Hi Rouault ,<br><br>thx for response.<br><br>>Note that if you want to use more than 2 gigabytes of RAM, you need a 64-bit<br>
>build of GDAL.<br>
<br>I'm use gdal compiled to 64 bit and has 8GB ram, so I can try to use 4GB as cachemax)<br><br>I change my settings and try this configuration:<br><br>gdaladdo -r average -ro --config BIGTIFF_OVERVIEW YES --config GDAL_CACHEMAX 4096 catalog.vrt 4 16 64 256 1024 4096<br>
<br>>I'm also skeptical on the fact that computing such huge overview levels will<br>
>lead to a visually acceptable result. Sometimes you want to use other source of<br>
>data than the high resolution data when displaying low resolution overviews.<br><br>Are you guessing that was better to apply before a gdalwarp to create a new set of starting raster with a lower resolution and only after <br>
calculate the overview from this low resolution set of rasters ?<br><br>Andrea.<br><br><div class="gmail_quote">2012/4/30 Even Rouault <span dir="ltr"><<a href="mailto:even.rouault@mines-paris.org" target="_blank">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><div class="h5"><br>
> Hi,<br>
> I have a huge set of tiffs rasters.<br>
> Any single tiff is a geotiff tiled (256x256) and as an internal overview.<br>
><br>
> To can use this raster dataset to lower scales (full extension) I need to<br>
> create a single simplified tiff raster of all this dataset.<br>
> Now I need to create a single simplified tiff raster .<br>
><br>
> I don't know how is the better way to produce this simplified raster.<br>
> This because the original huge set of rasters are about 2 TB. Every raster<br>
> is about 15000 x 15000 px.<br>
><br>
> SO I start creating a catalog named "cat_fogli.vrt" using gdalbuildvrt.<br>
> And after this was create, I tryed to produce an external overview of this<br>
> catalog.<br>
> using this command:<br>
><br>
> gdaladdo -r average -ro --config BIGTIFF_OVERVIEW YES cat_fogli.vrt 256 512<br>
> 1024 2048 4096<br>
><br>
> Unfortunately gdaladdo seem to be lock. It is take really many time and is<br>
> always on 0%.<br>
><br>
> I don't know if is only a bug time due to the huge size of original raster<br>
> dataset or I'm using the wrong way.<br>
<br>
</div></div>I might not be surprised that it would really take a lot of time. You might want<br>
to increase significatively the block cache to hopefully speed up things. You<br>
can do that by specifying --config GDAL_CACHEMAX some_value_in_megabytes. See<br>
<a href="http://trac.osgeo.org/gdal/wiki/ConfigOptions#GDAL_CACHEMAX" target="_blank">http://trac.osgeo.org/gdal/wiki/ConfigOptions#GDAL_CACHEMAX</a> for more details.<br>
Note that if you want to use more than 2 gigabytes of RAM, you need a 64-bit<br>
build of GDAL.<br>
<br>
Another factor which might explain the slowness is the value of 256 as the first<br>
overview level, which is really a huge value. Computing a block of 256x256 of<br>
that level requires processing 65536x65536 pixels of the base image ! So I would<br>
recommand specifying much lower values before reaching 256. For example 4 16 64.<br>
<br>
I'm also skeptical on the fact that computing such huge overview levels will<br>
lead to a visually acceptable result. Sometimes you want to use other source of<br>
data than the high resolution data when displaying low resolution overviews.<br>
<br>
(Ah, and using gdaltindex will not help for your use case. gdaltindex output is<br>
only used by MapServer AFAIK.)<br>
<br>
Best regards,<br>
<br>
Even<br>
</blockquote></div><br><br clear="all"><br>-- <br>-----------------<br>Andrea Peri<br>. . . . . . . . . <br>qwerty אטלעש<br>-----------------<br><br>