Abstract: A system for detecting the 3D shape of underground pipelines, especially in trenchless construction process, has been developed. This pipeline detecting system is composed of a gravity accelerometer, a magnetometer, a distance measuring mechanism and a control circuit. Driven in the pipe, the sensors measure the direction angle and distance at certain points. The 3D coordinates and the shape of the pipe are then obtained. Measurement repetitiveness of the pipe position is within ±5%.

Key words: gravity accelerometer, magnetometer, pipeline detecting system, trenchless