LAUSR

This article introduces a new triaxial magnetic field gradiometer to detect, locate, and map underground metallic utilities, such as a thin wires, railroad tracks, and pipes. The system couples a primary electric field along target’s elongation to maximize excited linear electric (i.e., non-solenoidal) currents and uses magnetic field induction sensing (i.e., Faradays induction law) to measure secondary magnetic fields. First, theoretical and numerical studies are presented for the broadband electromagnetic response from long thin wires buried in a conducting soil at varying depths. Second, numerical calculations are validated against experimental data. Favorable comparisons between model and measured data are illustrated for wires subjected to both plane wave excitation, originating from a 1.4-MHz amplitude modulation (AM) station as well as local excitation. Third, forward and inverse electromagnetic models are applied to electromagnetic gradiometer (EMG) field data to extract the wire’s burial depths from different survey track data, showing good agreement for wire depths from 0 to ~6 m. Finally, multiwire location and orientation are extracted from the triaxial vector gradiometer dataset. These results illustrate the applicability of linear current sensing for detecting, locating, and mapping deep underground metallic infrastructures, such as wires, railroad tracks, and pipes.