Prime meridians

meridian passing through Greenwich, London

line of longitude, at which longitude is defined to be 0°

meridian line running through the Paris Observatory in Paris, France

Airy-0 is a crater inside the larger Airy Crater on Mars, whose location historically defined the Martian prime meridian. It is about 0.5 km (0.3 mile) across and lies within the dark region Sinus Meridiani, one of the early albedo features to be identified on Mars. In 2018, the IAU Working Group on Cartographic Coordinates and Rotational Elements recommended setting the longitude of the Viking 1 lander (47.95137° west) as the reference line. This definition maintains the position of the center of Airy-0 at 0° longitude, within the tolerance of current cartographic uncertainties.

line of longitude west of the Greenwich Meridian

line of longitude running through El Hierro (Ferro), Canary Islands

international prime meridian used for GPS and other systems

crater on Venus

meridian line in Poland

crater on Mercury

Proposed prime meridian

line of longitude