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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Gnomonic Charts - Usable Zones
From: Paul Hirose
Date: 2018 Jan 19, 00:49 -0800
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.