Discrimination and Identification of UXO by Geophysical Inversion. Phase II: Inversion of Total-Field Magnetics

Abstract : A dipole inversion method was developed and successfully applied to the discrimination and identification of unexploded ordnance using total-field magnetometry. A black-white classification of anomalies as ordnance/non-ordnance is not possible using magnetics; rather the items can be ranked according to the likelihood they are UXO. The discrimination method had the potential to reduce the number of excavations at an impact site in Montana (Guthrie Road) by half, yet still yielded all the ordnance. The method requires complete or at least partial shock demagnetization of ordnance, otherwise it is not possible to reliably rank the anomalies. Error analysis indicates that recovered dipole moments are relatively well constrained. However, identification of the anomaly source is difficult using the recovered dipole moment due to non-uniqueness. By recognizing that there are a finite number of ordnance types, correct identification could be achieved in about 55% of cases. Extension of the inversion method to recover either quadrupole of octupole moments did not improve our ability to discriminate or identify.