- Šárka Voráčová
A great circle, also known as an orthodrome, of a sphere is the intersection of the sphere and a plane that passes through the center point of the sphere. A great circle is the largest circle that can be drawn on any given sphere. The grear-circle distance or orthodromic distance is the shortest distance between two points on the sphere. Suppose two points on the sphere. Orthodromic distance is R.w [km], where R = 6378 km and Problem: Measure the shortest air distance from London (51°N 0°) to Buenos Aires (–34°S -60°W). As a reference surface use sphere with radius R = 6 378 km.
Compare the resulting distance with http://www.thetimenow.com/distance-calculator.php