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    Re: Gnomonic Charts - Usable Zones
    From: Paul Hirose
    Date: 2018 Jan 19, 00:49 -0800

    On 2018-01-18 23:43, Bob Goethe wrote:
    > Is there another equation (or set of equations) that will let me say, "If I 
    start from a certain latitude and longitude, and travel 200 nm on a course of 
    θ°, what will be my latitude and longitude at the end of my journey?"  In a 
    sense, I think my question is "Can I plan ahead my waypoints for a great 
    circle route WITHOUT using a gnomonic chart?"
    
    Yes, the Bygrave method can produce the coordinates of the point at a
    given great circle distance and bearing from the departure point. You
    simply swap the pole and observer and work the problem like a sight
    reduction. It's very similar to star identification, which I recently
    explained here:
    
    http://fer3.com/arc/m2.aspx/Star-identification-via-Bygrave-formulas-Hirose-jan-2018-g41160
    
    For instance, if you put the "star" at altitudes 85°, 80°, etc., points
    are generated at 300, 600 ... miles from the starting point on a great
    circle.
    

       
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