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56 be a ‘plus’ version for applications such as long layback tracking of towfish and touchdown monitoring of installations such as subsea cables and pipelines, and a standard version for more cost- effective USBL operations. KVH’s continuing r&d of photonic integrated chip (PIC) technology is entering the product phase, after two years of testing and development. The first shipments of FOGs and FOG- based IMUs with PICs incorporated are expected in the near future. “Testing the PIC technology has shown superior reliability and improved environmental survivability over competing technologies,” said Sean McCormack. The principle behind the technology is that the photonic chip’s design incorporates several passive functional FOG components, to enable geolocation and spatial orientation data with centimetre-level resolution and a 10x improvement in reliability compared with conventional FOG IMUs. The components designed into the PIC include a range of low-loss couplers that are used as a ring interferometer, a light source and detector transceiver, a high- propagation extinction ratio polariser, and high-efficiency fibre-connection mode size converters. It has other features for eliminating stray light. KVH’s current prototype photonic gyro IMU has an angular random walk of roughly 0.0097°/ √ h and a bias instability (or drift) value of 0.02°/h, enabling far more accurate navigation than typical IMUs of its size, weight and cost. The company anticipates the technology to have potential for upgrading navigation solutions such as the DSP-1760 FOG and GEO-FOG 3D INS, which are currently being used for marine-related research and exploration applications, including unmanned inspections, seafloor mapping and oil & gas surveys. The Fraunhofer Institute for Physical Measurement Techniques (Fraunhofer IPM) has developed a 3D Lidar system for inspecting, modelling and mapping underwater infrastructures. The Underwater Lidar (ULi) uses the time-of-flight optical method of distance measurement, in which a short laser pulse is emitted using a rotating mirror, then backscattered by the object being scanned and picked up by a detector. The time to return and the angle of the mirror give the position and distance of each measured point, with the mirror’s rotation enabling the generation of a 2D image. The motion of the UUV provides the third dimension for stitching 3D models together. Up to 40,000 points/s can be sampled over a scanning angle of 70-110°, at scanning frequencies of between 10 and 800 Hz. In typical operations, the ULi records 1000 points/m ² on objects up to 10 m away, at a resolution of 2 cm in the direction of movement and 5 cm along the scanning line. The system’s performance also improves with water quality – a range of up to 50 m with a precision of 6 mm is possible in clear water. Power consumption is about 170 W during normal operations, with a Class 3B laser used for underwater scanning (which self-adjusts to an eye-safe Class 1 in air). Design and integration can be customised through coordination between Fraunhofer IPM and UUV manufacturers. April/May 2020 | Unmanned Systems Technology Show update | Oceanology International 2020 Sonardyne’s Syrinx DVL PIC upgrade potential for KVH’s GEO-FOG 3D INS Fraunhofer IPM’s new underwater Lidar, the ULi