[gdal-dev] On-the-fly reprojection using the OGR VRT driver?

Even Rouault even.rouault at mines-paris.org
Thu Dec 22 08:27:44 EST 2011


Selon Homme Zwaagstra <hrz at geodata.soton.ac.uk>:

> Hello,
>
> I'm interested in performing on-the-fly coordinate transformations of
> OGR data sources using the Virtual Format (VRT) driver. That is,
> producing a file that is the vector equivalent of:
>
> gdalwarp -of VRT -t_srs "+init=epsg:4326" input.tif transformed.vrt
>
> I understand ogr2ogr cannot do this but am wondering if the vector
> version of `transformed.vrt` can be created manually?

Yes, ogr2ogr -f VRT is not implemented as such. But there's a python script in
http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/ogr2vrt.py that can
generate a VRT schema from a OGR datasource

>
> Having looked at the source code it looks like the answer will be no
> ;) - if this is the case is there be a reason not to file an
> enhancement request for this functionality?

But indeed, the OGR VRT format doesn't currently support on-the-fly
reprojection. This could certainly be implemented. I somehow remember to have
worked on a prototype for this. The tricky part was the interaction with spatial
filter or spatial extent where you must apply the reverse reprojection to the
source layer.




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