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Improving Uxo Characterization Accuracy By Accounting For Sensor Position And Orientation EffectsNormal access

Authors: Robert Mehl, Jack Foley and Lanbo Liu
Event name: 17th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: UXO Detection
Publication date: 22 February 2004
Organisations: EEGS
Language: English
Info: Extended abstract, PDF ( 935.57Kb )

Detection and characterization of small subsurface targets such as unexploded ordnance
(UXO) derived from analysis of electromagnetic induction (EMI) data fundamentally relies on
accurate spatial registration of all collected data. The uncertainties in position and orientation of
the EM source and receiver coils are the largest source of errors that affect the fidelity of the
data, which, in turn, determines the accuracy and reliability of target characterization. This paper
addresses the challenges of how to precisely obtain the three-dimensional sensor positioning and
orientation and quantitatively discuss their influences and compensation to the observed EMI
data. Three topics are explored: 1) the inadequacy of conventional Global Positioning System
(GPS) technology for 3D positional data and improvements available from robotic total station
(RTS) technology; 2) the systematic assessment of EMI target signature effects caused by
various conditions of sensor mis-location and orientation deviations; and 3) the collection of
supplemental 3-axis gyro orientation measurements (yaw, pitch and roll) and 3-axis acceleration
measurements to facilitate geophysical analysis techniques that account for varying sensor
orientation during data collection. Over some targets, recent controlled tests document EMI
peak amplitude responses reduced by up to 30% when the sensor was tilted as little as 5 degrees.
The incorporation of orientation information into EMI inversion modeling algorithms is
necessary to use these parameter-based discrimination methods in order to classify targets and
reduce false alarms.

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