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    Re: Sun sights by 13 year-olds
    From: Michael Dorl
    Date: 2004 Sep 27, 11:55 -0500

    At 10:28 AM 9/27/04 -0400, Charles Seitz   wrote:
    >Obviously, the next step would be to rewrite the software to accept data
    >from additional sightings and calculate the circle intersections.
    >That's easier said than done.  Many hours of web searching have failed
    >to reveal any equations to do this.  I can't believe that during several
    >thousand years of spherical geometry study, someone has not solved this
    >problem.  It might be a horrendous problem but the solution is out there
    >somewhere.  GPS is based on a similar concept.
    >I'm not a mathematician and will not attempt to derive the equations.
    >I'll look into solving this problem numerically.  But, that is a brute
    >force approach that is not particularly satisfying from an aesthetic
    I conducted a similar search some years ago without much success so I sat
    down and figured it out.
    The biggest problem is paying due regard to the quadrant of the results of
    the various arc whatever functions.
    If you like, I could send you a short paper outlining the procedure.  I
    don't think I can post it to the list since
    it contains some figures.  I also have a windows application that will
    compute the equal altitude circle
    intersections and optionally display the circles on a world map.
    Mike Dorl

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