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Calculating Lat/Lng X miles from point

I don't know how to ask the question, so I'll explain my requirments -- I hope I'm in the right site :)

  • Let's assume that a person is standing somewhere on Earth and his coordinates are: x long, y lat.
  • Let's assume that if the person is facing north he is on 0°, south is 180°, north-west is 315° ... etc. (unless there is some standard that I'm not aware of)
  • Let's assume that the person can walk in a straight line from his position on the direction he's facing until he completes a full round around the Globe; i.e. return to his starting position.

My question is, what is the equation/set of equations to be used to calculate the person's coordinates (longitude and latitude) every 50, 100, 300 ... etc. kilometers until a full round is done?

Thanks in advance.

marked as duplicate by whuber Dec 6 '11 at 17:54

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