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REPORT DATE
MAY 20102First, we developed a principal component analysis algorithm tailored to unexploded ordnance applications. Decay characteristics of TEM data preclude the standard Karhunen-Loéve transform; we have addressed these issues with algorithm modifications and incorporated these into the workflow.Secondly, we identified the optimum choice of principal components for the attenuation of both random noise and correlated noise, leaving the signal due to UXO intact. We show that the processed data is optimally prepared for automatic anomaly picking routines with a highly reduced number of false anomalies. We demonstrate this on both synthetic examples of UXO surveys, as well as on TEM data from Kaho'olawe, Hawaii, USA.iii Finally, we have identified a critical issue with inversion of processed data that results in extremely inaccurate recovered models without the incorporation of the PCA process into the forward model. We developed an inversion algorithm which takes the processing steps into account during construction of the inverse kernels.This leads to more accurate recovered models of inverted anomalies.iv The goal is to increase the signal-to-noise ratio of the TEM data as well as to generate an estimate of data noise characteristics (statistical distribution and associated parameters) for use in subsequent inversion-based discrimination.One of the most effective geophysical techniques for UXO application is the transient electromagnetic method. Using a loop as a source, a time-varying magnetic field is generated at the surface which in turn induces electrical currents in the ground, and more importantly in buried metallic objects. Once induced, these currents dissipate over time due to ohmic losses, leading to a measured transient decay in magnetic field flux density at the surface by geophysical sensors. The currents induced in the surrounding medium and in the buried metallic ob...