[Gdal-dev] issue warning to user when performing datum shift (OGR, GDAL)

[Frank Warmerdam]

Dylan Beaudette wrote:
> Hi everyone,
> 
> 
> In light of some recent thought, experimentation, and discussion [1] I
> am wondering if it would be at all possible or even desirable to warn
> the user when a datum shift operation is about to be performed. Within
> the US, and assumming that the NADCON grid was installed with Proj4,
> transforming between NAD27 and NAD83 should work just as expected.
> However, in other parts of the world, this may not be the case.
> Therefore, it might be a good idea to follow the model used in GRASS,
> where the user is specifically prompted for datum transform parameters
> whenever defining a new locatio, in these situations.
> 
> Any thoughts / reasons not to do this?

Dylan,

Well, the most obvious reason not to do it is that the GDAL utilities
are not interactive.  So there is no opportunity to ask.

I think it would be very nice if there was a mechanism to ask stuff
like ogr2ogr to describe what it will do in a transformation but even doing
that would be pretty challenging.

Best regards,
-- 
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