The introduction of AUVs in pipeline inspection can provide great benefits, both in terms of time and cost savings, and increased data quality. AUVs can operate at higher speed than ROVs, they can operate without being followed by a large survey vessel, and their smooth trajectory allows higher sensor data quality than what most ROVs can collect. With partial funding from the Research Council of Norway, Kongsberg Maritime and FFI are developing a new concept for AUV based pipeline inspection. Using the latest generation HUGIN 1000 AUV, around 60 km of pipe can be surveyed per day, with high-resolution SAS imagery and bathymetry covering the pipeline and a wide swath around it, plus optical imagery and multibeam bathymetry from low altitude directly over the pipe. The standard concept calls for two passes of the pipeline, First, the AUV surveys the pipeline with HISAS at a distance of 50-100 metres and a speed of 4 knots. The pipeline is detected and tracked in real time. This information is used to actively control the AUV position, but also to update the estimate of the pipeline position, and information about buried sections of pipe. After up to 8 hours of surveying in this manner, the AUV turns around and returns at low altitude directly above the pipeline. This provides high quality data from a multibeam echo sounder (EM 3002 or EM 2040) and an optical camera. The updated pipeline map is used to assist the real-time tracking, which is based on multibeam data. As any buried sections will be known from the first part of the survey, there is no need to enter a time-consuming search phase if the pipeline cannot be found - the system will just continue towards the position where the pipe resurfaced. Initial demonstrations of this system are planned for early 2011.
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