Discrimination of buried exploded ordnance by inversion of electromagnetic data requires accurate sensor positioning.
There are many contaminated areas were dense forest or significant topographic variation reduces accuracy or precludes
use of standard geo-location methods, such as satellite-based Global Positioning System (GPS) and laser tracking
systems (e.g., Robotic Total Station, RTS), as these rely on line of sight. We propose an alternative positioning system
that is based on a beacon principle. The system was developed to survey with the Man-Portable Vector (MPV) EMI
sensor. The magnetic moment of the MPV transmitter can be detected at a relatively large distance. The primary field is
measured from a portable base station comprised of two vector receivers rigidly attached to either ends of a 1.5 meter
horizontal boom. Control tests showed that relative location and orientation could be recovered with centimeter
positional and one degree angular accuracy within a 3-4-meter range and 60-degree aperture (relative to boom transverse
direction), which is more than sufficient to cover any UXO anomaly. This accuracy level satisfies commonly accepted
positional requirement for discrimination. The beacon positioning system can facilitate classification of munitions in any
man-trafficable area and was successfully deployed at a field demonstration.
The Man-Portable Vector (MPV) electromagnetic induction sensor has proved its worth and flexibility as a tool for identification
and discrimination of unexploded ordnance (UXO). TheMPV allows remediation work in treed and rough terrains
where other instruments cannot be deployed; it can work in survey mode and in a static mode for close interrogation of
anomalies. By measuring the three components of the secondary field at five different locations, the MPV provides diverse
time-domain data of high quality. TheMPV is currently being upgraded, streamlined, and enhanced to make it more practical
and serviceable. The new sensor, dubbedMPV-II, has a smaller head and lighter components for better portability. The
original laser positioning system has been replaced with one that uses the transmitter coil as a beacon. The receivers have
been placed in a configuration that permits experimental computation of field gradients. In this work, after introducing the
new sensor, we present the results of several identification/discrimination experiments using data provided by the MPV-II
and digested using a fast and accurate new implementation of the dipole model. The model performs a nonlinear search for
the location of a responding target, at each step carrying out a simultaneous linear least-squares inversion for the principal
polarizabilities at all time gates and for the orientation of the target. We find that the MPV-II can identify standard-issue
UXO, even in cases where there are two targets in its field of view, and can discriminate them from clutter.
Magnetic soils are a major source of false positives when searching for landmines or unexploded ordnance (UXO) with
electromagnetic induction sensors. The viscosity effects of magnetic soil can be accurately modeled by assuming a
ferrite relaxation with a log-uniform distribution of time constants. The frequency domain response of ferrite soils has a
characteristic negative log-linear in-phase and constant quadrature component. After testing and validating that
assumption, we process frequency domain electromagnetic data collected over UXO buried in a viscous remanent
magnetic host. The first step is to estimate a spatially smooth background magnetic susceptibility model from the
sensor. The response of the magnetically susceptibility background is then subtracted from the sensor data. The
background removed data are then inverted to obtain estimates of the dipole polarization tensor. This technique is
demonstrated for the discrimination of UXO with hand-held Geophex GEM3 data collected at a contaminated site near
Denver, Colorado.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.