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Great Circles

  1. Mar 1, 2007 #1
    Could somebody please please explain how to work out the minimum distance between two co-ordinates on the earth, eg hobart(43 S,147 E) to Beijing (39 N, 117 E). Apparently there is a method incorporating great circles which finds min distant. If anyone knows the formula and could give me a quick explanation, would be much appreciated.
  2. jcsd
  3. Mar 1, 2007 #2


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    Yes, the shortest distance between two points on the surface of a sphere is along a "great circle" which is a circle having the center of the sphere as its center. The length of an arc of radius R and subtending central angle [itex]\theta[/itex], in radians, is R[itex]/theta[/itex]. If [itex]\theta[/itex] is in degrees that is [itex]R\theta (\pi/180)[/itex]. Here R is the radius of the earth and you will need to work out the angle [itex]\theta[/itex] from the latitude and longitude.
  4. Mar 1, 2007 #3
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