Editing History of radio (section)

==Radio navigation==
One of the first developments in the early 20th century was that aircraft used commercial AM radio stations for navigation, AM stations are still marked on U.S. aviation charts. [[Radio navigation]] played an important role during war time, especially in World War II. Before the discovery of the crystal oscillator, radio navigation had many limits.<ref>{{Cite web|title="Flying the Beam" {{!}} Time and Navigation|url=http://timeandnavigation.si.edu/navigating-air/challenges/overcoming-challenges/radio-navigation|access-date=2020-06-09|website=timeandnavigation.si.edu|language=en}}</ref> However, as radio technology expanding, navigation is easier to use, and it provides a better position. Although there are many advantages, the radio navigation systems often comes with complex equipment such as the radio compass receiver, compass indicator, or the radar plan position indicator. All of these require users to obtain certain knowledge.

In the 1960s [[VHF omnidirectional range|VOR]] systems became widespread. In the 1970s, [[LORAN]] became the premier radio navigation system. Soon, the US Navy experimented with [[satellite navigation]]. In 1987, the [[Global Positioning System]] (GPS) constellation of [[satellite]]s was launched; it was followed by other [[GNSS]] systems like [[Glonass]], [[BeiDou]] and [[Galileo (satellite navigation)|Galileo]].