radio navigation Radio navigation or radionavigation is the application of radio waves to geolocalization, determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of Radiodetermination-satellite servi ...

, a VOR/DME is a

radio beacon In navigation, a radio beacon or radiobeacon is a kind of beacon, a device that marks a fixed location and allows direction finding, direction-finding equipment to find relative Bearing (navigation), bearing. But instead of employing visible lig ...

that combines a

VHF omnidirectional range Very High Frequency Omnidirectional Range Station (VOR) is a type of short-range VHF radio navigation system for aircraft, enabling aircraft with a VOR receiver to determine the azimuth (also radial), referenced to magnetic north, between the a ...

(VOR) with a distance-measuring equipment (DME). The VOR allows the receiver to measure its bearing to or from the beacon, while the DME provides the slant distance between the receiver and the station. Together, the two measurements allow the receiver to compute a position fix. The VOR system was first introduced in the 1930s, but did not enter significant commercial use until the early 1950s. It became much more practical with the introduction of low-cost solid state receivers in the 1960s. DME was a modification of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

-era navigation systems like Gee-H, and began development in 1946. Like VOR, it only became practical with the introduction of solid state receivers during the 1960s. In 1948, the

United States Congress The United States Congress is the legislature, legislative branch of the federal government of the United States. It is a Bicameralism, bicameral legislature, including a Lower house, lower body, the United States House of Representatives, ...

directed civilian and military aviation to standardize on VOR/DME equipment. However, the military secretly developed a largely duplicate system called

TACAN A tactical air navigation system, commonly referred to by the acronym TACAN, is a navigation system initially designed for naval aircraft to acquire moving landing platforms (i.e., ships) and later expanded for use by other military aircraft. It p ...

. The system was revealed in 1952, but work continued into 1955, when the redundancy of effort caused controversy. The following year an agreement was reached, where civilian operators would adopt the

VORTAC Very High Frequency Omnidirectional Range Station (VOR) is a type of short-range VHF radio navigation system for aircraft, enabling aircraft with a VOR receiver to determine the azimuth (also radial), referenced to magnetic north, between the a ...

system.

During the mid-1960s,

ICAO The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sch ...

began the process of introducing a standardized radio navigation system for medium-area coverage on the order of a few hundred kilometres. This system would replace the older

Low-frequency radio range The low-frequency radio range, also known as the four-course radio range, LF/MF four-course radio range, A-N radio range, Adcock radio range, or commonly "the range", was the main Radio navigation, navigation system used by aircraft for instrumen ...

and similar systems used to navigate over national ranges. A number of proposals were submitted, including ones based solely on angle measurements like VOR, solely on distance measures like DME, combinations, or systems that output a location directly, like Decca Navigator and Loran-C. VOR/DME eventually won the standardization effort, due to a number of factors. One was that the direct measurement systems like Loran were generally much more expensive to implement (and would be into the 1980s) while Decca had problems with static interference from lightning strikes because of its low 70 to 129

kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base uni ...

frequency. The choice of VOR/DME as a hybrid was due largely to it being easier to measure and then plot on a map. With VOR/DME, measurement from a single station reveals an angle and range, which can be easily drawn on a chart. Using a system based on two angles, as an example, requires two measurements at different frequencies (or using two radios) and then the angles plotted from both on a single chart which may be difficult in a cramped cockpit. Eventually, the FAA began to integrate their VOR/DME facilities with stations based on the TACAN standard, and the stations are called VORTAC. Then, most aviation moved to GNSS and GPS satellite navigation, and only use these older systems as a backup.

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{{Reflist Radio navigation