[gdal-dev] Relation between PROJ8, GDAL, and national grids

[Even Rouault]

Juan Pedro,


>
> I'm at a loss trying to understand the relationship between PROJ8, 
> GDAL, and how to use TIFF national grids. So far my findings are:
>
> - PROJ8 is installed and cs2cs uses the grid to transform, performing 
> an extremely accurate shift;
>
> - GDAL, compile on the above PROJ8, when using
> gdaltransform, yields less accurate

There's no fundamental reason for transforms with gdaltransform being 
less accurate than with cs2cs. You have to be much more specific with 
the exact gdaltransform invokation you are trying. And are you really 
sure that you use the PROJ version you think ? (check with ldd 
libgdal.so on Linux)

You can also set the PROJ_DEBUG=2 and CPL_DEBUG=ON environment variables 
and look at the traces.

Even


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