Thanks André! I will add a line for AGD66 datum and nadgrid file in pj_datums.c, and make the appropriate change in the epsg file , and compile from source.
Is possible to default to the use of +towgs84 when there is no successful grids with +nadgrids? For New-Zealand the line in pj_datums.c is: "nzgd49", "nadgrids=nzgd2kgrid0005.gsb", "intl", "New Zealand Geodetic Datum 1949" And the epsg file contains: # NZGD49 <4272> +proj=longlat +datum=nzgd49 +no_defs <> Could the following work if points are not located within the area covered by the NTv2 file? pj_datums.c contains: "nzgd49", " [email protected] ", "intl", "New Zealand Geodetic Datum 1949" And the epsg file contains: # NZGD49 <4272> +proj=longlat +datum=nzgd49 + towgs84=59.47,-5.04,187.44,0.47,-0.1,1.024,-4.5993 +no_defs <> -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andre Joost Sent: May-17-13 10:21 AM To: [email protected] Subject: Re: [gdal-dev] How to set GDAL/cs2cs/proj to use NTv2 grid shift file when using EPSG codes? Am 17.05.2013 19:00, schrieb Thomas Campagne: > When I run cs2cs -v +init=epsg:4267 I still do not understand how the > +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat parameter is being > generated as I cannot find it within the text/csv files. > EPSG:4267 expands to +proj=longlat +datum=NAD27 +no_defs and the nadgrids are in the "+datum=NAD27". This is hardcoded in <http://trac.osgeo.org/proj/browser/trunk/proj/src/pj_datums.c> > "NAD27", "nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat", > "clrk66", > "North_American_Datum_1927", > Any idea about which files to edit to add the nadgrids parameter to > the proj string referenced by a given EPSG code (4202 for AGD66 as > example)? You could add a line for AGD66 datum and nadgrid file in the file, and compile from source. And you have to change the share/proj/epsg file to use your datum istead of +towgs84. Or try to insert the +nadgrids=<filename> for the AGD66 entry directly. HTH, André Joost _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
