DME

A navigation aid that measures the slant-range distance between the aircraft and a ground station, in nautical miles. The aircraft sends pulses, the station replies, and the time taken gives the distance; most receivers also show ground speed and time to the station.

DME is usually co-located with a VOR or ILS, so a VOR/DME gives you a radial and a distance: a full position fix. Directly above the station at height, the slant range is more than the ground distance.