Method for detecting underground tunnels

A method for detecting tunnels within an area comprising the steps of:

• providing, with one or more of a gradiometer and an accelerometer, horizontal tensor gravity gradients for the area;
• calculating, using the gradiometer, a plurality of gravity gradient vector field pairs from the horizontal tensor gravity gradients, each gravity gradient vector field pair including one gravity gradient vector field and a respective orthogonal gravity gradient vector field;
• performing a probability tomography analysis for source pole occurrence probability (SPOP) on each of said one and said respective orthogonal gravity gradient vector fields of each of said plurality of gravity gradient vector field pairs;
• detecting dipolar points and polar source points in each of said one and respective orthogonal gravity gradient vector fields for each gravity gradient vector field pair;
• and
• identifying said polar source points that are present in one but not in both of said one gravity gradient vector field and said respective orthogonal gravity gradient vector field for each gravity gradient vector field pair to thereby detect the tunnels;
• wherein the step of detecting dipolar points and polar source points further comprises the step of segregating said polar source points from said dipolar points in each of said one and respective orthogonal gravity gradient vector fields.

A method for detecting tunnels within an area comprising the steps of:

• calculating, using a gradiometer, a plurality of gravity gradient vector field pairs for the area, each gravity gradient vector field pair comprising two vector fields orthogonal to one another, obtained using one or more of the gradiometer and an accelerometer;
• performing a probability tomography analysis for source pole occurrence probability (SPOP) on each of said plurality of gravity gradient vector field pairs;
• detecting dipolar points and polar source points in each of said gravity gradient vector field pair;
• and
• identifying said polar source points that are present in one but not in both of said two vector fields for each of said plurality of gravity gradient vector field pairs to thereby detect the tunnels;
• wherein the step of calculating a plurality of gravity gradient vector field pairs is comprised of the steps of:
• selecting first and second gradient directions perpendicular to each other, said first gradient direction aligned along azimuth between 0 degrees to 90 degrees;
• calculating said gravity gradient vector fields based on said first and second gradient directions;
• and
• repeating the calculations for said gravity gradient vector field pairs at subsequent incremental first and second gradient directions ranging from 0 degrees to 90 degrees.