Intra-Inversion Filtering for Use of Magnetic Fields to Locate and Characterize Magnetic Dipoles for Unexploded Ordnance (UXO) Cleanup
RENE GEOPHYSICS BLOOMINGTON IN
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This SEED project was successful in developing high-pass intra-inversion filtering IIF as a new method to improve inversion of magnetic anomalies in unexploded ordnance UXO magnetic field surveys. IIF allows accurate inversion of UXO magnetic anomalies in the presence of lowfrequency background fields and overlapping anomalies of neighboring UXO and clutter. The need for this has been well recognized by SERDP and the UXO community ESTCP-ITRCSERDP, 2006. As part of this project, an unexpected invention of the edge-adaptive gapped gradient-nulling EAGGN filter was made. This new filter automatically accommodates data gaps, survey edges and corners, flag-node data, in which only the nodes of a grid that are nearest to magnetometer stations are used, single-swaths of towed-array data, and restrictions of the filter input to any desired data window. Other related high-pass IIF were developed and applied to all-node inversions using data interpolated to all nodes of a regular grid. High-pass IIF will become an important new tool for magnetic field inversion. The purpose of full point-dipole magnetic field inversion is to extract the location, depth, magnitude and orientation of magnetic dipoles associated with UXO or clutter. Accurate estimates of horizontal location and depth facilitate subsequent excavation, if required. Accurate estimates of depth, magnetic dipole strength, and magnetic orientation are essential to the following processes of geophysical interpretation that seek to discriminate between UXO and clutter and to characterize the likely type of any UXO. Magnetic and electromagnetic induction EMI are the two principal means of UXO geophysical surveys. These two methods complement each other and together are especially successful when used together. The purpose of UXO geophysical surveys is to detect UXO, to discriminate between UXO and clutter, and to characterize the likely type of UXO prior to excavation for remediation of UXO-contaminated lands.
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