Abstract: A pipeline monitoring system for determining profile, ovality and displacement of oil, gas and products pipelines. The system comprises one or more pig carriers housing a plurality of sensors including a strapdown inertial measurement system, a secondary sonar measurement system, digital recorder, weld detector and odometer. The inertial measurement system detects primary acceleration and orientation data of the monitoring system within a pipeline and the secondary system generates redundant data for verifying the acceleration orientation information provided by the inertial system. The digital recorder records all of the information generated by the various measurement systems and sensors for post ash processing analysis to determine the aforementioned features of profile, ovality and displacement of pipelines.