In-ground pipeline monitoring

A method for detecting contact with a pipeline in the ground, the method comprising:

• detecting an acoustic parameter associated with the pipeline using a first in-ground acoustic sensor in contact with the pipeline and transmitting a corresponding first input signal to a processor;
• detecting an acoustic parameter associated with the ground adjacent the pipeline using a second in-ground acoustic sensor spaced from both the pipeline and the first in-ground acoustic sensor and transmitting a corresponding second input signal to the processor;
• and comparing the first and second input signals in the processor in accordance with at least one signal comparison technique to produce a product signal as a function of the difference between the first and second input signal.

A method for detecting contact with an in-ground pipeline, the method comprising:

• receiving in a processor a first input signal from at least one first in-ground accelerometer and at least one second input signal from at least one associated second in-ground accelerometer, wherein the first in-ground accelerometer is in contact with an in-ground pipeline and the at least one associated second in-ground accelerometer is spaced from both the first in-ground sensor and the in-ground pipeline;
• and
• processing the first input signal and the at least one second input signal in the processor on at least one basis selected from the group consisting of time analysis, frequency analysis and a combination thereof to produce an output signal as a function of the difference between the first input signal and the second input signal.