Automated Anomaly Picking From Broadband Electromagnetic Data In Uxo Survey

We present automated anomaly-picking methods for detecting unexploded ordnance from<br>broadband electromagnetic data. Using data consisting of in-phase and quadrature responses at multiple<br>(typically 10) frequencies, a “detector function” attempts to detect all metal objects but to suppress false<br>alarms caused by geology, variations in sensor height, and sensor motions in the earth’s magnetic field.<br>Promising detector functions considered here are (1) the sum of all quadrature responses, Q-sum,<br>(2) the sum of all differences among the in-phase or quadrature components, I- or Q-spread, (3) the sum<br>of the I- and Q-spreads, T-spread, (4) the weighted total apparent conductivity, TAC, from all<br>frequencies, and (5) the apparent magnetic susceptibility, AMS, derived from the lowest frequency of a<br>survey. These detector functions favor metallic objects and are relatively insensitive to geologic<br>variations and motion-induced noise that are common with a handheld sensor or a cart-mounted sensor<br>in rough terrain. We discuss the properties of these detector functions, apply them to field data from two<br>sites, and compare the results with limited ground truths.