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great circle distance

The length of the shorter arc of the great circle joining two points on a spherical earth. It is usually expressed in nautical miles.

This is the shortest distance between two points on a spherical earth.

(If we take into account the very slightly pear shape of the real earth, then technically the shortest distance between two points is the ellipsoidal distance which accounts for the earth shape. The differences between Great Circle and Ellipsoidal distance is usually small but can be up to 7 or 8 miles for a distance of 3,000 miles, depending on the actual route.)




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