Hi Marco, Thanks - now that I know that I need to enter the SRID with the "EPSG:" prefix, and that I need to use -1 in the Source Datum transformation I can confirm that it works.
It would be great, if somewhere in the metadata it would be visible that this file is now displayed using the nadgrids/GSB file. Otherwise, I have just to blindly trust, that QGIS does the right thing - which is a bit scary. Do you think it would be possible to add a note in the metadata or general section of the layer properties confirming that QGIS is using a datum transformation to display this file? I will make sure that the documentation will be improved regarding the global settings of the datum transformations. Thanks, Andreas On 2016-10-04 13:17, Marco Hugentobler wrote: > Hi Andi > >> 1. As far as I understand, I have to copy the gsb file to the directory >> where proj stores the gsb files, in my case "C:\Program >> Files\OSGeo4W64\share\proj". Alternatively, one could set another folder >> >and adjust the PROJ_LIB env variable accordingly. > > That should work > > to 2. and 3. : In the option dialog, you enter the datum transformation id of > the datum transformation(s), not the proj parameter. > So to get from epsg:21781 to epsg:2056 with CHENYX06a.gsb, you enter: > > Source crs: EPSG:21781 > Destination crs: EPSG:2056, > Source datum transformation: 100001 > Destination datum transformation: -1 > > An easier way to get to these numbers is to check the box 'Ask for datum > transformations if no default is defined'. Then add a layer in 21781 to the > map and transform it to 2056 on-the-fly. In the dialog asking for the datum > transformation, check 'Remember selection'. The entry will then appear in the > options dialog. > > Regards, > Marco > > On 10/04/16 12:58, Neumann, Andreas wrote: > >> Hi, >> >> I am struggling in QGIS 2x with datum transformations. >> >> The manual is not explicit how to handle this correctly. >> >> Here are the steps I tried: >> >> 1. As far as I understand, I have to copy the gsb file to the directory >> where proj stores the gsb files, in my case "C:\Program >> Files\OSGeo4W64\share\proj". Alternatively, one could set another folder and >> adjust the PROJ_LIB env variable accordingly. >> >> 2. In "Settings" --> "Options" --> "CRS" I can define default datum >> transformations. I tried to enter 21781 (Source CRS), 2056 (Destination >> CRS), +nadgrids=CHENYX06a.gsb (Source datum transfomation). Destionation >> datum has been left empty. >> >> 3. I would expect that whenever this combination 21781 --> 2056 shows up >> that QGIS would ask me to pick one the defaults specified in 2. >> >> The problem is that 2. does not work. When I close the dialogue and reopen >> it, my modifications are gone ... and I never have the chance to select my >> datum transformation option. >> >> Can you help me what I am doing things wrong? >> >> Thank you, >> >> Andreas >> >> _______________________________________________ >> Qgis-user mailing list >> Qgisfirstname.lastname@example.org >> List info: http://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user > > -- > Dr. Marco Hugentobler > Sourcepole - Linux & Open Source Solutions > Weberstrasse 5, CH-8004 Zürich, Switzerland > marco.hugentob...@sourcepole.ch http://www.sourcepole.ch > > _______________________________________________ > Qgis-user mailing list > Qgisemail@example.com > List info: http://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user
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