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Meridian (geography) Meridians run between the North and South poles. In geography and geodesy, a meridian is the locus connecting points of equal longitude, which is the angle (in degrees or other units) east or west of a given prime meridian (currently, the IERS Reference Meridian ). [1] In other words, it is a line of longitude.
Meridian (astronomy) The meridian on the celestial sphere. An observer's upper meridian, a semicircle contains their zenith and both celestial poles; the observer's local meridian is the semicircle that passes through their zenith and the north and south points of their horizon. In astronomy, the meridian is the great circle passing through the ...
Prime meridian. A prime meridian is an arbitrarily -chosen meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great circle. This great circle divides a spheroid, like Earth, into two hemispheres ...
Figure 1. This BLM map depicts the principal meridians and baselines used for surveying states (colored) in the PLSS.. The following are the principal and guide meridians and base lines of the United States, with the year established and a brief summary of what areas' land surveys are based on each.
Meridian (geography), a longitude line, i.e. a line of constant longitude, or in other words an imaginary arc on the Earth's surface from the North Pole to the South Pole. Meridian arc, the distance between two points with the same longitude. Prime meridian, origin of longitudes. Principal meridian, arbitrary meridians used as references in ...
Meridian arc. In geodesy and navigation, a meridian arc is the curve between two points on the Earth's surface having the same longitude. The term may refer either to a segment of the meridian, or to its length . The purpose of measuring meridian arcs is to determine a figure of the Earth . One or more measurements of meridian arcs can be used ...
Meridian altitude is the simplest calculation of celestial navigation, in which an observer determines his latitude by measuring the altitude of an astronomical object at the time of its meridian contact. A meridian contact is the moment when the object contacts the observer's meridian, i.e. the imaginary line running north–south and through ...
The Greenwich meridian is a prime meridian, a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. [1] From 1884 to 1974, the Greenwich meridian was the international standard prime meridian, used worldwide for timekeeping and navigation. The modern standard, the IERS Reference Meridian, is based ...