Sea Technology

APR 2014

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

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40 st / April 2014 www.sea-technology.com rate of 40,000 points per second while traveling at 2 knots, processing the data in real time and building a 3D image on-the-fy. Approach Using software algorithms developed for lidar mounted on land-based and aerial vehicles, Lockheed Martin engi- neers produced amazing 3D models from point clouds gen- erated from the CodaOctopus (Edinburgh, Scotland) Echo- scope sonar. Lockheed Martin is now adapting the proven sonar software to process the SL2 lidar point clouds to gen- erate 3D models on-the-fy. Testing conducted by 3D at Depth and their partners has confrmed the SL2 product baseline performance while op- erating in a number of environments. Integrating the SL2 onto the Marlin is, therefore, less complex and diffcult. Tank Lab and Offshore Testing De-risking of offshore operations starts with a laboratory simulation that incorporates georegistered 3D models of the subsea scene and bathymetry, vehicle motion and trajectory, simulated models of the actual laser performance (transmis- sion and scattering) in the seawater medium, simulated performance of the SL2 3D lidar, and the onboard signal processing used by the Marlin. 3D at Depth and their partners have conducted tests us- ing a frst-generation product, INSCAN, against varying tar- gets common to the subsea oil feld, including sample well- head valve panels, and an actual pipeline end termination deployed in a deepwater Gulf of Mexico feld. Based on successful testing of the INSCAN sensor in con- trolled conditions and subsequent feld use, 3D at Depth engineered the SL2 model to match Lockheed Martin's specifcations for use on the Marlin AUV. A series of laboratory simulation test cases was devel- oped to allow the engineers to examine the entire system's performance across a range of varying parameters. Each test ing feld. When mounted to an ROV, the sensors must be stabilized by the ROV fxing itself to a stable structure and/ or sitting on the seabed while measurements are made. Both of these techniques produce limited, incomplete views of the scene, resulting in limited information to the client. This technique also requires multiple repositioning of the sensor and signifcant post-processing to generate a fnal image. Lockheed Martin's Marlin not only carries the sensors, but also autonomously interacts with the sensors and the vehicle's navigation and control system to produce high- quality, motion-compensated 3D models within minutes of retrieving the vehicle to the surface. Three-D imaging "on- the-fy" enables users to collect a whole perspective view of the subsea feld with accurate 3D models generated for every structure imaged over the course of a data collection mission. These models are not limited to the scanning feld of view of a tripod-mounted sensor, and Lockheed Martin's Feature Based Navigation system produces models that are accurate to millimeters or centimeters, depending on the 3D sensor employed. Lockheed Martin and 3D at Depth LLC (Boulder, Colo- rado) are incorporating the SL2 3D lidar onto the proven Marlin AUV, resulting in a transformational capability to produce georegistered 3D images of subsea equipment on- the-fy with millimeter resolution. Challenge Given the precision placement and small diameter of a laser's spot size, the high scan rate, and potential distortion of an image resulting from sensor motion, a tight coupling of the lidar sensor with the Marlin AUV's motion is required to produce accurate 3D models. Our team's goal is to collect high-precision georegistered image points underwater at a (Top) Composite image generated by the INSCAN lidar of a deepwater pipeline end termination. (Right) Laser scan of a subsea well tree. (Bottom) Composite laser/video im- age of a subsea manifold. AprilBook.indd 40 4/7/14 12:19 PM

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