Dr. Mark N. Keene Profile

Dr. Mark N. Keene

at QinetiQ Ltd

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Proceedings Article | 21 September 2004 Paper

A novel locating and discriminating metal detector

Mark Keene, Matthew Wooliscroft, Richard Humphreys, Darren Riley, Robert Deas

Proceedings Volume 5415, (2004) https://doi.org/10.1117/12.549692

KEYWORDS: Sensors, Metals, Land mines, Target detection, Mining, Head, Magnetism, Transmitters, Receivers, Detection and tracking algorithms

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We present the first report of a new experimental metal detector that is able to locate an underground metal object in three dimensions with an accuracy of millimeters and measure a signature to provide discrimination against frag (chaff). The ability to pinpoint the metal means that the physical excavation of the target can be conducted more quickly and safely. This detector consists of a single transmitter coil, an array of 40 receiver coils and a computer to control soil rejection and data inversion. An inversion algorithm returns the 3D location of a target with respect to the sensor head and the signature of the metal object that is largely independent of the geometry of the measurement. Tests were conducted in air, in sand and in soil using various surrogate mines and cartridge cases. Location accuracy was generally found to be very good. Several samples of a range of mine surrogates had their signatures recorded, and all samples of each type were found to have a signature falling in a very narrow band. Most of these bands are well separated, leading us to conclude that there is considerable potential for discrimination against frag. During a blind test 80% of the mines were correctly identified. We conclude that this experimental detector can accurately locate metal objects in three dimensions and provide useful information for discriminating frag from mines. This paper reports on the technology within the new detector and the early results of the performance tests conducted against surrogate mines in test lanes.

Proceedings Article | 11 September 2003 Paper

Synthetic magnetic soils for landmine detector testing

Mark Keene, Thomas Horton, Michael Styles, Ellie Steadman, Simon Kemp, Emily Hodgkinson

Proceedings Volume 5089, (2003) https://doi.org/10.1117/12.488498

KEYWORDS: Sensors, Magnetism, Soil science, Metals, Signal detection, Magnetic sensors, Particles, Minerals, Land mines, Mining

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This study aims to move towards a reliable method for synthesizing artificial soils that emulate the effect of real soils on pulse-induction metal detectors. The signals resulting from some mineralized soils can greatly impair the effectiveness of mine detectors. We analysed a sample of one such soil from Cambodia, using resistivity measurement, X-ray diffraction, magnetic susceptibility measurement and electron microscopy. The physical origin of the soil signal was found to be high proportions of small grained magnetite. By mixing a U.K. topsoil with finely crushed magnetite, a synthetic soil with similar magnetic susceptibility to the real Cambodian soil was created. Other problematic soils from around the world were also synthesized. Comparative tests with a pulse induction metal detector showed decay characteristics for the artificial soils to be within 13% of those for the real soil. We achieved close susceptibility matching between artificial and real soils, either for a 2kHz measurement or a pulse-induction measurement. In our experiments it was not possible to match with both measurements at once. We propose that this discrepancy is due to differences in the average properties of magnetic grains between those in real soil and the magnetite concentrate used for the synthesis tests.

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