Imaging Uxo Using Electrical Impedance Tomography

We report the results of tests where electrical impedance tomography (EIT) was used for<br>detecting and locating buried unexploded ordnance (UXO). The method relies on the<br>polarization induced at the boundary between soil and buried metal to produce a<br>measurable phase difference between the injected current and the measured voltage.<br>When natural sources of induced polarization are smaller than those due to buried metal<br>objects, then tomographs of impedance phase indicate regions were metal-soil<br>polarization may be present. Relatively large negative phases may indicate regions were<br>the buried UXO is located.<br>Unexploded ordnance is typically detected using magnetic surveys or conventional metal<br>detectors. These techniques provide limited information regarding the depth of burial of<br>potential targets and are adversely impacted by the presence of metal objects near the<br>surface, such as fences, building foundation, or buried utilities. The EIT method can<br>provide depth and position information on objects located below the surface, and can be<br>deployed around buildings, providing information regarding what lies beneath them.<br>Two controlled tests were performed at a field site containing UXO buried in known<br>locations. Both tests produced a phase anomaly of about 20 milliradians, which closely<br>matched the known location of buried UXO objects.