Editing Navigation (section)

====Radio navigation====
{{main|Radio navigation|Radio direction finder}}
[[File:Accuracy of Navigation Systems.svg|thumb|upright=1.2]]
A radio direction finder or RDF is a device for finding the direction to a [[radio]] source. Due to radio's ability to travel very long distances "over the horizon", it makes a particularly good navigation system for ships and aircraft that might be flying at a distance from land. RDFs works by rotating a directional [[Antenna (electronics)|antenna]] and listening for the direction in which the signal from a known station comes through most strongly. This sort of system was widely used in the 1930s and 1940s. RDF antennas are easy to spot on [[Germany|German]] [[World War II]] aircraft, as loops under the rear section of the fuselage, whereas most [[United States|US]] aircraft enclosed the antenna in a small teardrop-shaped fairing.

In navigational applications, RDF signals are provided in the form of ''radio beacons'', the radio version of a [[lighthouse]]. The signal is typically a simple [[Amplitude modulation|AM]] broadcast of a [[morse code]] series of letters, which the RDF can tune in to see if the beacon is "on the air". Most modern detectors can also tune in any commercial radio stations, which is particularly useful due to their high power and location near major cities.

[[Decca Navigator System|Decca]], [[OMEGA Navigation System|OMEGA]], and [[LORAN-C]] are three similar hyperbolic navigation systems. Decca was a [[hyperbola|hyperbolic]] [[low frequency]] [[radio navigation]] system (also known as [[multilateration]]) that was first deployed during [[World War II]] when the Allied forces needed a system which could be used to achieve accurate landings. As was the case with [[Loran C]], its primary use was for ship navigation in coastal waters. Fishing vessels were major post-war users, but it was also used on aircraft, including a very early (1949) application of moving-map displays. The system was deployed in the North Sea and was used by helicopters operating to [[oil platform]]s.

The OMEGA Navigation System was the first truly global [[radio navigation]] system for aircraft, operated by the [[United States]] in cooperation with six partner nations. OMEGA was developed by the United States Navy for military aviation users. It was approved for development in 1968 and promised a true worldwide oceanic coverage capability with only eight transmitters and the ability to achieve a four-mile (6&nbsp;km) accuracy when fixing a position. Initially, the system was to be used for navigating nuclear bombers across the North Pole to Russia. Later, it was found useful for submarines.<ref>{{Cite web |last=Proc |first=Jerry |title=Omega |url=http://www.jproc.ca/hyperbolic/omega.html |access-date=2024-11-22 |website=www.jproc.ca}}</ref> Due to the success of the [[Global Positioning System]] the use of Omega declined during the 1990s, to a point where the cost of operating Omega could no longer be justified. Omega was terminated on September 30, 1997, and all stations ceased operation.

LORAN is a terrestrial [[radio-navigation|navigation]] system using [[low frequency]] radio transmitters that use the time interval between radio signals received from three or more stations to determine the position of a ship or aircraft. The current version of LORAN in common use is LORAN-C, which operates in the [[low frequency]] portion of the EM spectrum from 90 to 110 [[Hertz|kHz]]. Many nations are users of the system, including the [[United States]], [[Japan]], and several European countries. Russia uses a nearly exact system in the same frequency range, called [[CHAYKA]]. LORAN use is in steep decline, with [[Global Positioning System|GPS]] being the primary replacement. However, there are attempts to enhance and re-popularize LORAN. LORAN signals are less susceptible to interference and can penetrate better into foliage and buildings than GPS signals.