Geographic coordinate system

Geographic coordinate system, Coordinate system to specify locations on Earth.

Geographic coordinate system image

A geographic coordinate system (GCS) is a coordinate system associated with positions on Earth (geographic position). A GCS can give positions: as spherical coordinate system using latitude, longitude, and elevation; as map coordinates projected onto the plane, possibly including elevation; as earth-centered, earth-fixed (ECEF) Cartesian coordinates in 3-space; as a set of numbers, letters or symbols forming a geocode.In geodetic coordinates and map coordinates, the coordinate tuple is decomposed such that one of the numbers represents a vertical position and two of the numbers represent a horizontal position. History The invention of a geographic coordinate system is generally credited to Eratosthenes of Cyrene, who composed his now-lost Geography at the Library of Alexandria in the 3rd century BC. A century later, Hipparchus of Nicaea improved on this system by determining latitude from stellar measurements rather than solar altitude and determining longitude by timings of lunar eclipses, rather than dead reckoning. In the 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically-plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles, off the coast of western Africa around the Canary or Cape Verde Islands, and measured north or south of the island of Rhodes off Asia Minor. Ptolemy credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day.Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead.
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