[Gdal-dev] gdal warp code silently skipping datum shift

[Frank Warmerdam]

Brent Fraser wrote:
> Frank,
> 
>   I'd love to see a message (from proj? gdal?) to indicate which method (and
> which grid file if applicable) the tool was using to resolve the difference
> in datums.  It would take away a lot of the worry when using proj/gdal to do
> datum conversions based on NTv2, etc.

Brent,

I hadn't actually contemplated reporting which grid shift file is used.
In fact, in a single call to pj_transform(), it is possible for multiple
grid shift files to get used depending on where the points happen to fall.

But we could at least report which PROJ.4 clauses (towgs84 or nadgrids)
is being used for the source and destination coordinate system.  Perhaps
PROJ.4 could be extended with a function to report the mechanisms used
for a give sample point.  This would be a fair amount of work though.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGF, http://osgeo.org