Upward continuation for clutter suppression in EMI sensing of subsurface UXO

Clutter is the bane of electromagnetic induction (EMI) surveying for subsurface unexploded ordnance (UXO) under realistic circumstances. Relatively small near-surface metallic items can still produce significant signals simply because they are much closer to the sensor than the larger underlying target of interest. Based on measured, fully multi-static, scalar data at some typical elevation above the ground, one may infer a surface layer of equivalent sources that will produce that data. Without having to locate or characterize the actual targets, one can use these equivalent sources to predict complete vector field data that would be obtained at any elevation equal to or greater than that of the original data. Such computational upward continuation (UC) of signals successfully suppressed clutter in field data. This was even the case when the local clutter signal was significantly stronger than that of the broader underlying UXO response and was embedded directly within it. The success of the approach is directly tied to the fact that it relies on the governing physics.