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I'm trying to use ogr2ogr to transform from NAD27 (EPSG:4267) to WGS84 with my custom "towgs84" Bursa-Wolf parameters. However, I think the ogr2ogr uses grids which are part of the GDAL installation and always uses them instead of the towgs84 parameters.

For instance, if I run this gdalsrsinfo command in a projection with testing parameters:

gdalsrsinfo "+proj=longlat +ellps=clrk66 +datum=NAD27 +no_defs +towgs84=1,2,3,0,0,0,0"

I receive this response:

PROJ.4 : '+proj=longlat +ellps=clrk66 +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat +no_defs '

...

So I assume the ogr2ogr avoids the custom parameters and uses nadgrids instead (conus, alaska...) from the share/proj folder.

Do you know, how can I tell ogr2ogr to not use grids? (even though I know they should be more precise)

Or perhaps I can set the path to some other folder?

  • Use +nadgrids=@null. – user30184 Jul 25 '18 at 12:35
  • I've tried that already, but this command: gdalsrsinfo "+proj=longlat +ellps=clrk66 +datum=NAD27 +no_defs +towgs84=1,2,3,0,0,0,0 +nadgrids=@null" Doesn't return towgs parameters on the output: '+proj=longlat +ellps=clrk66 +nadgrids=@null +no_defs ' – Stanislav Dušek Jul 26 '18 at 9:53

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