<P> Noon at one place is midnight at the other (ignoring daylight saving time and irregularly shaped time zones) and, with the exception of the tropics, the longest day at one point corresponds to the shortest day at the other, and midwinter at one point coincides with midsummer at the other . Sunrise and sunset do not quite oppose each other at antipodes due to refraction of sunlight . </P> <P> If the geographic coordinates (latitude and longitude) of a point on the Earth's surface are (φ, θ), then the coordinates of the antipodal point are (− φ, θ ± 180 °). This relation holds true whether the Earth is approximated as a perfect sphere or as a reference ellipsoid . </P> <P> In terms of the usual way these geographic coordinates are given, this transformation can be expressed symbolically as </P> <Dl> <Dd> x ° N / S y ° E / W ↦ x ° S / N (180 − y) ° W / E, </Dd> </Dl>

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