Hi,
see comments inline:
On Mon, Feb 19, 2018 at 5:23 PM, Alten, Jessica-Aileen <
jessica-aileen.al...@liag-hannover.de> wrote:
> Hi Andrea,
>
> finally I found out what went wrong:
>
> GeoTools picks up the most accurate one from the EPSG database – but in
> this case, the most accurate was not the one which is valid for the whole
> area. You can get an overview on https://epsg.io/31467 3.0 m accuracy
> is for the whole area, 2.0 m accuracy is only valid for the eastern part of
> Germany. Geotools picks the 2.0 m accuracy. As you write, this is a
> consistent behavior and without other parameters it is acceptable and in
> most cases a good choice.
>
> But I found out that the TOWGS84 parameters in the WKT seems to be
> completely ignored, even if I set up the WKT explicitly with these
> parameters in the target CRS. Is this by design - perhaps only for the
> other direction (as the name implies: TO WGS84)?
>
In case the WKT refers to an EPSG database code, the EPSG database still
takes over. GeoServer for example uses a custom setup with 3 factories, a
WKT with low priority (default), the official EPSG database in the middle,
and a custom high priority WKT factory for EPSG database override. Other
software might want to do the same.
See from a user point of view:
http://docs.geoserver.org/latest/en/user/configuration/crshandling/customcrs.html
> Captivated by this topic, I tried another transformation using a grid
> shift file (here: BETA2007.gsb) , because it was described as the most
> accurate one (1 m accuracy). It worked with CRS.findMathTransform(...), but
> finding out where the grid shift file has to be located was a challenge - I
> found the solution in a 5 year old email in a mailing list archive. The gsb
> file resource has to be located in org.geotools.referencing.factory.gridshift!
> I think this should be better documented, perhaps in the FAQ, userguide or
> Javadoc.
>
We are quite thin developer time wise, could you do a pull request updating
the docs yourself? If you have time, it would be much appreciated :-)
GeoServer has a "doc quickfix" guide that can be applied to GeoTools as
well:
http://docs.geoserver.org/latest/en/docguide/quickfix.html
Cheers
Andrea
==
GeoServer Professional Services from the experts! Visit http://goo.gl/it488V
for more information.
==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
Via di Montramito 3/A
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phone: +39 0584 962313
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