Zero crossing correlation to detect underground leak

Underground leak detection in pipe carrying water is extremely important and very difficult at the same time. Many techniques have been reported in literature to locate those leaks. But signal processing may be the most popular, in particular cross correlation technique. Cross correlation is used to measure the strength of similarity between two signals at a particular delay and the position where this strength occurs. But in the case of leakage, only the location where the peak of the correlation occurs is of interest. This has led to the current study. When a leak occurs, two signals are generated, one upstream and one downstream. Those two signals are picked up by two transmitters installed at the two ends of the pipe. The picked signals are modified using zero crossing detector. Those crossings are timed and used to estimated where the peak occurs. This time represents the delay between the signals reaching the transmitters. Knowing the time delay, the total length of the pipe as well as the speed of the propagated signal, the estimated location of the leak could be calculated.