Patent ID: 6084412
Filing Date: 2000-07-04
Classification: G01V

Abstract:
A method for locating an underground, conducting object comprising the step of reconstructing an electromagnetic (EM) field re-radiated by eddy currents induced in the underground, conducting object by illuminating the underground, conducting object with EM radiation from an above ground source, the reconstructing being over a horizontal plane in the ground using nearfield EM holography and the re-radiated EM field measured above or on the surface, the reconstructing step comprising the steps of:forming a spatial frequency spectrum using a Fourier transform in two dimensions and the measured re-radiated EM field;multiplying the spatial frequency spectrum by a propagation function for back propagating the re-radiated EM field in a vertical direction from above or on the ground to underground; andinverse Fourier transforming in two dimensions the result of the multiplying step to produce the reconstructed re-radiated EM field.