A pipeline inspection and defect
mapping system includes a pig having an
inertial measurement unit and a pipeline inspection unit for recording pig location and defect detection events, each
record time-stamped by a highly precise onboard
clock. The
system also includes several magloggers at precisely known locations along the pipeline, each containing a fluxgate
magnetometer for detecting the passage of the pig along the pipeline and further containing a highly precise
clock synchronized with the
clock in the pig. The locations of the various magloggers are known in a north / east / down coordinate
system through a differential global positioning
satellite process. Finally, a postprocessing off-line computer
system receives downloaded maglogger, inertial measurement, and
odometer data and through the use of several Kalman filters, derives the location of the detected defects in the north / east / down coordinate frame. Consequently, a task of identifying sites for repair activity is much simplified.