Strapdown inertial systems for pipeline navigation

Inspection and fault identification of pipelines is commonly carried out by instrumented vehicles propelled by product flow through the pipeline. The author describes an investigation into means of improving the inspection vehicle´s positioning capability by the inclusion of an INS onboard the vehicle. A software package to simulate a strapdown inertial survey has been written, coded and tested. The simulation gives a useful insight into the behaviour of a strapdown inertial system and into the effects of the various error sources. Tests have been carried out for a fifteen kilometre south-north traverse over a period of 100 minutes. Preliminary results indicate that the available odometer data can be integrated to a low-grade INS to give a position error precision of the order of twenty metres. More frequent position fixes should improve this accuracy to the required half pipe length accuracy. By using higher quality velocity measurements and more frequent position fixes, the positioning precision is expected to achieve the sub-metre level