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DME: Distance Measuring Equipment

Distance Measuring Equipment (DME) is a ground-based navigation aid used by aircraft.

Signals transmitted between the aircraft and the DME ground beacon allow the aircraft to accurately determine its distance from the beacon. DME is used at an airport or en route and is one of the main navigation aids in air route systems.

DME equipment allows the distance between an aircraft and a ground station to be measured by timing the propagation delay of radio signals in the frequency band between 960 and 1215 megahertz (MHz). A line of sight is required between the aircraft and the ground station.

A common combination is a DME or



located with a VHF omnidirectional range (VOR) transmitter at a single ground station. When this occurs, the VOR and DME equipment frequencies are matched. This configuration allows an aircraft to determine its azimuth angle and distance from the station.

Low power DME transponders are also associated with some Instrument Landing System (ILS), ILS localizer, and Microwave Landing System (MLS) installations. In those situations, the DME transponder frequency/pulse spacing is also matched to the ILS, LOC, or MLS frequency.