180th meridian
The180th meridianorantimeridian[1]is themeridian180° both east and west of theprime meridianin ageographical coordinate system.Thelongitudeat this line can be given as eithereastorwest.
OnEarth,the prime and 180th meridians form agreat circlethat divides the planet into theWesternandEastern Hemispheres.The antimeridian passes mostly through the open waters of thePacific Oceanbut also runs across land inRussia,Fiji,andAntarctica.An important function of this meridian is its use as the basis for theInternational Date Line,which snakes around national borders to maintain date consistency within the territories of Russia, the United States, Kiribati, Fiji and New Zealand.
Starting at theNorth Poleof the Earth and heading south to theSouth Pole,the 180th meridian passes through:
The meridian also passes between (but not particularly close to):
- through theAleutian Islandchain of US territory
- theGilbert Islandsand thePhoenix IslandsofKiribati
- North Islandand theKermadec IslandsofNew Zealand
- theBounty Islandsand theChatham Islands,also of New Zealand
The only places where roads cross this meridian are in Fiji and Russia. Fiji has several such roads and some buildings very close to it. Russia has three roads in theChukotka Autonomous Okrug.
Software representation problems[edit]
Many geographic software libraries or data formats project the world to a rectangle; very often this rectangle is split exactly at the 180th meridian. This often makes it non-trivial to do simple tasks (like representing an area, or a line) over the 180th meridian. Some examples:
- TheGeoJSONspecification strongly suggests splitting geometries so that neither of their parts cross the antimeridian.[2]
- InOpenStreetMap,areas (like the boundary of Russia) are split at the 180th meridian.
- QGISmay present lines and polygons in a wrapped way if they cross the 180 meridian.
See also[edit]
Notes[edit]
- ^The wordantimeridiancan also mean the meridian opposite to any given meridian. E.g.20° westis the antimeridian of160° east.
- ^Butler, H.; Daly, M.; Doyle, A.; Gillies, S.; Hagen, S.; Schaub, T. (2016).RFC 7946 – The GeoJSON Format.sec. 3.1.9.doi:10.17487/RFC7946.RFC7946.
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