02.02.2012 18:10, Andrea Peri ?????:
2012/2/2 Even Rouault <even.roua...@mines-paris.org
<mailto:even.roua...@mines-paris.org>>
Selon Andrea Peri <aperi2...@gmail.com <mailto:aperi2...@gmail.com>>:
> Hi,
>
> Unfortunately I was unable to test with GDB.
> My skill was not enough :(
Well, provided you have gdb installed, it is "just" a matter of :
1) "gdb qgis"
2) in the gdb console, type "run" and validate
3) when qgis is slow, switch to the console with gdb and hit Ctrl+C
4) in the gdb console, type "bt" (for backtrace)and validate, and
then it can
give some interesting information
5) to go on qgis execution, type "c" (continue) and validate
6) you can go to 3) again
thx, I try it .
>
> However I try other ways
>
.....
> So qgis necessary must open all the raster to understand what
raster is on
> the visible portion on the canvas.
No, what you show above is sufficient to defer the loading of
individual tiles,
until they are really necessary.
What I suspect is that your vrt has no associated overviews, so
when you open
qgis, it will try to display the overall coverage of the raster,
which then will
require to open each tile.
Try "gdaladdo your.vrt 2 4 8 16 32"
I try to create the overview, but it is really sloow .
After 1hours is to 0%.
I will try with a selection of few rasters.
>
> I guess this is a good reason to explain because it is so slow
when in the
> catalog there and many hundred of rasters.
>
> Unfortunately I don't find any option in gdalbuildvrt to add the
extension
> of every raster in the catalog.
There's none : the above information that is generated by default
is sufficient.
Sorry Roualt,
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.
Perhaps in the overview there is the missing information ?
>Best regards,
>
>Even
Thx,
Andrea.
--
-----------------
Andrea Peri
. . . . . . . . .
qwerty àèìòù
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We have discussed this problem with Even. I'll fix it. The work is in
process.
Best regards,
Dmitry
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