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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