On Mon, 2005-08-08 at 06:31, Durk Talsma wrote: > On Sunday 07 August 2005 15:54, Erik Hofman wrote: > > Erik Hofman wrote: > > > Is this correct or am I missing something? > > > > I just realized that you also need to adjust for day-of-year to > > compensate for the out-of-center rotation that causes long days (and > > nights) for both polar areas. > > > Just looking through your mails quickly, it looks like you also need to > compensate for the fact the the earth's rotation axis is tilted by about 23 > degrees, [plus] the earth's orbit around the sun > is not a perfect sphere, but an ellipse.
Durk is quite right. It's non-trivial, but dealing with all these issues is not really a problem. I'm in the middle of doing it myself, but have just only just got back from a week on vacation. My main interest is in removing the use of Xearth's "find the point on the planet where the sun is overhead" routine and replacing it with the more obvious "what is the current altitude and azimuth of the sun seen from a given location". Doing that will make all the solar (and lunar) astronomy code use standard algorithms from Peter Duffett-Smith's books and thus make sure there can be no problems with Xearth's non-GPL code causing trouble for FlightGear. Steve. _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
