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<div class="moz-cite-prefix">Hi Paolo,<br>
the te option set the output raster size, not the subraster. You
have to use gdal_translate to get subraster and then use gdalwarp.
<br>
Also <b style="color: rgb(0, 0, 0); font-family: 'Lucida Grande',
Verdana, Geneva, Arial, sans-serif; font-size: 12px; font-style:
normal; font-variant: normal; letter-spacing: normal;
line-height: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space: normal;
widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255);">multi option is
preferable to multi threaded execution. <br>
</b>
<pre class="moz-signature" cols="72">Best regards,
Dmitry</pre>
24.12.2013 21:48, Paolo Corti пишет:<br>
</div>
<blockquote
cite="mid:CAHXrU-+6DgriN-Aki13DkLYu+DN3aOxMGbbyrtvT+DagUkbg2Q@mail.gmail.com"
type="cite">
<p dir="ltr">Hi all</p>
<p dir="ltr">I am experiencing problems using a VRT dataset built
from a large directory of .tif files.</p>
<p dir="ltr">While if a build the VRT from just one of these
datasets, gdalwarp will work very fast with it, if I use the VRT
will all of these images, it becomes undefinite times slower.</p>
<p dir="ltr">Debugging the gdalwarp command, it seems that
gdalwarp accesses every single raster composing the vrt
datasource, even if that single raster is not within the extent
defined by the -te gdalwarp option.</p>
<p dir="ltr">Here is the output for a vrt composed by just one
single .tif file:</p>
<p dir="ltr">$ time gdalwarp -te -88.88 20.28 -87.88 21.28
single.vrt single.tiff<br>
...<br>
Src=1344,4463,1201x1201 Dst=0,0,1200x1200<br>
0...10...20...30...40...50...60...70...80...90...100 - done.<br>
GDAL: GDALClose(single.vrt, this=0x8ca6ef8)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif,
this=0x8ca9aa8)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif,
this=0x8ca7208)<br>
GDAL: GDALClose(single.tiff, this=0x8ca7e98)<br>
GDAL: In GDALDestroy - unloading GDAL shared library.</p>
<p dir="ltr">real 0m0.137s<br>
user 0m0.076s<br>
sys 0m0.052s</p>
<p dir="ltr">and here is the output for a vrt composed of all of
the .tif files:</p>
<p dir="ltr">capooti@ubuntu:~/training/vrt$ time gdalwarp -te
-88.88 20.28 -87.88 21.28 all.vrt all.tiff<br>
...<br>
Src=7344,16464,1201x1201 Dst=0,0,1200x1200<br>
0...10...20...30...40...50...60...70...80...90...100 - done.<br>
GDAL: GDALClose(all.vrt, this=0x9d332b0)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_18_09.tif,
this=0x9d46618)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif,
this=0x9d467c8)<br>
...<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_35_09.tif,
this=0x9d4c1b8)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_35_10.tif,
this=0x9d4c3a8)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif,
this=0x9d30800)<br>
GDAL: GDALClose(/home/capooti/training/vrt/srtm_35_11.tif,
this=0x9d4c630)<br>
GDAL: GDALClose(all.tiff, this=0x9d33990)<br>
GDAL: In GDALDestroy - unloading GDAL shared library.</p>
<p dir="ltr">real 61m12.130s<br>
user 0m6.076s<br>
sys 0m18.052s</p>
<p dir="ltr">Any hint here to prevent gdalwarp to access the
unneeded source raster files - the defined extent in -te should
just hit a couple of ones?<br>
thanks in advance<br>
p</p>
<p dir="ltr">-- <br>
Paolo Corti<br>
Geospatial software developer<br>
web: <a moz-do-not-send="true" href="http://www.paolocorti.net">http://www.paolocorti.net</a><br>
twitter: @capooti<br>
skype: capooti</p>
<br>
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</blockquote>
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