<br><br><div class="gmail_quote">2012/2/2 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 Andrea Peri <<a href="mailto:aperi2007@gmail.com">aperi2007@gmail.com</a>>:<br>
<div class="im"><br>
> Hi,<br>
><br>
> Unfortunately I was unable to test with GDB.<br>
> My skill was not enough :(<br>
<br>
</div>Well, provided you have gdb installed, it is "just" a matter of :<br>
<br>
1) "gdb qgis"<br>
2) in the gdb console, type "run" and validate<br>
3) when qgis is slow, switch to the console with gdb and hit Ctrl+C<br>
4) in the gdb console, type "bt" (for backtrace)and validate, and then it can<br>
give some interesting information<br>
5) to go on qgis execution, type "c" (continue) and validate<br>
6) you can go to 3) again<br>
<div class="im"><br></div></blockquote><div><br>thx, I try it .<br> <br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="im">
><br>
> However I try other ways</div></blockquote><div>> <br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="im">.....</div></blockquote>
<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 class="im">> So qgis necessary must open all the raster to understand what raster is on<br>
> the visible portion on the canvas.<br>
<br>
</div>No, what you show above is sufficient to defer the loading of individual tiles,<br>
until they are really necessary.<br>
<br>
What I suspect is that your vrt has no associated overviews, so when you open<br>
qgis, it will try to display the overall coverage of the raster, which then will<br>
require to open each tile.<br>
<br>
Try "gdaladdo your.vrt 2 4 8 16 32"<br>
<div class="im"><br></div></blockquote><div><br>I try to create the overview, but it is really sloow .<br>After 1hours is to 0%. <br><br>I will try with a selection of few rasters.<br><br><br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div class="im">
><br>
> I guess this is a good reason to explain because it is so slow when in the<br>
> catalog there and many hundred of rasters.<br>
><br>
> Unfortunately I don't find any option in gdalbuildvrt to add the extension<br>
> of every raster in the catalog.<br>
<br>
</div>There's none : the above information that is generated by default is sufficient.<br>
<br></blockquote><div><br>Sorry Roualt,<br>the catalog give the start point and the number of pixel , but miss the size in meters or "unit of map" of every pixel so for me was not possible to detect the bbox of every raster.<br>
Perhaps in the overview there is the missing information ?<br><br>>Best regards,<br>
><br>>Even<br>
</div></div><br>Thx,<br>Andrea.<br><br clear="all"><br>-- <br>-----------------<br>Andrea Peri<br>. . . . . . . . . <br>qwerty אטלעש<br>-----------------<br><br>