Editing Rantum Loran-C transmitter (section)

==Loran-C==
{{Main|LORAN}}
Loran-C is a system of [[hyperbolic navigation|hyperbolic]] [[radio navigation]] which developed from the earlier [[LORAN]] system. It uses low frequency signals from beacons to allow the receiver to determine their position. Conventional navigation involves measuring the distance from two known locations, radio navigation works in a similar way but using [[radio direction finding]].<ref>{{Cite book| author=Appleyard, S.F. |author2=Linford, R.S. |author3=Yarwood, P.J.| title=Marine Electronic Navigation |year=1988 | publisher=Routledge & Kegan Paul| pages=77–83 | isbn=0-7102-1271-2|edition=2nd }}</ref>

Radio navigation systems use a chain of three or four transmitters which are synchronised. Each chain has a primary station and the others are called secondaries. Each chain has a group repetition interval (GRI) which, multiplied by ten, is the time difference between pulses. The GRI identifies which chain a vessel is receiving. <ref>{{citeweb|author=E. Gatterer|url=https://archive.org/details/TheDevelopmentOfLoranCNavigationAndTiming |title=The Development of Loran-C Navigation and Timing|publisher= National Bureau of Standards|date=October 1972}}</ref>

Loran-C was replaced by civilian [[Satellite navigation]] systems starting in the 1990s. The first services to close were in the United States and Canada in 2010.<ref>{{Cite web | title = USCG LORAN Program Manager release, Nov. 2009 | date = 31 May 2007 | url = http://www.uscg.mil/ANNOUNCEMENTS/alcoast/675-09_alcoast.txt | access-date = 28 November 2009}}</ref><ref>{{Cite web|url=https://www.navcen.uscg.gov/?pageName=loranMain|title=LORAN-C General Information|website=www.navcen.uscg.gov}}</ref> In 2014 France and Norway announced they were closing their transmitters, leaving the remaining stations in England and Germany unable to operate.<ref>{{cite web|url=https://www.trinityhouse.co.uk/notice-to-mariners/27-15-enhanced-loran-discontinued|title=27-15 Enhanced Loran discontinued|publisher=[[Trinity House]]|series=[[Notice to Mariners]]|date=1 December 2015}}</ref><ref>{{cite web |title=Loran Off Air In Most of Europe - Move to Commercial Possible |url=https://rntfnd.org/2016/01/04/loran-off-air-in-most-of-europe-move-to-commercial-possible/ |website=RNTF |access-date=7 April 2025 |date=4 January 2016}}</ref> The stations in Norway closed on 31 December 2015.<ref name="kartverket">{{cite web |title=Etterretninger for sjøfarende |url=https://kartverket.no/efs-documents/editions/2015/efs01-2015.pdf |website=Kartverket |access-date=7 April 2025 |page=26 |language=Norwegian|date=2015}}</ref>