3D localization of non-metallic pipelines using rotating magnetic base stations

Abstract

Polyethylene (PE) pipelines are difficult to locate due to their non-magnetic and non-conductive properties. High-precision inertial navigation-based methods require pipeline shutdown, depressurization, and disconnection for internal detector deployment. Acoustic wave and electromagnetic field based methods require repeated lateral scanning using handheld instruments on the ground above the pipeline. This paper presents a blind positioning method for non-metallic pipelines based on extremely low-frequency dual rotating magnetic base stations and in-pipe Spherical Detector (SD). A position calculation method for magnetometers of the SD in arbitrary orientations relative to one single magnetic base station is proposed; and based on this, a pipeline positioning approach using dual magnetic base stations is developed. Scaled-down experiments are carried out and demonstrate that when the lateral distance is 1.29 m, the mean localization error in the horizontal and vertical directions are 6.23% and 6.15%. Due to the use of magnetic sources with frequency of several Hz, the obstruction by the wet soil does not reduce the accuracy of pipeline positioning. For 10 m deep PE pipeline in the field, the magnet should be increased by 10 times in three dimensions to achieve the same absolute positioning accuracy.