AIP Digital Archive
Recently, it becomes more important to locate the complex piping patterns such as tee, bend, riser, and the others with high accuracy for maintenance and protection of city gas pipelines. Hence, we have developed a new pipe locator system for imaging the complex underground pipelines using magnetic remote sensing techniques. The main framework of this development is the application of the pattern recognition of the magnetic field distribution to the location of buried pipelines in urban areas. The first step for imaging the complex pipelines is to measure the three-dimensional magnetic field distribution with high accuracy which is generated by the passage of the alternating signal current through buried pipeline. For this purpose a portable trolley unit which is capable of scanning the ground to collect data, the 10 three-axes coil sensors with a sensitivity of 1 μG which are aligned in the unit, and a filter system using a FFT signal processor which eliminates urban magnetic noise as high as 10 mG in some cases, were developed. The second step is to process the magnetic field distribution data, to extract the feature of the underground pipeline using the contour diagram and the three-dimensional drawing of the magnetic field, and to identify the complex piping patterns. Further, we recognized that a nonlinear least-square method algorithm for calculation of the pipeline's position was useful to improve the location accuracy.
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