[Proj] [gdal-dev] NTV2 Grid Shift files and gdalwarp

[Jan Hartmann]

Hi Andre,

As far as I know, the transformation from one coordinate system to 
another goes as follow:

- convert source coordinate to latlon
- compute grid shift,  either with +towgs84 parameters or by a grid 
shift raster
- convert resulting latlon to target coordinate

Ntv2 is a Canadian format, where longitudes west of Greenwich are 
positive, and east negative. This is horrible, but that is what things are

So this coordinate is really East. And it works for cs2cs and vector 
data. Could it be that Gdal makes a mistake about this Canadian aspect 
of ntv2?

On 06/25/2013 04:36 PM, Andre Joost wrote:
> Hi Jan,
>
> what strikes me is that
>
>> pj_apply_gridshift(): failed to find a grid shift table for
>> location (6.7638472dW,53.0926086dN)
>
> and
>
>> The source raster has epsg:28992
>
> does not fit together. The first is in Ireland, and EPSG:28992 is 
> valid in the Netherlands. Should it not rather be 6.76 East?
>
> Greetings,
> André Joost
>
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