DME

Distance Measurement Equipment (DME) is used to give the pilot the information of its distance away from the VOR station, thus with a bearing and distance from a particular known VOR station a pilot can fix his exact position. Such systems are referred to as VOR/DME. DME is also part of a military navigation system widely used in the US, the TACAN (TACtical Air Navigation). A ground station combining VOR and TACAN is known as VOR-TAC. Needless to mention, the frequencies for the VOR and DME or VOR and TACAN are paired by international standards, thus once a pilot tunes onto a particular VOR frequency the airborne equipment will automatically tunes on the co-located DME or Tacan