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In geography, the latitude of a location on the Earth is the angular distance of that location north or south of the equator. The latitude is an angle, and is usually measured in degrees (marked with °). The equator has a latitude of 0°, the North pole has a latitude of 90° north (written 90° N or +90°), and the South pole has a latitude of 90° south (written 90° S or −90°). Together, latitude and longitude can be used as a geographic coordinate system to specify any location on the globe.

Curves of constant latitude on the Earth (running east-west) are referred to as lines of latitude. Each line of latitude is actually a circle on the Earth parallel to the equator, and for this reason lines of latitude are also known as known as circles of latitude or parallels. In spherical geometry, lines of latitude are examples of small circles, with the equator being a great circle.

Latitude is usually denoted by the Greek letter phi (φ). Though latitude is measured in degrees, minutes and seconds are often used for finer measurements. For example, the Eiffel Tower has a latitude of 48° 51′ 29″ N, where 48° refers to the number of degrees, 51′ refers to the number of minutes, and 29″ refers to the number of seconds. Alternatively, latitude may be measured entirely in degrees, e.g. 48.8583° N.

In astronomy, the latitude of a point on the Earth is approximately the angle between straight up (the zenith) and the noonday sun when it is at the equinox. In the traditional ecliptic coordinate system, the celestial latitude of any astronomical object is the angular distance of the object from the ecliptic. Thus the celestial latitude of the sun exactly 0°, and the celestial latitude of a pole star is approximately 90°.


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