Editing Radio navigation (section)

==Satellite navigation==
[[File:Cessna T182T Cockpit - Garmin G1000.jpg|thumb|right|200px|Cessna 182 with GPS-based "glass cockpit" avionics]]
{{Main|Satellite navigation}}
Since the 1960s, navigation has increasingly moved to [[satellite navigation system]]s. These are essentially hyperbolic<ref name="Abel1">"Existence and uniqueness of GPS solutions", J.S. Abel and J.W. Chaffee, ''IEEE Transactions on Aerospace and Electronic Systems'', vol. 26, no. 6, pp. 748–53, Sept. 1991.</ref><ref name="Fang2">"Comments on "Existence and uniqueness of GPS solutions" by J.S. Abel and J.W. Chaffee", B.T. Fang, ''IEEE Transactions on Aerospace and Electronic Systems'', vol. 28, no. 4, Oct. 1992.</ref> systems whose transmitters are in orbits. That the satellites move with respect to the receiver requires that the calculation of the positions of the satellites must be taken into account, which can only be handled effectively with a computer.{{fact|date=July 2022}}

Satellite navigation systems send several signals that are used to decode the satellite's position, distance between the user satellite, and the user's precise time. One signal encodes the satellite's ''ephemeris'' data, which is used to accurately calculate the satellite's location at any time. Space weather and other effects causes the orbit to change over time so the ephemeris has to be updated periodically. Other signals send out the time as measured by the satellite's onboard [[atomic clock]]. By measuring signal times of arrival (TOAs) from at least four satellites, the user's receiver can re-build an accurate clock signal of its own and allows hyperbolic navigation to be carried out.{{fact|date=July 2022}}

Satellite navigation systems offer better accuracy than any land-based system, are available at almost all locations on the Earth, can be implemented (receiver-side) at modest cost and complexity, with modern electronics, and require only a few dozen satellites to provide worldwide coverage{{citation needed|date=January 2019}}. As a result of these advantages, satellite navigation has led to almost all previous systems falling from use{{citation needed|date=January 2019}}. LORAN, Omega, Decca, Consol and many other systems disappeared during the 1990s and 2000s{{citation needed|date=January 2019}}. The only other systems still in use are aviation aids, which are also being turned off{{citation needed|date=January 2019}} for long-range navigation while new [[differential GPS]] systems are being deployed to provide the local accuracy needed for blind landings.{{fact|date=July 2022}}