The principle is straightforward, but in practice finding a reliable method of determining longitude took centuries and required the effort of some of the greatest scientific minds.Ī location's north–south position along a meridian is given by its latitude, which is approximately the angle between the equatorial plane and the normal from the ground at that location. Depending on the era, the absolute time might be obtained from a celestial event visible from both locations, such as a lunar eclipse, or from a time signal transmitted by telegraph or radio. Comparing local time to an absolute measure of time allows longitude to be determined. Scientifically precise local time varies with longitude: a difference of 15° longitude corresponds to a one-hour difference in local time, due to the differing position in relation to the Sun. Positive longitudes are east of the prime meridian, and negative ones are west.īecause of the Earth's rotation, there is a close connection between longitude and time measurement.
The prime meridian defines 0° longitude by convention the International Reference Meridian for the Earth passes near the Royal Observatory in Greenwich, south-east London on the island of Great Britain. Meridians are imaginary semicircular lines running from pole to pole that connect points with the same longitude. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Longitude ( / ˈ l ɒ n dʒ ɪ tj uː d/, AU and UK also / ˈ l ɒ ŋ ɡ ɪ-/) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body.
0 kommentar(er)
