<div class="gmail_quote">2011/6/1 Chaitanya kumar CH <span dir="ltr"><<a href="http://chaitanya.ch">chaitanya.ch</a>@<a href="http://gmail.com">gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Giovanni,<br><br>You can use the -et option of gdalwarp. [1]</blockquote><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><br>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.<br>
</blockquote><div><br></div><div>Probably you're right... I will investigate more. Thanks for the hint.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br>[1]: <a href="http://www.gdal.org/gdalwarp.html" target="_blank">http://www.gdal.org/gdalwarp.html</a><br><br><div class="gmail_quote"><div><div></div><div class="h5">On Wed, Jun 1, 2011 at 9:55 PM, G. Allegri <span dir="ltr"><<a href="mailto:giohappy@gmail.com" target="_blank">giohappy@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex"><div><div></div><div class="h5">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.<div>
<br></div><div>My test is against a 21698P x 24647L ArcInfo Binary Grid, with a single band with block dimensions 256x4. Bot SRSs are projected.</div><div>The command is: > gdalwarp -s_srs EPSG:3003 -t_srs EPSG:23032 -et 0.125 hdr.adf test.tiff</div>
<div>It took about 9 minutes to complete.</div><div><br></div><div>Loading the same raster on QGis, which implements its own approximate transformation for on-the-fly reprojection [1], is istantaneous.</div><div>I was wondering if a similar algorithm could be use within Gdal...</div>
<div><br></div><div>Giovanni</div><div><br></div><div>[1] <a href="http://trac.osgeo.org/qgis/browser/trunk/qgis/src/core/qgsrasterprojector.cpp" target="_blank">http://trac.osgeo.org/qgis/browser/trunk/qgis/src/core/qgsrasterprojector.cpp</a></div>
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Chaitanya kumar CH.<br>
/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9494447584<br>17.2416N 80.1426E<br>
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