Pipeline operators need to 3D-geolocalize their buried pipelines for two main reasons: to update their network’s Geographic Information System and for safety considerations, in particular, to determine the depth of cover. The latter is a key parameter to ensure the network’s protection in case of third-party interferences. Several methods are available for pipeline geolocalization, such as electromagnetism, in particular, radio-frequency techniques and ground-penetrating radar. They all entail either specific soil conditions or are manual (prone to human error) and time-consuming.
Skipper NDT has developed a proprietary method to provide precise and continuous coordinates (longitude, latitude) and depth of cover of buried pipelines, using large standoff magnetometry (LSM). The patented hardware measures the magnetic field above the pipeline, using fluxgate three-component magnetometers and a GNSS. To determine a precise position, an algorithm performs 2D and 3D magnetic data inversions along the road map for automatic detection and georeferencing. The performances of Skipper NDT’s detections were tested under field conditions and compared to land surveyor’s results, thanks to a collaboration with the French gas operator Teréga. Compared to the 3D reference, the accuracy is at least 0.2 m for 90% of measured data.
Keywords: Magnetic Inverse Problem, Magnetic Map, Fluxgate Magnetometer, Geographic Information System, Depth of Cover, Non-Destructive Testing.