[Gdal-dev] Grid based transformation with ogr2ogr

[Matt Wilkie]

Hi Uwe,Frank,

>> as a solution for the upcoming datum shift in Germany (from DHDN to
>>  ETRS89[=WGS84]) I'm currently experimenting with grid based datum 
>> shifts.
...
> Unfortunately gdalwarp uses OGC Well Known Text as the internal 
> coordinate system representation and that does not include any 
> support for grid files. NAD27/NAD83 grid shift files are handled as a
> special case.
> 
> So the PROJ.4 representation is parsed and converted to WKT, and then
>  converted back to PROJ.4 format to do the actual coordinate
> transformation. But by then the grid list is lost.
> 
> Unfortunately, there is no current way to accomplish what you want 
> with gdalwarp.  I would encourage you to file a bug report.  I think 
> I may make an non-standard extension or two to WKT to allow 
> transporting some of these values I need for PROJ.4.


To my eye this looks related to my earlier proposal to develop an ogr
module to apply the Canadian Correction Matrices (CORMAT) to vector 
data. Is that correct? If these are similar problems perhaps there is an 
opportunity to share resources.

cheers,

-- 
matt wilkie
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