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<p>I'm imagining a post near-apocalyptic world where the near-future
MAGAmorlocks watch ElonMuskishEloi flying machines traveling high
in the sky (with or without contrails) and set their crude
sextants on the problem of shooting a trajectory and from that
guestimating which known megaCity Enclaves they are traveling
between. <br>
</p>
<p>Thanks to Barry for the Gnomonic projection prompt... I seem to
remember that the Gnomonic is the earliest known map projection
and is derived from the traces of time-arcs cast by the sundial's
gnomon.<br>
</p>
<p>Am I wrong that Rhumblines are reasonable approximations of great
circles, with the added convenience of providing a very simple
navigational technique (constant angle to north)?</p>
<p> <a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Rhumbline_network">https://en.wikipedia.org/wiki/Rhumbline_network</a></p>
<p>turning the problem inside out (Ed Angel/SteveG), we have the
rectilinear lens?</p>
<p> <a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Rectilinear_lens">https://en.wikipedia.org/wiki/Rectilinear_lens</a></p>
<p><br>
</p>
<div class="moz-cite-prefix">On 9/19/21 7:20 PM, Barry MacKichan
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1568EAF3-7A2E-4A01-BC48-14121ED91278@mackichan.com">
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<div dir="ltr">In the northern hemisphere a great circle route
between two points with the same latitude will be north of the
parallel, so if the latitudes are close, the great circle will
arch above the straight line (for most map projections that keep
“parallels” parallel). A gnomonic projection of the world
centered on Charlotte or Honolulu would show the great circle
route as a straight line. I’m sure none of those were printed,
but I thought I might find a site that allowed the user to
select a tangent point (Charlotte or Honolulu) and then show the
map. The closest I got was <a
href="https://bl.ocks.org/mbostock/3795048"
moz-do-not-send="true">https://bl.ocks.org/mbostock/3795048</a> and <a
href="https://observablehq.com/@d3/gnomonic"
moz-do-not-send="true">https://observablehq.com/@d3/gnomonic </a>. It
turns out that d3.js, a graphics library has a function
geoGnomonic().</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">—Barry</div>
<div dir="ltr"><br>
<div dir="ltr">Sent from my iPad</div>
<div dir="ltr"><br>
<blockquote type="cite">On Sep 19, 2021, at 3:50 PM, Frank
Wimberly <a class="moz-txt-link-rfc2396E" href="mailto:wimberly3@gmail.com"><wimberly3@gmail.com></a> wrote:<br>
<br>
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<blockquote type="cite">
<div dir="ltr">
<div dir="auto">Not to change the subject but...
<div dir="auto"><br>
</div>
<div dir="auto">A large airliner recently, 15 minutes ago,
flew over Santa Fe headed west. My Flight Radar app
tells me that it's a Boeing 777 going from Charlotte to
Honolulu at an altitude of 38000 feet. I wouldn't have
thought that Santa Fe was on a great Circle route
between those two cities. But maybe it is.<br>
<br>
<div data-smartmail="gmail_signature" dir="auto">---<br>
Frank C. Wimberly<br>
140 Calle Ojo Feliz, <br>
Santa Fe, NM 87505<br>
<br>
505 670-9918<br>
Santa Fe, NM</div>
</div>
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