Hi,<br><br>Unfortunately I was unable to test with GDB.<br>My skill was not enough :(<br><br>However I try other ways.<br><br>I will use a utility to test the disk activity and after put the qgis canvas on a little portion of land covered I add the catalog.vrt.<br>
Using this utility I can see that qggis try to open all the raster instead of open only the single raster necessary to visualize the portion of land in the canvas.<br><br>After this I see the xml in the catalog:<br><br><SimpleSource><br>
<SourceFilename relativeToVRT="0">F:\....\216110_2010.ecw</SourceFilename><br> <SourceBand>1</SourceBand><br> <SourceProperties RasterXSize="13900" RasterYSize="11760" DataType="Byte" BlockXSize="13900" BlockYSize="1" /><br>
<SrcRect xOff="0" yOff="0" xSize="13900" ySize="11760" /><br> <DstRect xOff="26320" yOff="140" xSize="13900" ySize="11760" /><br>
</SimpleSource><br><br>And I notice also that the catalog don't store on every tag of a raster the single bbox of that raster.<br>So qgis necessary must open all the raster to understand what raster is on the visible portion on the canvas.<br>
<br>I guess this is a good reason to explain because it is so slow when in the catalog there and many hundred of rasters.<br><br>Unfortunately I don't find any option in gdalbuildvrt to add the extension of every raster in the catalog.<br>
<br>Andrea.<br><br><div class="gmail_quote">2012/1/31 Even Rouault <span dir="ltr"><<a href="mailto:even.rouault@mines-paris.org">even.rouault@mines-paris.org</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Selon Dmitry Baryshnikov <<a href="mailto:polimax@mail.ru">polimax@mail.ru</a>>:<br>
<br>
> 31.01.2012 16:54, Andrea Peri ?????:<br>
<div class="im">> > Hi,<br>
> > using qgis I notice that it is more slow to open some raster from a<br>
> > catalog.vrt rather than opening the same raster directly.<br>
> > The slow is so big that when the catalog has many raster qgis take<br>
> > many time to open the catalog.<br>
> ><br>
> > Because qgis use gdal to read raster and also to read a catalog.<br>
> > I guess this is not an issue for qgis. But is a question of gdal.<br>
> ><br>
> > Before to start to do some test I like to know if there is some know<br>
> > issue on this.<br>
<br>
</div>> I think this bug are mentioned in such tickets<br>
> <a href="http://trac.osgeo.org/gdal/ticket/2076" target="_blank">http://trac.osgeo.org/gdal/ticket/2076</a> and<br>
> <a href="http://trac.osgeo.org/gdal/ticket/3482" target="_blank">http://trac.osgeo.org/gdal/ticket/3482</a><br>
> QGIS more slow because it warp image (if it from VRT or have some<br>
> rotation in meta and etc.) and have no overviews. You can see if image<br>
> is warped in layer properties metadata tab -> driver.<br>
<br>
Yes that's one possibility. A more pragmatic way would be to run qgis under<br>
GDB/DDD, and when it is stuck, Ctrl+C to see in which GDAL function it is<br>
stuck... That should give some hints.<br>
<br>
><br>
> Best regards,<br>
> Dmitry<br>
><br>
<br>
<br>
</blockquote></div><br><br clear="all"><br>-- <br>-----------------<br>Andrea Peri<br>. . . . . . . . . <br>qwerty àèìòù<br>-----------------<br><br>