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Great Circle The intersection of a plane and a sphere (the earth) on the surface of the sphere is a circle. If the plane passes through the center of the sphere the circle is a great circle. The shortest distance between two points on the surface of a spherical earth is the segment of the great circle passing between the two points. For any angular segment of a great circle on the earth 1° = 60 nmi. (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.)

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