Prime Meridian (redirected from prime meridians)

prime meridian, meridian that is designated zero degree (0°) longitude, from which all other longitudes are measured. By international convention, it passes through the original site of the Royal Observatory in Greenwich, England; for this reason, it is sometimes called the Greenwich meridian. Universal time, the standard basis for determining time throughout the world, is civil time measured at the prime meridian.

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prime meridian

the 0° meridian from which the other meridians or lines of longitude are calculated, usually taken to pass through Greenwich

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prime meridian [′prīm mə‚rid·ē·ən]

(geodesy)

The meridian of longitude 0°, used as the origin for measurement of longitude; the meridian of Greenwich, England, is almost universally used for this purpose.

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Prime Meridian 

(or zero meridian), the terrestrial meridian that passes through Greenwich, the site of the old Royal Observatory. The prime meridian is the starting point for the calculation of geographic longitude and is the central meridian of the zero time zone. Local mean solar time at the prime meridian is widely used in astronomy (so-called universal time).