The discrimination task inevitably proceeds from some data that reflects responses in a particular survey environment in order to infer quantities of interest on which discrimination calculations and judgments may be based. These quantities almost always include intrinsic electromagnetic parameters, through which TOIs may be classified, and extrinsic parameters, such as object location and disposition. Extrinsic parameters are vital and their determination cannot usually be avoided entirely. They are required first by the mathematical operators used to solve for the intrinsic parameters. Additionally, UXO positional information is needed for actual remediation activities. The computation of extrinsics may also pertain to underlying or surrounding issues, such as how many objects are contributing and what response may be coming from the geophysical environment. The broad expanse of geophysical inversion theory and practice is well beyond the scope and intent of this book; space and succinctness also do not allow inclusion of the particulars of all that has been attempted specifically in UXO discrimination applications. For accessible introductions to general geophysical inversion, see Scales et al.1 and the overviews in UBC-GIF2 and Oldenburg and Li.3 This chapter is designed to illuminate the nature of the problem and to describe the primary concerns, challenges, and pitfalls most closely connected to UXO discrimination. It further provides constructive strategies that are most likely to be useful for confronting common problems. Related material and some treatment of supporting techniques appear in Chapters 7 and 8.
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