The angle in degrees that indicates the east-west position of a point on the earth´s surface from the Greenwich meridian. A line of longitude, also called meridian, is half of a circle on the surface of the earth that passes through the north pole and the south pole. The Greenwich meridian, defined as 0° longitude, is the line of longitude that passes through Greenwich, a suburb of London, England.In the case of the point P on the line of longitude shown in red, the longitude is the angle between the radii OG and OE, in which O is the center of the earth, G is on the Greenwich meridian, and E is the intersecting point of the longitude and the equator.

Related Terms: azimuth (three-dimension), latitude, meridian

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