Time-Domain EM (TDEM)
Time-domain EM is an active technique that induces small, transient eddy currents into the ground and then measures their rate of decay. The decay curve can provide information about the electrical properties of the earth materials or metal objects. TDEM is used for a variety of applications from mining to shallow metal detection.
At Geometrics, TDEM is synonymous with unexploded ordnance (UXO) detection and identification. Our UXO detection system is called the Metalmapper 2×2 system (previously the Metalmapper), and it is used exclusively for this purpose. Not only is it highly effective at locating UXO, it is demonstrably the best system for discriminating between shrapnel and intact ordnance. This drastically reduces cleanup costs by reducing the amount of digging.
See http://www.geometrics.com/geometrics-products/geometrics-electro-magnetic-products/metal-mapper/ for more information on the Metalmapper 2×2 system.
You may download the datasheet here.