Fast approximate EM induction modeling of metallic and UXO targets using a permeable prism

Asten, Michael; Duncan, Andrew

doi:10.1016/j.jappgeo.2006.05.010

Cited by 11 publications

(5 citation statements)

References 13 publications

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“…At lower frequencies, their sensitivity is reduced. Asten and Duncan (2007) list a number of potential benefits of B-field measurements including a higher sensitivity to large deep items compared to small shallow items. Our objective was not to rigorously determine the tradeoffs between B and dB/dt measurements during the on-time, but to provide example responses for both modalities.…”

Section: B and Db/dt Measurement Methodsmentioning

confidence: 99%

Exploiting EMI Signals During Active Transmission

Schultz¹,

Miller²,

Pasion³

2010

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Section: B and Db/dt Measurement Methodsmentioning

confidence: 99%

Exploiting EMI Signals During Active Transmission

Schultz¹,

Miller²,

Pasion³

2010

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“…• enhances UXO signal relative to scrap • improves sensitivity of the EM system to deeper UXO targets below surface scrap Modeling example Asten and Duncan (2007b) introduced an approximation model for EMI response of conductive permeable objects, using a prism approximation. The approximation algorithm is a development of the multiple current loop algorithm described by Lamontagne et al (1988Lamontagne et al ( , 2004.…”

Section: Wb138mentioning

confidence: 99%

The quantitative advantages of using B-field sensors in time-domain EM measurement for mineral exploration and unexploded ordnance search

Asten

Duncan

2012

GEOPHYSICS

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The use of simple models for decay of conductive targets under conductive overburden and for the decay of magnetically permeable conductive steel objects allows quantitative consideration of the advantages of the use of magnetic-field detectors in time-domain electromagnetic (TEM) measurements, or more generally, the advantage of step response over impulse response TEM systems. We identified eight advantages of the step response versus impulse-response systems. The first two advantages relate to the inductive limit (early time) decay behavior, in which a target response amplitude is largely dependent on geometrical rather than conductivity parameters. Five further advantages occur when measuring response of a target in a conductive host or under conductive overburden; the maximum target-tooverburden response occurs 25%-30% earlier in time, the earliest target detection time occurs a factor 2-4 earlier, and the amplitude advantage of target-to-overburden response is a factor in the range of 1-10 for the step versus impulse-response systems, respectively. These advantages agree quantitatively with field observations on a chalcopyrite orebody under conductive cover. We used a model response for a conductive permeable sphere to derive mathematically consistent approximations for the power-law and exponential decay behaviors for step and impulse responses of metal objects, from which the onset of late-time exponential decay of EM responses of unexploded ordnance occurs about a factor of two earlier in time for the step response. This earlier-time transition together with the higher signal-to-noise ratio available from the step-response measurement makes measurement of the fundamental timeconstant of unexploded ordnance (UXO) possible for medium and large UXO where the time constant is in the range of tens of milliseconds. This time-constant thus becomes accessible as an additional parameter for UXO characterization and discrimination.

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“…Asten and Duncan (2007) have developed a fast approximate forward algorithm for determining the electromagnetic response of a permeable, highly conductive target. The surface of the body is decomposed into a number of rectangular facets, each of which is modeled as a set of concentric wire loops that is inductively coupled to the transmitter and to the other facets.…”

Section: Target Recognitionmentioning

confidence: 99%

Theoretical Developments in Electromagnetic Induction Geophysics with Selected Applications in the Near Surface

Everett

2011

Surv Geophys

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Near-surface applied electromagnetic geophysics is experiencing an explosive period of growth with many innovative techniques and applications presently emergent and others certain to be forthcoming. An attempt is made here to bring together and describe some of the most notable advances. This is a difficult task since papers describing electromagnetic induction methods are widely dispersed throughout the scientific literature. The traditional topics discussed herein include modeling, inversion, heterogeneity, anisotropy, target recognition, logging, and airborne electromagnetics (EM). Several new or emerging techniques are introduced including landmine detection, biogeophysics, interferometry, shallow-water electromagnetics, radiomagnetotellurics, and airborne unexploded ordnance (UXO) discrimination. Representative case histories that illustrate the range of exciting new geoscience that has been enabled by the developing techniques are presented from important application areas such as hydrogeology, contamination, UXO and landmines, soils and agriculture, archeology, and hazards and climate.

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Fast approximate EM induction modeling of metallic and UXO targets using a permeable prism

Cited by 11 publications

References 13 publications

Exploiting EMI Signals During Active Transmission

Exploiting EMI Signals During Active Transmission

The quantitative advantages of using B-field sensors in time-domain EM measurement for mineral exploration and unexploded ordnance search

Theoretical Developments in Electromagnetic Induction Geophysics with Selected Applications in the Near Surface

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