HR: 10:45h
AN: NS12A-02 INVITED     [Abstracts]
TI: A Multi-Object Inversion Approach for Efficient Magnetic Discrimination of Unexploded Ordnance
AU: * Billings, S
EM: stephen.billings@skyresearch.com
AF: Sky Research Inc, Suite 311 2386 East Mall, Vancouver, BC V6T1Z3 Canada
AU: Oldenburg, D
EM: doug@eos.ubc.ca
AF: The University of British Columbia - Geophysical Inversion Facility, 6339 Stores Road, Vancouver, BC V6T1Z4 Canada
AU: Pasion, L
EM: lpasion@eos.ubc.ca
AF: The University of British Columbia - Geophysical Inversion Facility, 6339 Stores Road, Vancouver, BC V6T1Z4 Canada
AB: Magnetometery is one of the primary methods used for detecting buried unexploded ordnances, either in a standalone mode, or in conjunction with electromagnetic induction. UXO's and other metallic debris generally appear as dipolar anomalies overprinting larger scale magnetic features due to near-surface magnetite variations and the regional geology. Non-linear high-pass filters are usually used to remove the larger scale effects and the remaining dipolar anomalies are inverted one at a time by an efficient bound-constrained optimization algorithm. This process works well when the individual anomalies are well separated and the geological variations are at larger scales than the UXO anomalies. When these conditions don't apply the inversion results are unreliable and the process of inverting each anomaly becomes time-consuming and unwieldy. We have developed an efficient multi-object inversion routine that allows simultaneous inversion of an arbitrary number of dipolar anomalies. Providing a good initial guess as to the number, location, magnitude and orientation of each dipole is critical to the success of the algorithm. We have found that an Automated Wavelet Detection algorithm we developed in a previous paper is ideal for this purpose. The multi-object inversion approach is very effective in most situations, but, like the original single-object approach, has trouble dealing with datasets with significant geological contamination. In an effort to overcome this problem we outline a framework for coupling our multi-object inversion scheme with an equivalent layer technique that attempts to model the background geology.
DE: 0903 Computational methods, potential fields
DE: 0910 Data processing
DE: 0925 Magnetic and electrical methods
DE: 1517 Magnetic anomaly modeling
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly