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

  • US 4,095,169 A
  • Filed: 03/09/1976
  • Issued: 06/13/1978
  • Est. Priority Date: 04/07/1975
  • Status: Expired due to Term
First Claim
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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 = HO 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 HO ;

    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.

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