On
Earth, the prime and 180th meridians form a
great circle that divides the planet into the
Western and
Eastern Hemispheres. The antimeridian passes mostly through the open waters of the
Pacific Ocean but also runs across land in
Russia,
Fiji, and
Antarctica. An important function of this meridian is its use as the basis for the
International 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 the
North Pole of the Earth and heading south to the
South Pole, the 180th meridian passes through:
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 the
Chukotka Autonomous Okrug.
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.
QGIS may present lines and polygons in a wrapped way if they cross the 180 meridian.