FYI - relevant followup.
Markus
---------- Forwarded message ----------
From: Frank Warmerdam <warmerdam@pobox.com>
Date: Wed, Feb 22, 2012 at 5:32 PM
Subject: Re: [Proj] Proj Release
To: proj@lists.maptools.org
On 12-02-22 07:18 AM, Roger Bivand wrote:
I certainly feel that this change is premature. All I can see on the web page is
a note that "refinement of datum shifting support" may happen sometime. I don't
think that removing a functioning mechanism used by many - not just in GRASS,
also in R/rgdal - without clear RFC handling, and without fallbacks or
transitional mechanisms - is justified. What will happen is that a release of
PROJ now, without this "mistake" being corrected, will mean that scripts running
a given +init=epsg:<> may end up with different results, not because the current
EPSG file is buggy and needed fixing. When spatial data are used analytically,
as in the GRASS and R communities, reproducibility really does matter.I suggest that this needs an RFC, and should be held off until some 4.9.0, if
the RFC process concludes that switching from +datum= is on balance justified.
The alternative is to advise users to stay on 4.7, but many cannot control their
build trains well enough for this to be feasible.
Roger,
I am convinced. I will modify the OGRSpatialReference::exportToProj4()
code to restore the old behavior and regenerate the EPSG init file for
PROJ.4. I'll notify the list when it is ready. I have been quite slack
about the RFC process for PROJ.4.
In the long term I think it is wrong for the epsg init file to generate
+datum widely when it is likely it will not expand to the actual datum
translation defined by EPSG.
I have also been thinking in the back of my head that we should support
some "documentation only" flags in PROJ.4 definitions. For instance the
IGNF init file uses the +title= option to capture a coordinate system
name. I'm not sure what software actually uses that. We might want to
also add +epsg_pcs=n and +epsg_gcs=n directives relating the projected
and geographic coordinate system back to EPSG for easier identification
in various contexts.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://home.gdal.org/warmerda
and watch the world go round - Rush | Geospatial Software Developer
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