112 Sidescan sonar One of the optional sensors is an 1800 kHz, 600 m-capable ARC Scout Mk II sidescan sonar from Marine Sonic. It comes with a pair of transducers for mounting on the sides of the vehicle and a single small box of processing electronics for installation inside the pressure hull. A Barracuda on display at the Ocean Business event in April in Southampton, UK, was fitted with a pair of mock-up transducers, which are a little over 9 in long, and which the company fitted in order to test their effects on the vehicle’s stability and drag characteristics. Customer Ocean Builders is due to take delivery of the first Barracuda to be equipped with this sonar. Daum admits that the sonar transducers, which sit a little way from the hull, look rather like grab handles, even though they are not intended to be used to pick the AUV up. However, they are quite sturdy and are screwed into inserts in the hull. “Although I wouldn’t recommend you do this every time, if you were to pick it up that way I don’t think you would break them off,” Daum says. “Also, if you did happen to break one off you could put the inserts back in with regular marine-grade epoxy, and you could do that repair on the boat so you wouldn’t have much downtime.” The ARC Scout Mk II comes in single and dual-frequency forms covering six centre frequencies between 150 kHz and 1800 kHz. In 1800 kHz form, it has a maximum range of 25 m from either side and an along-track resolution of 5 cm, enabling it to create highly detailed images of objects on the seabed. Lidar and RGB camera Another sensor system under development for the Barracuda is an underwater Lidar system combined with an RGB camera. Together, these sensors are designed to create 3D images in colour of underwater objects. The RGB camera is a high dynamic range 24 MP scientific sensor, which provides a colour overlay on the 3D point cloud generated by the Lidar. “The Lidar we are developing has a blue-green laser, generates about 300,000 points per second and has RGB capabilities of its own,” according to Larson. “The separate RGB camera is downward-facing, and we will be taking about four images per second with it. Once we have collected the point cloud and processed it into a topology, we can overlay the RGB images and get, more or less, a photo of the bottom in 3D.” “The system is a true colour Lidar that will capture about four images per second,” he explains. “The sensor package is being provided by Beam Sea Associates and SEE Monster Vision Solutions. “The system provides colour-corrected 3D point cloud datasets at a subcentimetre spatial resolution. Once the data has been collected and processed, we will have a photorealistic 3D image of the bottom. The end product will be useful for applications such as subsea mapping, coral reef surveys and obstacle detection.” Together with these two companies, Tampa is working to miniaturise an existing system to fit inside the Barracuda. All the companies are small businesses located in Florida, and this project is the subject of a US Government Small Business Innovation Research programme from the US National Oceanographic and the Atmospheric Administration. Daum reports that the team is now assembling the prototype, which should be ready for testing by this autumn, with the full Lidar capability expected to be available in 2025 or 2026. Operational practicalities Operable by one person, the Barracuda is provided with an open source user interface based on Mission Planner for loading missions into the autopilot. Comms with the Nvidia GPU are through a network connection and command line interface. August/September 2023 | Uncrewed Systems Technology Another optional sensor is the Lidar installation that works with an RGB camera to produce colour 3D imagery of underwater objects
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