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Automated Anomaly Picking From Broadband Electromagnetic Data In Uxo SurveyNormal access

Authors: Haoping Huang and I.J. Won
Event name: 16th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: Unexploded Ordnance
Publication date: 06 April 2003
Organisations: EEGS
Language: English
Info: Extended abstract, PDF ( 295.65Kb )

Summary:
We present automated anomaly-picking methods for detecting unexploded ordnance from
broadband electromagnetic data. Using data consisting of in-phase and quadrature responses at multiple
(typically 10) frequencies, a “detector function” attempts to detect all metal objects but to suppress false
alarms caused by geology, variations in sensor height, and sensor motions in the earth’s magnetic field.
Promising detector functions considered here are (1) the sum of all quadrature responses, Q-sum,
(2) the sum of all differences among the in-phase or quadrature components, I- or Q-spread, (3) the sum
of the I- and Q-spreads, T-spread, (4) the weighted total apparent conductivity, TAC, from all
frequencies, and (5) the apparent magnetic susceptibility, AMS, derived from the lowest frequency of a
survey. These detector functions favor metallic objects and are relatively insensitive to geologic
variations and motion-induced noise that are common with a handheld sensor or a cart-mounted sensor
in rough terrain. We discuss the properties of these detector functions, apply them to field data from two
sites, and compare the results with limited ground truths.

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