I'm trying to draw a circle (actually a great circle) on an equirectangular map to archive something like this https://i.sstatic.net/7EliU.png (from here).

So I have the lat/lon coordinates of the center of the circle on the surface of the sphere and I already have the coordinates (the position of the sun) and would like to have a function describing the border of this circle on an equirectangular map by using these coordinates.

I think the answer mentioned above fits my needs, but sadly I don't understand it entirely. Is there an easy way to do this?

  • What software do you want to use? And what part of the other answer (I assume you mean gis.stackexchange.com/questions/52949/…) don't you understand?
    – Jake
    Commented Oct 15, 2013 at 20:39
  • Sorry, the editor removed my link to that question. Anyway, it's not a software specific question. I want to do this calculation in Java but that's not important. Regarding the the answered I'm actually not really sure whether it is what I'm looking for. I have latitude and longitude of the center and need to calculate the great circle. Sorry, but this is really not my cup of tea.
    – ratatosk
    Commented Oct 15, 2013 at 20:51
  • 1
    If your circle is centered at (lon0, lat0), you can plot the great circle using lat = atan(-cos(lon-lon0)/tan(lat0))
    – Jake
    Commented Oct 15, 2013 at 21:20
  • Thank you very much! I finally managed to do what I wanted!
    – ratatosk
    Commented Oct 16, 2013 at 12:30


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