Method for locating discontinuities in the electrical conductivity of the sub-soil using a plurality of magnetic detectors in a predetermined spatial arrangement

Claim 1

A method for obtaining an indication of the electro-magnetic characteristics of the sub-soil underlying a ground surface comprising the steps of: a. placing on the ground in a substantially horizontal plane at least four directional magnetic field detectors in two sets wherein each set comprises a spaced pair of detectors oriented in the same direction with the detectors of each set oriented at right angles to the detectors of the other set; b. simultaneously monitoring the output signal from each of said detectors over a period of time, each of said output signals being made up of a plurality of spectral components; c. electronically processing said output signals by characterizing each of said spectral components as being of the form H = H O e t/τ where t is time and τ is a time-constant to derive for each of said spectral components in each of said output signals a magnetic field amplitude value H O ; d. combining amplitude values corresponding to the same spectral component from each of said output signals to obtain a non-variable physical parameter associated with said spectral component which is related to the electrical conductivity of the sub-soil beneath the detectors and is independent of any phase shift existing between the output signals from the pair of detectors in each of said sets.

Claim 2

A method for obtaining an indication of the electro-magnetic characteristics of the sub-soil underlying a ground surface comprising the steps of: a. placing on the ground in a substantially horizontal plane at least four directional magnetic field detectors in two sets wherein each set comprises a spaced pair of detectors oriented in the same direction with the detectors of each set oriented at right angles to the detectors of the other set; b. simultaneously monitoring the output signal from each of said detectors over a period of time, each of said output signals being made up of a plurality of spectral components; c. electronically processing said output signals by characterizing each of said spectral components as being of the form H = H O e t/τ where t is time and τ is a time-constant to derive for each of said spectral components in each of said output signals a magnetic field amplitude value H O ; d. combining amplitude values corresponding to the same spectral component from each of said output signals to obtain a non-variable physical parameter associated with said spectral component which is related to the electrical conductivity of the sub-soil beneath the detectors and is independent of any phase shift existing between the output signals from the pair of detectors in each of said sets.

Claim 12

A method for obtaining an indication of electro-magnetic characteristics of a sub-soil underlying a ground surface comprising the steps of: a. defining with respect to a reference point on the ground surface three mutually perpendicular X, Y and Z directions, directions X and Y being in a generally horizontal plane and direction Z being generally transverse to the ground surface; b. providing at least four directional magnetic field detectors; c. positioning a first and a second detector relative to the ground surface area and orienting said first and second detectors in X and Y directions, respectively; d. positioning a third and a fourth detector relative to the ground surface area in spaced-apart and substantially parallel relationship with respect to the first and second detectors, respectively, and orienting the third and fourth detectors in substantially the same direction as the first and second detectors, respectively; e. generating with each of the detectors output signals responsive to a magnetic field of the sub-soil underlying the detector, each of said output signals further comprising a plurality of spectral components; f. electronically processing each of said output signals by characterizing each of said spectral components as being of real increasing exponential form to derive for each of said spectral components of each of said output signals an amplitude value; g. combining amplitude values associated with corresponding spectral components from each of said output signals to produce a non-variable physical parameter which is indicative of the electrical conductivity of the sub-soil beneath said detectors.

Claim 13

A method for obtaining an indication of electro-magnetic characteristics of a sub-soil underlying a ground surface comprising the steps of: a. defining with respect to a reference point on the ground surface three mutually perpendicular X, Y and Z directions, directions X and Y being in a generally horizontal plane and direction Z being generally transverse to the ground surface; b. providing at least four directional magnetic field detectors; c. positioning a first and a second detector relative to the ground surface area and orienting said first and second detectors in X and Y directions, respectively; d. positioning a third and a fourth detector relative to the ground surface area in spaced-apart and substantially parallel relationship with respect to the first and second detectors, respectively, and orienting the third and fourth detectors in substantially the same direction as the first and second detectors, respectively; e. generating with each of the detectors output signals responsive to a magnetic field of the sub-soil underlying the detector, each of said output signals further comprising a plurality of spectral components; f. electronically processing each of said output signals by characterizing each of said spectral components as being of real increasing exponential form to derive for each of said spectral components of each of said output signals an amplitude value; g. combining amplitude values associated with corresponding spectral components from each of said output signals to produce a non-variable physical parameter which is indicative of the electrical conductivity of the sub-soil beneath said detectors.