing an operation. As such, divers have a unique tool at their disposal that enables them, on the one hand, to be aware of their exact position at all times and, on the other hand, to go to points of interest predetermined and programmed before the operation without requiring prior mark up. With SonaD- ive, operations can be programmed, recorded and post-pro- cessed. Users can also add points of interest to be explored later, or carry out monitoring over an extended period of time by reprogramming the same operation at various intervals. The diver's position is constantly displayed on the background chart where movements are shown. Users can view a programmed operation and the ground covered. A combination of screen views is available to the diver, enabling the diver to view his or her posi- tion while also viewing images from the sonar camera. The charts are loaded by the user, in S57, S63 or GeoTIFF for- mat, and can therefore be nautical charts or charts personal- ized with additional information already known by the user (nature of the seabed, state of the ecosystem, coastal envi- ronment characteristics, etc.). Communication Between Divers This handheld sonar device has integrated underwater acoustic communication functions that can send messages over distances up to 2,000 m. Divers have a set of short prerecorded messages (SMS type) available, which they can personalize before an operation. The device comes with a waterproof tablet that is used to program the operations and replay them later. Once connected to a transmission case, the SonaDive can also be used as a means of communica- tion between the dive boat and the divers during operations. Scanning in High Resolution In order to observe the seabed, SonaDive can be fitted with two detection systems using interchangeable Teledyne BlueView acoustic cameras, depending on user needs: a 450-kHz sonar for distant (up to 300 m) detection and a high-resolution sonar for close-range work. The latter dual- Handheld Sonar System For Divers Navigation, Communication, Visualization in One Sonar Device By Dominique Ropert • Raphaël Bourdon • Alice Vettoretti A diver using the SonaDive device. The sys- tem includes a gradiometer, which surpasses the sonar's capability and can be removed if desired by the user. (Photo Credit: Creocean)