A case study of magnetic gradient tensor invariants applied to the UXO problem

Data were gathered at the Yuma Proving Ground (YPG) to demonstrate the effectiveness of the Tensor Magnetic Gradiometer System (TMGS) for the detection of buried unexploded ordnance (UXO). After a rigorous reduction of the TMGS data, the magnetic gradient tensor was calculated. From the gradient tensor values, the tensor invariants were determined. By comparison of known target locations and Very Early Time Electromagnetic (VETEM) data to the mapped invariants, it was found that the invariants do an excellent job delineating UXO targets and that their correctly positioned unipolar characteristic make them easier to compare to electromagnetic (EM) results than total field magnetic measurements.