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  1. Mick West

    Mick West Administrator Staff Member

    20170507-181006-wrhy8.

    https://www.metabunk.org/flat/

    I wrote a flat vs. globe route simulator over the weekend. It shows the shortest route between two points on a globe, a flat earth, and an standard map. The lengths of each route are calculated for the globe and the flat earth.

    (Note: does not work on mobile devices, works best with Chrome)
     
    Last edited: May 9, 2017
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  2. Amber Robot

    Amber Robot Member

    What kind of projection are you calling "standard"? Mercator? What does that route mean, if anything?
     
  3. Mick West

    Mick West Administrator Staff Member

    It's equirectangular, it's the map you see there.

    The route shown by the yellow line is similar to a rhumb line course, which is a reasonable route for short distance navigation. You just follow a fixed compass heading. It's longer than a great circle, but the great circle route needs constant changes to compass heading.

    A straight line on a Mercator map is a true rhumb line, but you can't get the whole world onto a Mercator map.
    905px-Mercator_projection_SW.

    The Mercator map is essentially evidence of the globularity of the world, as if the world were flat the map would shrink at the bottom, and not expand.
     
    Last edited: May 8, 2017
  4. Mick West

    Mick West Administrator Staff Member

    This page has good explanations and illustrations of the differences between a rhumb line on a Mercator vs. equirectangular (same as Equidistant cylindrical) maps.
    http://www.progonos.com/furuti/MapProj/Normal/CartProp/Rhumb/rhumb.html 20170508-172639-hw9qr.
    20170508-172704-bhpvf.
    (Note there's 5° missing off the top and bottom of this mercator projection)

    True Rhumb lines might be a good addition to the simulator at some point. But I'm done programming for a while.
     
    Last edited: May 9, 2017
  5. Amber Robot

    Amber Robot Member

    Great explanation! Thanks.