Robert E. Bracken

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

Summary: 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.

Field Experiments With the Tensor Magnetic Gradiometer System For UXO Surveys: a Case History

Summary: In March, 2003, the U.S. Geological Survey (USGS) conducted proof-of-principle tests of the tensor magnetic gradiometer system (TMGS) at the Strategic Environmental Research and Development Program’s (SERDP) Unexploded Ordnance (UXO) Standardized Test Site at the Yuma Proving Ground (YPG), Arizona. The objective of these tests was to assess the potential of this system for UXO applications and to help us formulate design parameters for an improved tensor magnetic gradiometer system designed specifically for UXO. Although the current TMGS was not designed with UXO applications in mind, it detected the majority of the buried targets in the Calibration Area at YPG. Its performance rivaled that of the cesium vapor companion system, and it showed true tensor gradiometric performance over a selected target.