Leading lights: Difference between revisions

{{refimprovemore citations needed|date=May 2012}}

[[Image:NantucketRangeLites.jpg|thumb|right|[[Nantucket Harbor Range Lights]]<ref name=cgll>{{cite uscgll|1|2009|135}}</ref> The dayboards[[dayboard]]s are type KRW, see below.]]

[[Image:Bremerhaven Unterfeuer 1.jpg|thumb|[[Bremerhaven lighthouseLighthouse|A pair of leading lights in Bremerhaven]], Germany, with the rear light in a proper lighthouse and the front light on a smaller tower. No standardised markings are used here.]]

'''Leading lights''', (also known as '''range lights''' in the [[United States]]), are a pair of light beacons, used in [[navigation]] <ref>{{cite web|url=http://www.ialathree.org/dictionary/index.php?title=Leading_Lights_%28G.B.%29 |title=Dictionary of the International Association of Lighthouse Authorities |publisher=[[International Association of Lighthouse Authorities]]}}</ref> to indicate a safe passage for vessels entering a shallow or dangerous channel; andthey may also be used for [[position fixing]]. At night, the lights are a form of [[Piloting#Piloting in channels and rivers|leading line]] that can be used for safe navigation. The beacons consist of two lights that are separated in distance and elevation, so that when they are aligned, with one above the other, they provide a bearing. Range lights are often illuminated day and night.

In some cases the two [[beacons]] are unlighted, in which case they are known as a '''range''' in the United States or a '''[[Navigational transit|transit]]''' in the UK. The beacons may be artificial or natural.

Two lights are positioned near one another. One, called the front light, is lower than the one behind, which is called the rear light. At night when viewed from a ship, the two lights only become aligned vertically when a vessel is positioned on the correct bearing.<ref>{{cite Ifbook the|last1=Bowditch vessel|first1=Nathaniel is|title=The onAmerican practical navigator : an incorrectepitome course,of thenavigation lights|date=2002 will|publisher=Paradise notCay alignPublications |location=Bethesda, Md. |isbn=9780939837540 |page=64 |edition=2004}}</ref>

Some major rivers, such as the [[Elbe|Elbe River]] in [[Germany]], have a series of leading lines. When it is necessary to make a turn, the navigator lines up the next pair of leading lights. This provides guidance from [[Hamburg]] to the sea, using successive pairs of leading lights.<ref>{{cite book |last1=Wendemuth |first1=Ludwig |title=The port of Hamburg, with plans, charts and numerous illustrations |date=1927 |publisher=Meissner & Christiansen |location=Hamburg |oclc=586327105 |page=204}}</ref>

Leading lights were used in EnglandGreat Britain as early as 1763 to mark the [[Port of Liverpool]].<ref>{{cite book|title=Lighthouses of Liverpool Bay |first=John |last=Robinson |first2=Diane |last2=Robinson |publisher=[[The History Press]] |year=2007 |isbn=978-0752442099}}</ref> The first set of range lights in the [[United States]] were privately established by subscription at [[Newburyport, Massachusetts|Newburyport Harbor]] in [[Massachusetts]] in 1788.<ref>{{cite book |last1=Roberts |first1=Bruce |last2=Shelton-Roberts |first2=Cheryl |last3=Jones &|first3=Ray Robert|title=American (1998)lighthouses : a comprehensive guide to exploring our national coastal treasures |date=2012 |publisher=Globe Pequot Press |location=Guilford, Conn. |isbn=9780762779604 |edition=3rd}}</ref>

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[[Category:NauticalMaritime termssignalling]]