Objective

First time channel of synthetic data generated for a Stokes mortar buried in a two-layer background.

Magnetic and electromagnetic (EM) surveys are two effective geophysical techniques for unexploded ordnance (UXO) investigations. Both have a well-documented ability to locate UXO but are prone to excessive false alarms, which significantly increases the cost of cleanup. For instance, at some sites up to 75 percent of excavated items are non-UXO. The key to reducing these false alarms is the development of algorithms that can discriminate between an intact UXO and other items such as scrap metal or geological features. Recent developments have enabled the recovery of dipole or ellipsoidal parameters through inversion of magnetic data. Additionally, frequency and time-domain electromagnetic measurements can be inverted to recover parameters in reduced modeling formulations. These recovered parameters can then be used to discriminate between UXO and other items. For example, the recovered parameters in a two-dipole model for time-domain electromagnetics can be used to determine whether the object is magnetic (possibly UXO) or not and whether the object is plate-like (non-UXO) or rod-like (UXO).

The overall objective of this SERDP Exploratory Development (SEED) project was to determine how magnetic soils affect the recovered parameters from magnetic and EM inversions and, if significant, to explore possible techniques to mitigate their effects. Specific objectives included: (1) quantitatively evaluate the effects of the background susceptibility and thereby determine under what conditions the inversion algorithms can work (while ignoring these effects) and (2) determine how the data can be modified so that the current inversion algorithms will work in the presence of background susceptibility.