Soil /Metal Discrimination Analysis of EM 61 Mk Ii Time Decay Response at former Camp Croft, Sc

Electromagnetic (EM) data recently acquired for a munitions detection project, processed using<br>standard Geosoft Oasis Montaj methods and analyzed in profile, produced more than 1000 targets per<br>acre, far more than the number predicted by prior clearance in adjacent areas.<br>Standard data processing was expanded to incorporate a new technique developed by<br>Geophysical Associates (GPA) for dealing with magnetic soils in Hawaii. This technique is GPA<br>Soil_Metal Discrimination Analysis, based on statistical Chi-squared discrimination analysis of the<br>difference of time decay response across the four EM61 Mk II channels from that of soil and rocks.<br>Preliminary results show that GPA Soil_Metal Discrimination Analysis reduced the number of<br>targets per acre by approximately 80%. Most of the GPA-derived targets yielded significant metal<br>items.<br>As in other geophysical approaches, there remains some residual risk that not all buried<br>munitions will be detected. Some metallic objects, at certain orientations, have decays similar to<br>magnetic soil and will yield corresponding Chi-squared results.