[Proj] ERROR 6: No translation for Double_Stereographic to PROJ.4 format is known.
Mikael.Rittri at carmenta.com
Thu Apr 2 06:46:52 EST 2009
Frank Warmerdam wrote (31 March 2009):
> OvV_HN wrote:
> > I don't get it. I always thought the existing PROJ (and libproj)
> > function sterea was a full implementation of the double
> > projection, suited for Dutch RD, New Brunswick / Prince Edward
> > stereo and Romanian Stereo 70.
> Well, that is possible. Is someone willing to do some leg work
> confirming if that is the case, and documenting the correct
> of the coordinate systems described in
> for PROJ.4? Some sample test points would also be helpful. Given
> would be happy to update GDAL to support double stereographic and
> some other resources.
I think Oscar is right (at least for the Netherlands,
very likely for the Canadian projections, and I don't
know anything about Romania.)
I found some older posts in the Proj Archives, which
I try to summarize here. (Apologies if there are
errors in my summary.)
Gerald Evenden wrote a post, mainly about the
terminology, but also citing Rueben Schulz, who
> The EPSG does not have any plans to include
> the USGS form in their database since they
> do not know of any coordinate reference systems
> that use it.
Jan Hartmann agreed that the Dutch Stereographic
should be implemented by proj=sterea, not proj=stere,
and attached two images showing
(a) that the United States variant, proj=stere, would
give errors up to 8 meters in the Netherlands, and
(b) that the correct proj=sterea gives errors up
to 0.2 meters, anyway. (?!)
Oscar van Vlijmen replied that proj=sterea should
give errors at most 0.2 millimeters in the Netherlands
(and that's because the Dutch authorities use an
approximative algorithm claimed to have that accuracy,
while proj=sterea is exact (or more exact)).
The up to 0.2 meter error, found by Jan Hartmann,
can be attributed to a grid correction used by
the official transformation tool RDNAPTRANS, writes Oscar.
If I understand him correctly, the official tool conflates
the map projection with a datum shift via grid file.
There are some test points in Oscar's post, but he wrote
> I got with my version of sterea:
so I guess that's his own implementation of sterea,
rather than the implementation in Proj.4.
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