Andre Joost wrote > Am 29.11.2013 09:59, schrieb Jeremy Palmer: >> Hi gdal-devs, >> >> I'm trying to shift shapefile data using a custom NTv2 grid file. The >> logical source and destination coordinate systems are the same >> (geographic coordinates EPSG:4167), I only want to shift the data. >> >> The type of command I'm trying to run is: >> >> ogr2ogr -f "Esri Shapefile" -a_srs "+proj=longlat +ellps=GRS80" >> -t_srs "+proj=longlat +ellps=GRS80 +nadgrids=custom_grid.gsb +wktext" >> dst_datasource_name src_datasource_name >> >> but the output shapefile does not get transformed... >> >> Is this because there is a short circuit in proj4 if the ellipsoids >> are the same? >> > > No, you have to explicitely specify +towgs84=0,0,0,0,0,0,0 for the first > srs. Otherwise it is assumed that both share the same datum. > > HTH, > André Joost > > _______________________________________________ > gdal-dev mailing list
> [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev Andre is on the right track. But, I believe you need to specify the +nadgrids=c:\custom_grid.gsb in your source projection, then use the +towgs84=0,0,0,0,0,0,0 in your target. You may get away without specifying any path to your gsb, not sure. HTH Regards, Steve -- View this message in context: http://osgeo-org.1560.x6.nabble.com/gdal-dev-Force-application-of-ntv2-grid-tp5091818p5093536.html Sent from the GDAL - Dev mailing list archive at Nabble.com. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
