From: Eli Zaretskii <eliz@gnu.org>
To: help-gnu-emacs@gnu.org
Subject: Re: distance from Easter Island to Chile
Date: Sun, 20 Apr 2014 09:28:23 +0300 [thread overview]
Message-ID: <83sip8fraw.fsf@gnu.org> (raw)
In-Reply-To: <87mwfguasr.fsf@nl106-137-194.student.uu.se>
> From: Emanuel Berg <embe8573@student.uu.se>
> Date: Sun, 20 Apr 2014 02:03:32 +0200
>
> (defun distance (l1-r f1-r l2-r f2-r)
> (interactive)
> (let ((l1 (degrees-to-radians l1-r))
> (f1 (degrees-to-radians f1-r))
> (l2 (degrees-to-radians l2-r))
> (f2 (degrees-to-radians f2-r)) )
> (* 2 6378.1 ; Earth's radius
> (asin
> (sqrt
> (+ (sin2 (/ (- f2 f1) 2))
> (* (cos f2) (cos f1) (sin2 (/ (- l2 l1) 2))) ))))))
This is inaccurate (Earth is not a sphere). See
http://en.wikipedia.org/wiki/Geodesics_on_an_ellipsoid for some theory
and more accurate formulas. A very accurate method is described in
http://en.wikipedia.org/wiki/Vincenty%27s_formulae (you need the
"inverse problem").
next prev parent reply other threads:[~2014-04-20 6:28 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-20 0:03 distance from Easter Island to Chile Emanuel Berg
2014-04-20 3:55 ` Frank Stutzman
2014-04-20 15:14 ` Emanuel Berg
2014-04-20 22:39 ` giacomo.boffi
[not found] ` <mailman.19957.1398033917.10748.help-gnu-emacs@gnu.org>
2014-04-21 1:40 ` Emanuel Berg
2014-04-21 1:50 ` Emanuel Berg
2014-04-21 9:45 ` giacomo.boffi
[not found] ` <mailman.19981.1398073560.10748.help-gnu-emacs@gnu.org>
2014-04-21 10:35 ` Emanuel Berg
2014-04-21 10:50 ` Emanuel Berg
2014-04-23 2:49 ` Emanuel Berg
2014-04-21 2:16 ` Emanuel Berg
2014-04-20 4:44 ` Barry Margolin
2014-04-20 15:06 ` Emanuel Berg
2014-04-20 6:28 ` Eli Zaretskii [this message]
[not found] ` <mailman.19905.1397975330.10748.help-gnu-emacs@gnu.org>
2014-04-20 7:01 ` Barry Margolin
2014-04-20 7:48 ` Eli Zaretskii
2014-04-20 10:26 ` Thorsten Jolitz
2014-04-20 11:03 ` Eli Zaretskii
2014-04-20 15:22 ` Emanuel Berg
2014-04-21 6:04 ` Emanuel Berg
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