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<div class="moz-cite-prefix">On 10/09/2012 08:45 PM, Even Rouault
wrote:<br>
</div>
<blockquote
cite="mid:201210092045.01951.even.rouault@mines-paris.org"
type="cite">
Did you check that there was no error or warning reported when
building the VRT ?
</blockquote>
There is no warning from gdalbuiltvrt, is there a flag for a verbose
mode?<br>
<br>
<blockquote
cite="mid:201210092045.01951.even.rouault@mines-paris.org"
type="cite">
What do you mean by "I don't have any data" ? Do you mean that if
you do an extraction from that VRT, you get no significant data ?
</blockquote>
If I make a crop with gdal_translate I only have a hillshade from
the areas originating from SRTM, but not from the Aster areas. The
result of gdal_translate is empty above 61°N. <br>
Obviously this could come from the fact I used to distinct step to
generate hillshade files for SRTM and then for Aster, but I can't
see no differences between them ??<br>
<br>
<blockquote
cite="mid:201210092045.01951.even.rouault@mines-paris.org"
type="cite">What does gdalinfo report on the generated VRT ? Does
it reported extent goes above 60° ? </blockquote>
Should be ok:<br>
<blockquote>Corner Coordinates:<br>
Upper Left (-20037508.316,17822038.826) (180d 0' 0.00"W, 83d 0'
0.50"N)<br>
Lower Left (-20037508.316,-11402298.645) (180d 0' 0.00"W, 71d 0'
0.28"S)<br>
Upper Right (20037428.628,17822038.826) (179d59'57.42"E, 83d 0'
0.50"N)<br>
Lower Right (20037428.628,-11402298.645) (179d59'57.42"E, 71d 0'
0.28"S)<br>
Center ( -39.844, 3209870.091) ( 0d 0' 1.29"W,
27d41'21.83"N)<br>
</blockquote>
<br>
<blockquote
cite="mid:201210092045.01951.even.rouault@mines-paris.org"
type="cite">
<blockquote type="cite">
<pre wrap="">Maybe someone can see a difference between hillshade2_N58E164.tif and
hillshade2_N63E164.tif ? See gdalinfo below, I don't.
</pre>
</blockquote>
<pre wrap="">
I don't see any difference... But all the files you provided in the archive are
definitely odd : their first band is set to 0. Only the 2nd band (alpha band=
has non uniform data. So that might explain what you saw with the huge .vrt</pre>
</blockquote>
This is intended to build a hillshade overlay for webmaps, hence the
black + alpha.<br>
<blockquote
cite="mid:201210092045.01951.even.rouault@mines-paris.org"
type="cite">
<blockquote type="cite">
<pre wrap="">Also, vrt files and some tiles can be found at
<a class="moz-txt-link-freetext" href="http://www.pistes-nordiques.org/download/extract.zip">http://www.pistes-nordiques.org/download/extract.zip</a> (16MB).
</pre>
</blockquote>
<pre wrap="">
No VRT files in that zip.
</pre>
</blockquote>
<a class="moz-txt-link-freetext" href="http://www.pistes-nordiques.org/download/small.vrt">http://www.pistes-nordiques.org/download/small.vrt</a><br>
<a class="moz-txt-link-freetext" href="http://www.pistes-nordiques.org/download/big.vrt">http://www.pistes-nordiques.org/download/big.vrt</a><br>
<br>
Yves<br>
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