A 3D Localization Approach for Subsea Pipelines Using a Spherical Detector

A 3D localization approach for subsea pipelines is proposed using an internal mobile spherical detector without any external auxiliary location measurements. The process of solving for the pipeline orientation using the magnetic field and acceleration measured simultaneously by the spherical detector is formulated in the rotating sensor frame. Specifically, when the frames of the accelerometer and magnetometer are identical, the measured acceleration can be used to construct the rotation matrix to map the rotating sensor frame to the stationary pipe frame. This transformation by the rotation matrix can be applied to the measured rotating magnetic field to solve the orientation equations. The rolling frequency of the detector is used to calculate the spherical detector's velocity and mileage within the pipeline. The approach and the system have been successfully applied in a 30-km long oil pipeline. After calibration by aligning the calculated and actual pipeline ends through 3D rotation, an absolute localization error of 1.2 km is achieved. This result is promising as an initial model for future use with external measurements.