Empirically Derived Response Varibility for Munitions Items Using EM61 Towed Arrays

The depth at which UXO can be reliably detected using EM61 based arrays is not well understood. Most remedial actions use the empirically derived standard of 11 x diameter of a cylindrical munitions item as detection criteria. Unfortunately, the physics for forward modeling discrete, non-spherical conducting object responses to Time-Domain EM systems are very complex, especially for ganged arrays. There are no forward modeling algorithms available that can resolve this problem. Further, field experience and familiarity with the physics indicate this is a highly non-linear problem, where slight changes to the initial conditions can have a major impact on instrument response.