Cooperative Inversion of Time Domain Electromagnetic and Magnetometer Data for The Discrimination of Unexploded Ordnance

2008 ◽  
Vol 13 (3) ◽  
pp. 193-210 ◽  
Author(s):  
L. R. Pasion ◽  
S. D. Billings ◽  
K. A. Kingdon ◽  
D. W. Oldenburg ◽  
N. Lhomme ◽  
...  
Keyword(s):  
Time Domain ◽  
Unexploded Ordnance ◽  
Magnetometer Data ◽  
Time Domain Electromagnetic ◽  
Cooperative Inversion

Field tests of an experimental helicopter time‐domain electromagnetic system for unexploded ordnance detection

Geophysics ◽  
2004 ◽  
Vol 69 (3) ◽  
pp. 664-673 ◽  
Author(s):  
Les P. Beard ◽  
William E. Doll ◽  
J. Scott Holladay ◽  
T. Jeffrey Gamey ◽  
James L.C. Lee ◽  
...  
Keyword(s):  
Time Domain ◽  
Eddy Currents ◽  
Field Tests ◽  
Field Trials ◽  
Unexploded Ordnance ◽  
Signal Attenuation ◽  
Signal To Noise ◽  
Electromagnetic System ◽  
Time Domain Electromagnetic ◽  
Unexploded Ordnance Detection

Field trials of a low‐flying time‐domain helicopter electromagnetic system designed for detection of unexploded ordnance have yielded positive and encouraging results. The system is able to detect ordnance as small as 60‐mm rounds at 1‐m sensor height. We examined several transmitter and receiver configurations. Small loop receivers gave superior signal‐to‐noise ratios in comparison to larger receiver loops at low heights. Base frequencies of 90 Hz and 270 Hz were less affected than other base frequencies by noise produced by proximity to the helicopter and by vibration of the support structure. For small ordnance, a two‐lobed, antisymmetric transmitter loop geometry produced a modest signal‐to‐noise enhancement compared with a large single rectangular loop, presumably because the antisymmetric transmitter produces smaller eddy currents in the helicopter body, thereby reducing this source of noise. In most cases, differencing of vertically offset receivers did not substantially improve signal‐to‐noise ratios at very low sensor altitudes. Signal attenuation from transmitter to target and from target to receiver causes signals from smaller ordnance to quickly become indistinguishable from geological background variations, so that above a sensor height of about 3 m only large ordnance items (e.g., bombs and large caliber artillery rounds) were consistently detected.

Joint diagonalization applied to the detection and discrimination of unexploded ordnance

Geophysics ◽  
2012 ◽  
Vol 77 (4) ◽  
pp. WB149-WB160 ◽  
Author(s):  
Fridon Shubitidze ◽  
Juan Pablo Fernández ◽  
Irma Shamatava ◽  
Benjamin E. Barrowes ◽  
Kevin O’Neill
Keyword(s):  
Time Domain ◽  
Detection System ◽  
Naval Research ◽  
Unexploded Ordnance ◽  
Mathematical Basis ◽  
Joint Diagonalization ◽  
Data Inversion ◽  
Standard Procedures ◽  
Time Domain Electromagnetic ◽  
Single Matrix

Efforts to discriminate buried unexploded ordnance from harmless surrounding clutter are often hampered by the uncertainty in the number of buried targets that produce a given detected signal. We present a technique that helps determine that number with no need for data inversion. The procedure is based on the joint diagonalization of a set of multistatic response (MSR) matrices measured at different time gates by a time-domain electromagnetic induction sensor. In particular, we consider the Naval Research Laboratory’s Time-Domain Electromagnetic Multisensor Towed Array Detection System (TEMTADS), which consists of a [Formula: see text] square grid of concentric transmitter/receiver pairs. The diagonalization process itself generalizes one of the standard procedures for extracting the eigenvalues of a single matrix; in terms of execution time, it is comparable to diagonalizing the matrices one by one. We present the method, discuss and illustrate its mathematical basis and physical meaning, and apply it to several actual measurements carried out with TEMTADS at a test stand and in the field at the former Camp Butner in North Carolina. We find that each target in a measurement is associated with a set of nonzero time-dependent MSR eigenvalues (usually three), which enables estimation of the number of targets interrogated. These eigenvalues have a characteristic shape as a function of time that does not change with the location and orientation of the target relative to the sensor. We justify analytically and empirically that symmetric targets have pairs of eigenvalues with constant ratios between them.

Application of a library based method to time domain electromagnetic data for the identification of unexploded ordnance

2007 ◽  
Vol 61 (3-4) ◽  
pp. 279-291 ◽  
Author(s):  
Leonard R. Pasion ◽  
Stephen D. Billings ◽  
Douglas W. Oldenburg ◽  
Sean E. Walker
Keyword(s):  
Time Domain ◽  
Unexploded Ordnance ◽  
Electromagnetic Data ◽  
Time Domain Electromagnetic
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