Research on Above Ground Marker System of Pipeline Internal Inspection Instrument Based on Geophone Array

The above ground marker system (AGM) is an important part of pipeline internal inspection instrument, which can reduce the mileage error and improve the positioning precision. A AGM based on geophone array was proposed aiming at increasing depth problem of the pipeline. It can record and amplify the sound of an approaching pipeline pig´s cups striking the welds of a pipe to an easily discernible level. The seismic signals generated by the different targets around the pipeline were gathered. These signals were pre-processed and the targets features were extracted, by the EMD (Empirical Mode Decomposition) based signal feature extraction method, to identify different the targets. After estimating the time difference of signal arrival on different sensors by cross correlation-phase transform (GCC-PHAT) method , the the spacial location of internal inspection instrument can be realized, according to the time difference and relative position between the sensor array and the pipe. The proposed method above was verified through the outside simulated experiments and data analysis.