Several concepts are discussed for sensing the position of the pipeline externally in order to detect changes in its position and relate them to strains. These include the use of radar, sonar, eddy current, and the electromagnetic device mentioned previously. In each case, the need exists to demonstrate adequate sensitivity and to develop a vehicle to carry the device along the pipeline. The technique with perhaps the greatest potential for most completely meeting the needs of the industry is fiber optics. Both the location of the strain along the cable and the magnitude of the strain change should be detectable.
Many practical problems face developers of the fiber-optics approach.
Of the various non-conventional techniques, it would seem that three are particularly worthy of continuing attention by the industry. One is the inertial guidance pig which is said to be near commercial availability. When it does in fact become available, one or more companies may find it worthwhile to try it. A second concept of considerable interest is fiber optics. While this technique faces formidable technological barriers, it would potentially meet more of the industry's requirements than any of the competing schemes.