Parallel of latitude

A circle of latitude on the Earth is an abstract east–west circle connecting all locations around the earth (ignoring elevation) at a given latitude. Circles of latitude are often called parallels because they are parallel to each other – that is, any two circles are always the same distance apart. A location's position along a circle of latitude is given by its longitude. Circles of latitude are unlike circles of longitude, which all are great circles with the centre of Earth in the middle, as the circles of latitude get smaller as the distance from the Equator increases. Their length can be calculated by a common sine or cosine function. The 60th circle of latitude is half as long as the equator (disregarding Earth's minor flattening by 0.3%). A circle of latitude is perpendicular to all meridians.

The latitude of the circle is approximately the angle between the equator and the circle, with the angle's vertex at the Earth's centre. The equator is at 0°, and the North and South poles are at 90° north and 90° south respectively. The Equator is the longest circle of latitude and is the only circle of latitude which also is a great circle.

There are 89 integral (whole degree) circles of latitude between the equator and the Poles in each hemisphere, but these can be divided into more precise measurements of latitude, and are often represented as a decimal degree (e.g. 34.637°N) or with minutes and seconds (e.g. 22°14'26"S). There is no limit to how precisely latitude can be measured, and so there are an infinite number of circles of latitude on Earth.

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