On Fri, Mar 23, 2012 at 5:26 AM, <bernhard.stro...@jena.de> wrote: > I just tested with current trunk (compiled on OpenSUSE 64bit): > When I load > PROJCS["Transverse_Mercator",GEOGCS["GCS_bessel",DATUM["D_Deutsches_Hauptdreiecksnetz",SPHEROID["Bessel_1841",6377397.155,299.1528128]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",12],PARAMETER["scale_factor",1],PARAMETER["false_easting",4500000],PARAMETER["false_northing",0],UNIT["Meter",1]] > which is EPSG:31468 (proj4 params in QGIS: +proj=tmerc +lat_0=0 +lon_0=12 > +k=1 +x_0=4500000 +y_0=0 +ellps=bessel > +towgs84=582,105,414,1.04,0.35,-3.08,8.3 +units=m +no_defs) > QGIS creates a user-defined srs: > +proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel > +towgs84=598.1,73.7,418.2,0.202,0.045,-2.455,6.7 +units=m +no_defs > > although there is a difference in towgs84 params the layer matches a > corresponding PostGIS layer defined with EPSG:31468 (I am aware there exist > different towgs84-parameter sets for this datum) > > Same happens when saving as shape file from QGIS deleting the qpj file and > then reloading into QGIS, so QGIS is not able to correctly interpret its own > prj file! > > The only way I found to get the shape file loaded as EPSG:31468 is > appending >>AUTHORITY["EPSG","31468"]<< to the prj file > > PostGIS' spatial_ref_sys table contains the prj string (field srtext) and > the proj4 params (field proj4text) for the projection > srtext: PROJCS["DHDN / 3-degree Gauss-Kruger zone > 4",GEOGCS["DHDN",DATUM["Deutsches_Hauptdreiecksnetz",SPHEROID["Bessel > 1841",6377397.155,299.1528128,AUTHORITY["EPSG","7004"]],AUTHORITY["EPSG","6314"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4314"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",12],PARAMETER["scale_factor",1],PARAMETER["false_easting",4500000],PARAMETER["false_northing",0],AUTHORITY["EPSG","31468"],AXIS["Y",EAST],AXIS["X",NORTH]] > proj4text: +proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 > +ellps=bessel +datum=potsdam +units=m +no_defs > > remarks: > 1) srtext contains >>AUTHORITY["EPSG","31468"]<< > 2) proj4 says >>+datum=potsdam<< whereas srtext says >>>DATUM["Deutsches_Hauptdreiecksnetz"<< > > What could help? > Somehow QGIS needs to use _all_ information given in the prj file and find a > matching srs(proj4 parameters) for that. If there are several matching the > user should choose which to apply, if there is none matching create a > user-defined srs with the parameters given but tell the user. Maybe the > datum parameter should be added to the proj4 definition of the projection. I > am aware that a +datum parameter is only a short for a +towgs84 parameter > but the datum is the same for the projection whereas towgs84 may differ > locally. > > Maybe in at most 5 years' time we won't need GAUSS-KRUEGER any more as we > are supposed to be switched to ETRS89 by then ;-) > > Bernhard > > Am 22.03.2012 19:23, schrieb Etienne Tourigny: > >> The following only applies to builds using master (and upcoming 1.8) >> and gdal-1.9 >> >> Jeff pushed in master the fix which add missing TOWGS84 parameters (by >> using GDAL_FIX_ESRI_WKT=TOWGS84). It is possible that using >> GDAL_FIX_ESRI_WKT=GEOGCS would resolve this issue. Perhaps we couls >> add an option for this, and set the default to GEOGCS? > > > how can I use this?
Berhard, this is already in Master and 1.8. Can you try setting GDAL_FIX_ESRI_WKT=GEOGCS in qgsogrprovider.cpp? You can also play with the command line and see what comes up. GDAL_FIX_ESRI_WKT=GEOGCS gdalsrsinfo file.prj GDAL_FIX_ESRI_WKT=TOWGS84 gdalsrsinfo file.prj GDAL_FIX_ESRI_WKT=NO gdalsrsinfo file.prj although in this case I am afraid that gdal/ogr sees it as Deutsches_Hauptdreiecksnetz all the best, Etienne > >> >> see bug http://hub.qgis.org/issues/5142 >> >> Is there a proper fix for this in 1.7.4? >> >> Etienne >> >> >> On Thu, Mar 22, 2012 at 12:35 PM,<bernhard.stro...@jena.de> wrote: >>> >>> >>> Am 22.03.2012 16:05, schrieb Bernd Vogelgesang: >>> >>>> So, the problem was now described thoroughly, but what are the >>>> conclusions now? >>> >>> >>> >>> There is already a ticket open http://hub.qgis.org/issues/4977 >>> although I have no idea if the issue has been solved or not >>> >>>> >>>> I'm going to spread QGIS in my region in the next months, and it's quite >>>> hard to explain to the people, who to 99% work with EPSG 31468-data, >>>> that they can't ever rely on any data they produce and that they have to >>>> double-check each layer after creation for the right CRS, even if they >>>> set it correctly in each setting available?!? >>>> >>>> I'm not too familiar with all those packages involved handling the CRSs, >>>> so can someone please point me the way who to address with this problem? >>>> >>>> For novice QGIS-users, this "bug" is a real exclusion criterion for QGIS >>>> for they will only create crap with it! >>>> >>>> Again my findings: >>>> Options settings: new layers and projects are created with EPSG 31468, >>>> promting for CRS ist set. >>>> >>>> - EPSG 31468-Layers with a prj-file from ArcGIS get loaded as 2167 >>>> without promting for the CRS >>>> - EPSG 31468-Layers loaded into a EPSG 31468-Region in GRASS are handed >>>> back to QGIS as ... 2167 >>>> - New Layers created in some plugins (like some ftools-plugins), added >>>> to the TOC, are in ... 2167 .. or even 3397 >>>> >>>> >>>> What can i do? (And i really wonder what all those other german users do >>>> and why the don't complain...) >>> >>> >>> >>> For me the base of the problem seems to be that the prj file is not >>> matched >>> to the right EPSG srs. As soon as you tell the layer it is EPSG:31468 it >>> is >>> positioned correctly. So the problem arises only with shapefiles; at my >>> work >>> we use PostGIS for most of our data (that is of course no help for you >>> but >>> explains why I am not "complaining") >>> >>> Bernhard >>>> >>>> >>>> >>>> Thanx for advice >>>> Bernd >>>> >>>> >>>> (QGIS 1.7.4, osgeo4w advanced install, Win7 64bit) >>>> >>>> >>>> > > > ________ Information from NOD32 ________ > This message was checked by NOD32 Antivirus System for Linux Mail Server. > http://www.nod32.com _______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user