Geographic coordinate system

Geographic Coordinate System

A Geographic Coordinate System is a coordinate system that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are often chosen such that one of the numbers represents a vertical position and two or three of the numbers represent a horizontal position; alternatively, a geographic position may be expressed in a combined three-dimensional Cartesian vector.

Overview

A common choice of coordinates is latitude, longitude and elevation. To specify a location on a plane requires a map projection.

Latitude and Longitude

Latitude is a measurement on a globe or map of location north or south of the Equator. Technically, there are different kinds of latitude—geocentric, astronomical, and geographic (or geodetic)—but there are only minor differences between them.

Longitude is a measurement east or west of the prime meridian at Greenwich, the specially designated imaginary north-south line that passes through both geographic poles and Greenwich, London.

Map Projections

A map projection is a way to flatten a globe's surface into a plane in order to make a map. This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane.

See Also

• Cartesian coordinate system
• Geodetic system
• Geocentric coordinate system
• Geographic information system
• Global Positioning System

References

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  Map showing latitude and longitude lines
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  Latitude and longitude graticule on a sphere