From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.help Subject: Re: distance from Easter Island to Chile Date: Mon, 21 Apr 2014 12:35:31 +0200 Organization: Aioe.org NNTP Server Message-ID: <87sip7dl70.fsf@nl106-137-194.student.uu.se> References: <87mwfguasr.fsf@nl106-137-194.student.uu.se> <87mwfg823s.fsf@nl106-137-194.student.uu.se> <8761m3tq89.fsf@nl106-137-194.student.uu.se> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1398076824 16960 80.91.229.3 (21 Apr 2014 10:40:24 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 21 Apr 2014 10:40:24 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Mon Apr 21 12:40:20 2014 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WcBe6-0005Qg-TP for geh-help-gnu-emacs@m.gmane.org; Mon, 21 Apr 2014 12:40:19 +0200 Original-Received: from localhost ([::1]:48319 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WcBe6-0005CT-FJ for geh-help-gnu-emacs@m.gmane.org; Mon, 21 Apr 2014 06:40:18 -0400 Original-Path: usenet.stanford.edu!news.tele.dk!news.tele.dk!small.news.tele.dk!newsfeed.xs4all.nl!newsfeed4a.news.xs4all.nl!xs4all!news.stack.nl!aioe.org!.POSTED!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 54 Original-NNTP-Posting-Host: VVbyYd/iFZoeWNmD9i++cQ.user.speranza.aioe.org Original-X-Complaints-To: abuse@aioe.org User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) X-Notice: Filtered by postfilter v. 0.8.2 Cancel-Lock: sha1:IX9O3kYzj5fzzKXJB3cZTDxNbr0= Mail-Copies-To: never Original-Xref: usenet.stanford.edu gnu.emacs.help:205022 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:97287 Archived-At: giacomo.boffi@gmail.com writes: > Emanuel Berg writes: > >> giacomo.boffi@gmail.com writes: >> >>>> I get an answer of 4301.199 >>> >>> me too >> Provided the implementation is correct that's what >> you get with the Haversine method. > > (defun d2r (x) "degrees-to-radians is a macro, won't > work with mapcar..." (/ (* x pi) 180)) > > ; wolfram's alpha says (setq average-earth-radius > 6367.4447) > > ; there are sources that report different locations ; > for Santiago and Easter Island (setq santiago (mapcar > d2r '(33.4500 70.6667))) (setq easter_i (mapcar 'd2r > (27.1167 109.3667))) > > (defun haversines (p1 p2) "Returns a list with > sin^2(Delta_Lat/2) and sin^2(Delta_Lon/2). > http://en.wikipedia.org/wiki/Haversine" (flet ((d2 (x) > (/ x 2)) (p2 (x) (* x x))) (mapcar 'p2 (mapcar 'sin > (mapcar 'd2 (mapcar* '- p1 p2)))))) > > (defun central-angle (p1 p2) "Returns the central angle > between two locations on a sphere, using the haversine > formula. > http://en.wikipedia.org/wiki/Great-circle_distance#Computational_formulas > " (let* ( (hs (haversines p1 p2)) (hs-lat (car hs)) > (hs-lon (cadr hs)) (cos-lat1 (cos (car p1))) (cos-lat2 > (cos (car p2))) ) (* 2 (asin (sqrt (+ hs-lat (* > cos-lat1 cos-lat2 hs-lon))))))) > > (insert (format "\n%f" (* 6378.1 (central-angle > santiago easter_i)))) > > (insert (format "\n%f" (* average-earth-radius > (central-angle santiago easter_i)))) Can you see where the first attempt fails? That looks like the way I perceived the formula but I get a bit dizzy by all those mapcars - I have the subtraction in the opposite order but that might be how we supply the arguments. Get back to you - never ending story, this... -- underground experts united: http://user.it.uu.se/~embe8573