Distance Measuring Equipment (DME) is defined as a combination of ground and airborne equipment that gives a continuous slant range distance-from-station readout by measuring time-lapse of a signal transmitted by the aircraft to the station and responded back. DMEs can also provide groundspeed and time-to-station readouts by differentiation. The DME will measure the distance in a straight line to the ground beacon (the slant range), not the distance from a point on the ground vertically below the aircraft (ground range). The difference is generally insignificant, except that when directly over a beacon when the distance shown will be height above the beacon.