Longitude

Earth-centered ecliptic coordinates

Geography

The geographical longitude is the angle between a location on the Earth's surface and the prime meridian which runs through Greenwich in England. Longitude is measured in degrees. The 180 degrees to the west of the prime meridian are known as the Western Longitudes, and those to the east as the Eastern Longitudes.

The combination of geographical longitude and geographical latitude gives the precise location of any particular place on the Earth's surface.

Astronomy

When both the ecliptic longitude (also called the solar or celestial longitude) and latitude are known, it is possible go give an exact position for any point on the celestial sphere. Ecliptic longitude measures the angular distance of an object along the ecliptic from the primary direction. Like Right Ascension in the Equatorial System, the primary direction (0° ecliptic longitude) points from the Earth towards the Sun at the vernal equinox of the Northern Hemisphere. Because it is a right-handed system, ecliptic longitude is measured positive eastwards in the fundamental plane (the ecliptic) from 0° to 360°. This ecliptic longitude is the distance between the object to the vernal equinox.

See also

• Coordinate System

Weblinks

• Wikipedia: Ecliptic coordinate system
• How is Latitude different than Longitude? (MooMooMath and Science; 2,2 min)