Testing of a locating discriminating metal detector for landmine detection

Conventional metal detectors are established and trusted tools for landmine detection, but their inability to precisely locate a target and discriminate mines from clutter leads to a high false alarm rate and slow rate of progress. This paper reports on developments to the Marmot advanced metal detector, which uses an array of coils to precisely locate a metal target in three dimensions and identify it. Recent developments allow the detector to calculate the magnetic polarizability tensor of a metal object. The magnetic polarizability tensor is unique to a particular target, and is a property of the metal's shape, size, conductivity, permeability and orientation. The eigenvalues of the magnetic polarizability tensor are compared to a library of values in the detector's software, representing common types of mine and clutter. In this way, Marmot can often quickly identify a detected object as a type of mine or a piece of clutter. This identification is independent of the target's orientation and, within limits, its position relative to the search head, thus providing the potential for a target recognition facility. This paper presents the results of tests to determine Marmot's ability to detect, precisely locate and identify common landmines. Tests have been conducted in air and in several types of soil. The instrument is a first step in developing the concept for landmine clearance. Issues for further investigation have been identified, including use of the instrument for identifying high metal content landmines, application of the soil rejection function and signal to noise issues.