[gdal-dev] "fixing" CRS for a read-only raster

[Even Rouault]

Idan,

> 
> I have an ECW raster with a wrong CRS (which I believe can't change because
> I don't have the ECW writer license).

Changes in the header don't require a write license

So gdal_edit.py -a_srs EPSG:xxxx your.ecw

should work and modify in place the ECW

Otherwise you can add the -ro flag to the above, and it will generate a 
.ecw.aux.xml file with the overriden projection info.

> Is there an option to add an aux/prj file next to it so that GDAL will read
> the correct CRS from the aux file instead of from the ECW file ( i.e. from
> GeoServer/QGIS) ?
> I know I can workaround it with a VRT file but I think it might degrade the
> performance.

For "simple VRT" generated with "gdal_translate your.ecw your.vrt -a_srs 
EPSG:xxxx -of VRT", the VRT driver has optimizations to directly forward pixel 
requests to the underlying driver with minimal overhead.

Even

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