[gdal-dev] gdal warp with approximate transformation seems a bit slow...

[Chaitanya kumar CH]

Giovanni,

You can use the -et option of gdalwarp. [1]

Are you sure qgis is warping the whole image and not just the scaled down
version of the original? Processing a half giga pixel image ought to be
longer than instantaneous.

[1]: http://www.gdal.org/gdalwarp.html

On Wed, Jun 1, 2011 at 9:55 PM, G. Allegri <giohappy at gmail.com> wrote:

> I was doing some tests on Gvsig for raster reprojection, where gdal warp is
> used. Gvsig uses a default error threshold of 0.125, which AFAIK makes gdal
> warp fall back to an approximate transformation. Anyway the reprojection is
> quite slow, even if significantly faster then GDALGenImgProjTransform.
>
> My test is against a 21698P x 24647L ArcInfo Binary Grid, with a single
> band with block dimensions 256x4. Bot SRSs are projected.
> The command is: > gdalwarp -s_srs EPSG:3003 -t_srs EPSG:23032 -et 0.125
> hdr.adf test.tiff
> It took about 9 minutes to complete.
>
> Loading the same raster on QGis, which implements its own approximate
> transformation for on-the-fly reprojection [1], is istantaneous.
> I was wondering if a similar algorithm could be use within Gdal...
>
> Giovanni
>
> [1]
> http://trac.osgeo.org/qgis/browser/trunk/qgis/src/core/qgsrasterprojector.cpp
>
>
>
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>



-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
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