[gdal-dev] How to set GDAL/cs2cs/proj to use NTv2 grid shift file when using EPSG codes?

[Andre Joost]

Am 22.05.2013 20:42, schrieb Thomas Campagne:
> 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",	" nadgrids=@nzgd2kgrid0005.gsb ",
> "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<>
>

I have not yet tested such cases. You might try and report the result 
here ;-)

Greetings,
André Joost