[Proj] Switch utm from tmerc to etmerc

Even Rouault even.rouault at spatialys.com
Mon Oct 26 03:48:29 EST 2015

Le lundi 26 octobre 2015 00:09:10, Roger Bivand a écrit :
> Charles Karney <charles.karney <at> sri.com> writes:
> > This change has now been made to the master branch of the source.  The
> > "utm projection" now follows the NGA recommendation and uses etmerc
> > instead of tmerc (which is less accurate).  You can expect small
> > (typically < 1mm, except at high latitudes) changes in the results for
> > the utm projection.
> While correcting wrong parameterisations is good, here we are doing what
> the mooted metacrs definitions were trying to avoid, that is altering
> in-place code without user-facing versioning. Different versions (by
> commit hashes now) of the underlying code will now give different answers,
> so re-running an analysis with the same data and apparently the same code
> in software linking to proj will give different answers, without the user
> necessarily being able to re-instate the earlier relationship. It would be
> great to bear in mind the fact that research does need to be reproducible
> (data from times before this correction was known don't need to be obliged
> to use it). I guess we have to assume that users really read commit logs
> and NEWS files.


I'm not in the business of reproducible research but I guess that if you want 
things to be perfectly reproducible you'd have to specify all the environment: 
exact software versions, probably with their compilation options and versions 
of their dependencies, OS version, and possibly hardware that was used.


> Roger
> >    --Charles
> > 
> > On 10/06/2015 11:19 AM, Charles Karney wrote:
> > > Reposted from
> > > 
> > >    https://github.com/OSGeo/proj.4/issues/316
> ...
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