180th meridian
The 180th meridian, also known as the antimeridian, is the line of longitude located exactly 180 degrees both east and west of the prime meridian. In geographical coordinate systems, longitude at this line can be designated as either east or west. Together, the prime meridian and the 180th meridian form a great ellipse that splits the Earth into the Western and Eastern Hemispheres.
This meridian primarily traverses the open waters of the Pacific Ocean, but it also crosses land in Russia, Fiji, and Antarctica. Its most significant function is serving as the foundation for the International Date Line, which deviates from the meridian in several places to ensure consistent dates within the territories of Russia, the United States, Kiribati, Fiji, and New Zealand. From the North Pole southward, the meridian passes through various regions, including the Aleutian Island chain (part of U.S. territory), and between island groups such as the Gilbert and Phoenix Islands of Kiribati, as well as between New Zealand’s North Island and its Kermadec Islands, and between the Bounty and Chatham Islands. The only locations where roads cross this meridian are in Fiji and Russia. Fiji has multiple roads and some buildings situated very close to the line, while Russia has three roads in the Chukotka Autonomous Okrug.
The 180th meridian also presents notable challenges in digital mapping. Many geographic software libraries and data formats project the world as a rectangle split exactly at this meridian, complicating tasks like representing areas or lines that cross it. For instance, the GeoJSON specification recommends splitting geometries so no part crosses the antimeridian. In OpenStreetMap, areas such as Russia’s boundary are split at this line, and navigation across it is not supported by any directions engine. QGIS may display lines and polygons in a wrapped manner if they cross the 180th meridian, and in Google Maps, navigation on Fiji’s Taveuni island is impossible when crossing the meridian, functioning only on one side.
- type
- Geographical line of longitude
- also_known_as
- Antimeridian
- location
- Pacific Ocean, Russia, Fiji, Antarctica
- function
- Basis for the International Date Line
- crossed_by_roads
- Fiji and Russia
Lore & Background
The 180th meridian, also known as the antimeridian, is the line of longitude located exactly 180 degrees both east and west of the prime meridian. In geographical coordinate systems, longitude at this line can be expressed as either east or west. Together, the prime meridian and the 180th meridian form a great ellipse that divides the planet into the Western and Eastern Hemispheres. On Earth, this meridian runs predominantly through the open waters of the Pacific Ocean. However, it also crosses landmasses in Russia, Fiji, and Antarctica. A critical function of this meridian is its role as the basis for the International Date Line, which zigzags around national borders to ensure date consistency within the territories of Russia, the United States, Kiribati, Fiji, and New Zealand. The meridian passes between, though not particularly close to, several island groups: the Aleutian Island chain of US territory, the Gilbert Islands and Phoenix Islands of Kiribati, North Island and the Kermadec Islands of New Zealand, and the Bounty Islands and Chatham Islands of New Zealand. The only locations where roads cross this meridian are in Fiji and Russia. Fiji features several such roads and some buildings situated very close to the line, while Russia has three roads in the Chukotka Autonomous Okrug.
Reader's Guide
The 180th meridian is significant as the basis for the International Date Line, which adjusts date boundaries to avoid splitting countries. It also presents software representation problems: many geographic libraries split the world at this meridian, making tasks like representing areas or lines across it non-trivial. For example, GeoJSON suggests splitting geometries to avoid crossing the antimeridian, OpenStreetMap splits areas like Russia's boundary, and navigation across the meridian is not possible in Google Maps on Taveuni island, Fiji. Only in Fiji and Russia do roads cross this meridian.
Did You Know?
- The 180th meridian is also called the antimeridian.
- It passes through land in Russia, Fiji, and Antarctica.
- Only Fiji and Russia have roads that cross this meridian.
- In Google Maps, navigation is not possible across the 180th meridian on Taveuni island, Fiji.
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