[Proj] proj-4.6.0 and BETA2007.gsb

Frank Warmerdam warmerdam at pobox.com
Wed Jan 23 13:57:10 EST 2008

Oliver Eichler wrote:
> No, it's not that simple.  I have attached a small C file.  I compile it
> with:
> gcc testpro.c -L/usr/lib64 -lproj -otestpro
> On the machine with the Proj4-4.6 version this will output (bad):
> 4487992.480929,5421613.273181
> On the machine with the Proj4-4.5 version this will output (good):
> 4488097.842111,5421724.742397


You are quite right.  I tried this out and determined that you need
to declare your WGS84 coordinate system as +datum=WGS84, not +ellps=WGS84.

The big change in PROJ 4.6.0 was that pj_transform() will no longer try to
apply datum shifts if either the source or destination lack a datum
declaration (either +datum, +towgs84 or +nadgrids).  Your WGS84 declaration
was "+proj=longlat +ellps=WGS84 +no_defs" which means a geographic
coordinate system on the WGS84 ellipsoid but it provides no datum shift
info to get to the WGS84 datum.

Sorry for not realizing this sooner.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org

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