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

[G. Allegri]

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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