Underwater Laser Scanning with QINSy
Recently QPS was involved in a subsea laser scanning test, the objective of which was to create the point cloud of scanned structures, on-the-fly. QINSy was interfaced directly to the ROV sensors (high-end INS, Doppler) and the underwater laser scanner. For this the ULS-500 was used, a high resolution underwater laser scanner from 2G Robotics. The laser data was corrected for ROV attitude in real-time and geo-referenced using INS position updates aided by Doppler.
The ideal application for an underwater laser scanner involves short-range, high-detail measurements of specific locations on an asset. Such applications include damage assessment, archaeological documentation, and as-built documentation. Although the technique for subsea laser scanning differs from terrestrial laser scanning, the achieved resolution remains the same. Unlike traditional acoustic techniques like multibeam or side scan sonar, the resolution of scanned structures will be much higher. In addition to that, using QINSy, obligatory sound-velocity correction or ray tracing will be unnecessary. What you hit is what you get! You should not forget that underwater laser scanning results is also dependent on external variables such as local water conditions like silt, mud, penetrated surface light, etc. The scanned distance is also limited to maximum 5 to 10 meters. However, the details of the scanned objects underwater are incredible, especially in combination with color-coding based on the reported intensity values.
Main challenge with subsea laser scanning projects will be absolute positioning, even more so than with high-resolution multibeam surveys.
Notice the ROV path (in green), demonstrating how it hovered around the underwater structure while undertaking the scanning.