In 2024, GASCADE and Baker Hughes presented a comprehensive strain assessment of a 32-inch natural gas transmission pipeline crossing a land subsidence in a mining area in Germany. Following this study, Skipper NDT was commissioned in 2025 to re-inspect the same section using its magnetic-based geolocation and bending strain assessment (BSA) technologies. The objective was to verify the effectiveness of previous mitigation actions and to evaluate the potential of magnetic inspections as a complementary or alternative approach to in-line inspection (ILI) for geohazard management.
The inspection covered 384 m of line and was performed with Skipper NDT’s ATLAS ground-based platform, supported by UAV photogrammetry. The acquired magnetic data were processed through proprietary inversion algorithms to reconstruct the 3D centerline and compute bending strain profiles. These results were compared with historical IMU data from the 2019 ILI run across two subsidence zones previously analyzed in the 2025 PTC publication “Comprehensive Pipeline Strain Assessment for Management of Land Subsidence.”
The comparison revealed excellent geometric consistency, with horizontal deviations below 5 cm and vertical curvature differences within 0.1 %. The analysis confirmed that the mitigated sections remained strain-free, validating the effectiveness of the remediation works performed between 2020 and 2024. Additionally, the inspection identified a known buried crossing object (likely irrigation infrastructure), demonstrating the high sensitivity of magnetic mapping to surrounding ferromagnetic features.
This case study highlights the capability of UAV and ground magnetic inspections to provide precise, non-intrusive strain assessment and long-term verification of mitigation measures, supporting the development of continuous and cost-effective geohazard monitoring strategies for high-pressure transmission systems.