[Qgis-user] all prj-files broken?

[bernhard.stroebl at jena.de]

Hello Robert,

I reread your former mail and looked at the attached prj files. For my 
area (now EPSG:31468 (Gauss-Krüger, Potsdam, Bessel), future EPSG:25832 
(ETRS89, zone 32)) I experimented with proj4 last year.
I found that the definition of EPSG:25832 in proj4 contains no datum 
information, so datum is "D_unknown". Therefore transforming from 
EPSG:31468 to EPSG:25832 using cs2cs does not perform a datum shift. If 
you parametrize ETRS89 by yourself like this: +proj=tmerc +ellps=GRS80 
+datum=WGS84 ... you get a datum shift and better results.
For Germany you probably may want to use the BeTA2007 grid (see: 
http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/de_dhdn2etrs_beta.php )
Will send you my results (in German) in a personal mail.

regards

Bernhard

Am 15.09.2011 17:45, schrieb Robert Nuske:
> Hi List,
>
> are all prj-files written by QGIS broken or just mine?
>
>
> Saving a layer as shapefile writes always a prj-file with an unkown datum.
>
> That causes problems visualising that shapefile in other GIS and reprojecting
> it  outside of QGIS and. I tested different projected coordinate systems with
> QGIS 1.7 from ubuntugis_unstable on Ubuntu 10.10.
>
>
>
> Example:
> ogrinfo -al -so utm32.shp
> INFO: Open of `utm32.shp'
>        using driver `ESRI Shapefile' successful.
>
> Layer name: utm32
> Geometry: Point
> Feature Count: 3
> Extent: (-3.751456, -2.466990) - (4.628155, 1.957282)
> Layer SRS WKT:
> PROJCS["UTM_Zone_32_Northern_Hemisphere",
>      GEOGCS["GCS_GRS 1980(IUGG, 1980)",
>          DATUM["unknown",
>              SPHEROID["GRS80",6378137,298.257222101]],
>          PRIMEM["Greenwich",0],
>          UNIT["Degree",0.017453292519943295]],
>      PROJECTION["Transverse_Mercator"],
>      PARAMETER["latitude_of_origin",0],
>      PARAMETER["central_meridian",9],
>      PARAMETER["scale_factor",0.9996],
>      PARAMETER["false_easting",500000],
>      PARAMETER["false_northing",0],
>      UNIT["Meter",1]]
> id: Integer (10.0)
>
>
>
> cheers,
>    robert
>
> P.S. I wrote a similar email a week ago, but that one was probably too long.
>
>
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