Patent Document ID: 10061044
Application ID: 15094549
Patent Flag: 1

Claim One:
1. A method of detecting subsurface tunnels, the method comprising: measuring air pressure continually in time with a first sensor positioned above or below ground to generate a first air pressure signal; measuring air pressure continually in time with a second sensor positioned at a depth relative to a surface of the earth and positioned at a greater depth below the surface of the earth than the first sensor to generate a second air pressure signal; generating a third air pressure signal using a numerical model that employs the first air pressure signal as input to produce an optimal approximation of the second air pressure signal, the accuracy of such approximation being optimized by systematic adjustment of model input parameters that represent the effects of the permeability of the earth and the depth of the second sensor on the difference of the second air pressure signal from the first air pressure signal; and detecting the introduction of a subsurface tunnel proximal to the second sensor based on a change in the accuracy with which the third air pressure signal approximates the second air pressure signal over subsequent time windows.