Tracking roving miners or locating barricaded miners in a very large underground mining complex requires development of intrinsically safe hardware that can be deployed in an operating coal mine. For tracking operations, the transmitted signal will originate from the miner’s underground location. This technique consists of a cap lamp battery or self-contained self-rescuer with an intrinsically safe (IS) battery-powered tracking beacon operating in through-the-earth mode. A tracking beacon or cap lamp transmission antenna can be vertical magnetic dipole (VMD) or horizontal magnetic dipole (HMD) orientations. The through-the-earth electromagnetic (EM) wave travels directly upward through the overburden and is detected on the surface by the Delta Tracker.

The Delta Tracker is hand carried on the surface or flown on a helicopter to pinpoint the location of trapped miners by sensing the origin of the transmitted signal. The maximum response of the Delta Tracker can be correlated with global positioning system (GPS) information and mine maps to indicate the miner’s location within the mining complex as well as his depth below the surface. An important advantage of the Delta Tracker is that the surface radio frequency interference (RFI) noise is suppressed in the receiving antenna.  Without this feature, surface RFI noise would severely limit the depth of detection. During normal operating conditions, the Delta Tracker could be used to increase mine safety by locating abandoned oil and gas wells and old workings, as well as monitoring impoundment dams.