[FRIAM] Great Circle
Steve Smith
sasmyth at swcp.com
Mon Sep 20 11:19:25 EDT 2021
Answering my own earlier question (with props) it seems that a (smooth)
globe and piece of string would be good support for an intuitive
approach. My sister made a "hanging string lampshade" in 3rd grade by
wrapping cotton string soaked in glue around a large balloon and letting
it dry. I inherited it when she went into middle school and was "too
cool" for it anymore. I would lay in bed and stare at it, remembering
the challenges (I helped wrap the string) of getting the slick string to
do *anything* but following near-great-circles. The shadows it cast on
the walls (and furniture) might have been my first awareness of
projective geometry... I abandoned it when I went to college.
I assume (REC?) that early age-of-exploration navigators were more
constrained by trade-winds and convenient resupply/port-of-call than
great-circles, though misunderstanding spherical geometry would be very
inconvenient.
I also believe that Polynesian stick charts would have great-circleness
(or more-to-the-point shortest time paths) built into them by their
nature, not any arcane understanding of spherical (ellipsoidal)
geometry. I'm sure they have been studied quite thoroughly.
On 9/19/21 3:36 PM, Stephen Guerin wrote:
> In the early 90s, my expat friends in Beijing would often debate which
> were the closer US Cities to Beijing by eyeballing the globe - wish we
> had this too for easy lookup back then. Of course, we could have used
> lat/longs and calculated haversine distances but we had pints to drink
> - and frankly it would have been difficult for me to find the
> algorithm in the nascent web back then ;-)
>
> Beijing (PEK) Great Circle Distances for 10 US cities
> <https://www.greatcirclemap.com/globe?routes=%20PEK-SEA%2C%20PEK-LAX%2C%20PEK-DET%2C%20PEK-SAN%2C%20PEK-MSP%2C%20PEK-YYZ%2C%20PEK-EWR%2C%20PEK-ORD%2C%20PEK-ANC%2C%20PEK-BGR%2C%20PEK-HNL>
>
> image.png
>
>
> _______________________________________________________________________
> Stephen.Guerin at Simtable.com <mailto:stephen.guerin at simtable.com>
> CEO, Simtable http://www.simtable.com <http://www.simtable.com/>
> 1600 Lena St #D1, Santa Fe, NM 87505
> office: (505)995-0206 mobile: (505)577-5828
> twitter: @simtable
> z <http://zoom.com/j/5055775828>oom.simtable.com <http://oom.simtable.com>
>
>
> On Sun, Sep 19, 2021 at 3:22 PM Frank Wimberly <wimberly3 at gmail.com
> <mailto:wimberly3 at gmail.com>> wrote:
>
> That gives a good view, Stephen. Hawaii is farther south than I
> thought. Thanks.
>
> ---
> Frank C. Wimberly
> 140 Calle Ojo Feliz,
> Santa Fe, NM 87505
>
> 505 670-9918
> Santa Fe, NM
>
> On Sun, Sep 19, 2021, 3:19 PM Stephen Guerin
> <stephen.guerin at simtable.com <mailto:stephen.guerin at simtable.com>>
> wrote:
>
> I was going to post this similar site but Ed beat me with his
> :-) This one also has a globe view...
>
> https://www.greatcirclemap.com/globe?routes=CLT-HNL
> <https://www.greatcirclemap.com/globe?routes=CLT-HNL>
> _______________________________________________________________________
> Stephen.Guerin at Simtable.com <mailto:stephen.guerin at simtable.com>
> CEO, Simtable http://www.simtable.com <http://www.simtable.com/>
> 1600 Lena St #D1, Santa Fe, NM 87505
> office: (505)995-0206 mobile: (505)577-5828
> twitter: @simtable
> z <http://zoom.com/j/5055775828>oom.simtable.com
> <http://oom.simtable.com>
>
>
> On Sun, Sep 19, 2021 at 2:03 PM Frank Wimberly
> <wimberly3 at gmail.com <mailto:wimberly3 at gmail.com>> wrote:
>
> Thanks, Ed. That's useful.
>
> ---
> Frank C. Wimberly
> 140 Calle Ojo Feliz,
> Santa Fe, NM 87505
>
> 505 670-9918
> Santa Fe, NM
>
> On Sun, Sep 19, 2021, 1:54 PM Edward Angel
> <angel at cs.unm.edu <mailto:angel at cs.unm.edu>> wrote:
>
> Close:
> https://www.airmilescalculator.com/distance/clt-to-hnl/
> <https://www.airmilescalculator.com/distance/clt-to-hnl/>
> _______________________
>
> Ed Angel
>
> Founding Director, Art, Research, Technology and
> Science Laboratory (ARTS Lab)
> Professor Emeritus of Computer Science, University of
> New Mexico
>
> 1017 Sierra Pinon
> Santa Fe, NM 87501
> 505-984-0136 (home) angel at cs.unm.edu
> <mailto:angel at cs.unm.edu>
> 505-453-4944 (cell) http://www.cs.unm.edu/~angel
> <http://www.cs.unm.edu/~angel>
>
>> On Sep 19, 2021, at 1:48 PM, Frank Wimberly
>> <wimberly3 at gmail.com <mailto:wimberly3 at gmail.com>> wrote:
>>
>> Not to change the subject but...
>>
>> 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.
>>
>> ---
>> Frank C. Wimberly
>> 140 Calle Ojo Feliz,
>> Santa Fe, NM 87505
>>
>> 505 670-9918
>> Santa Fe, NM
>>
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