180th meridian

Antimeridian

The International Date Line zigzags around the 180th Meridian.

The 180th meridian or antimeridian^[1] is the meridian which is 180° east or west of the Prime Meridian with which it forms a great circle which divides the earth into the Western Hemisphere and Eastern Hemisphere. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it for the most part passes through the open waters of the Pacific Ocean. However, the meridian passes through Russia and Fiji as well as Antarctica.

Starting at the North Pole and heading south to the South Pole, the 180th meridian passes through:

Co-ordinates (approximate)	Country, territory or sea	Notes
90°0′N 180°0′E / 90.000°N 180.000°E	Arctic Ocean
71°32′N 180°0′E / 71.533°N 180.000°E	Russia	Chukotka Autonomous Okrug — Wrangel Island
70°58′N 180°0′E / 70.967°N 180.000°E	Chukchi Sea
68°59′N 180°0′E / 68.983°N 180.000°E	Russia	Chukotka Autonomous Okrug
65°02′N 180°0′E / 65.033°N 180.000°E	Bering Sea
52°0′N 180°0′E / 52.000°N 180.000°E	Amchitka Pass	Passing just east of Semisopochnoi Island, Alaska,  United States (at 51°57′N 179°47′E / 51.950°N 179.783°E)
51°0′N 180°0′E / 51.000°N 180.000°E	Pacific Ocean	Passing just east of Nukulaelae atoll,  Tuvalu (at 9°25′S 179°52′E / 9.417°S 179.867°E) Passing just west of the island of Cikobia,  Fiji (at 15°43′S 179°59′W / 15.717°S 179.983°W)
16°9′S 180°0′E / 16.150°S 180.000°E	Fiji	Islands of Vanua Levu, Rabi, and Taveuni
16°59′S 180°0′E / 16.983°S 180.000°E	Pacific Ocean	Passing just east of the island of Moala,  Fiji (at 18°33′S 179°57′E / 18.550°S 179.950°E) Passing just west of the island of Totoya,  Fiji (at 19°0′S 179°52′W / 19.000°S 179.867°W) Passing just east of the island of Matuku,  Fiji (at 19°10′S 179°47′E / 19.167°S 179.783°E)
60°0′S 180°0′E / 60.000°S 180.000°E	Southern Ocean
78°13′S 180°0′E / 78.217°S 180.000°E	Antarctica	Ross Dependency, claimed by  New Zealand

180° Meridian, Taveuni, Fiji

The meridian also passes between (but not particularly close to):

• the Gilbert Islands and the Phoenix Islands of  Kiribati;
• between North Island and the Kermadec Islands of  New Zealand;
• between the Bounty Islands and the Chatham Islands, also of  New Zealand.

The only place where roads cross this meridian, and where there are buildings very close to it, is in Fiji.

Software representation problems

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:

• The GeoJSON specification strongly suggests splitting geometries so that neither of their parts cross the antimeridian.^[2]
• In OpenStreetMap, areas (like the boundary of Russia) are split at the 180th meridian.

See also

• 179th meridian east
• 179th meridian west

Notes

1. The word antimeridian can also mean the meridian opposite to any given meridian. E.g. 20° west is the antimeridian of 160° east.
2. "RFC 7946 - The GeoJSON Format".