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[Pkg-octave-devel] Bug#415341: marked as done (octave-forge: azimuth.m gives incorrect values)

Your message dated Thu, 27 Sep 2007 12:38:51 +0200
with message-id <1190889531.20686.10.camel@localhost>
and subject line [Pkg-octave-devel] Bug#415341: octave-forge: azimuth.m gives incorrect values
has caused the attached Bug report to be marked as done.

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--- Begin Message --- 
Package: octave-forge
Version: 2006.07.09+dfsg1-8
Severity: normal
Tags: patch

*** Please type your report below this line ***
The calculation in mapping/azimuth.m in both the 2.1 and 2.9 branches of 
octave-forge gives incorrect values.  A correct version of the 
calculation is given at http://williams.best.vwh.net/avform.htm#Crs

Instead of the current calculation:
<       az = rad2deg(acot((sin(a) * cot(b) - cos(a) * cos(C)) / \
<                         sin(C)));

the calculation should be:
>       az=rad2deg(mod(atan2(sin(C)*sin(b), \
>                            sin(a)*cos(b)-cos(a)*sin(b)*cos(C)),\
>                      2*pi));

If azimuth.m is actually doing the right thing, then perhaps its 
documentation needs changing - as I read it, it calculates the angle of 
the great circle between the two points.  This is not what the current 
calculation does.

Apologies if I've got anything wrong - I'm fairly new to spherical 
geometry - do email to discuss this if necessary.


-- System Information:
Debian Release: 4.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.17.061206.1
Locale: LANG=en_GB, LC_CTYPE=en_GB (charmap=ISO-8859-1)

Versions of packages octave-forge depends on:
ii  octave2.1-forge       2006.03.17+dfsg1-3 Contributed functions from the 
GNU

octave-forge recommends no packages.

-- no debconf information

Attachment: pgpztHjPU2Ytg.pgp
Description: PGP signature


--- End Message ---
--- Begin Message --- 
Am Sonntag, den 18.03.2007, 22:25 +0100 schrieb Rafael Laboissiere:
> package octave-forge
> tags 415341 upstream
> thanks
> 
> * Tom Wright <tew24@esc.cam.ac.uk> [2007-03-18 15:56]:
> 
> > The calculation in mapping/azimuth.m in both the 2.1 and 2.9 branches of 
> > octave-forge gives incorrect values.  A correct version of the 
> > calculation is given at http://williams.best.vwh.net/avform.htm#Crs
> > 
> > Instead of the current calculation:
> > <       az = rad2deg(acot((sin(a) * cot(b) - cos(a) * cos(C)) / \
> > <                         sin(C)));
> > 
> > the calculation should be:
> > >       az=rad2deg(mod(atan2(sin(C)*sin(b), \
> > >                            sin(a)*cos(b)-cos(a)*sin(b)*cos(C)),\
> > >                      2*pi));
> > 
> 
> There is a new version of azimut.m in the CVS repository of octave-forge [1].
> Could you please check if that version does the correct calculation?
> 
> [1] http://octave.cvs.sourceforge.net/octave/octave-forge/extra/mapping/inst/azimuth.m?revision=1.2

After 6 months without an answer, I assume this bug to be fixed. If not,
please try up-to-date "mapping" package, available from octave-forge's
website via Octave's pkg.m.

	Thomas

--- End Message ---
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