Electromagnetic Methods for UXO Discrimination

Abstract

The subsurface remote-sensing technology currently used in the United States for UXO decontamination is relatively crude, consisting of DC (static) magnetometry. Ultrawideband electromagnetic induction (EMI) is emerging as a technology with reasonable discrimination potential. EMI devices operate in the magneto-quasistatic (MQS) band, usually between tens of Hz and perhaps a couple hundred kHz, and engage a substantially different phenomenology than that of wave electromagnetics. Over the relevant space scales, soil, fresh water, and rock are effectively lossless in the MQS regime, which encourages EMI application.Here we review the relevant EMI physics and phenomenology and then discuss state-of-the-art EMI discrimination methods like the Standardized Excitation Approach (SEA). This can be used in signal matching to decide if an unseen target belongs to a catalogued set. It can also quickly provide many examples of realistic input to train statistical learning algorithms such as Support Vector Machines (SVM). SVMs can also use SEA parameters themselves as discriminators. Most realistic UXO-sensing scenarios are clutter limited. We examine computational upward continuation as a clutter-mitigation strategy with a rational physical basis.