The problem was simpler then it appeared: I didn't realize that QGIS output is Float64. Yet I don't know why QGIS chosed to use this data type...
giovanni 2014-07-05 17:56 GMT+02:00 Even Rouault <[email protected]>: > Le samedi 05 juillet 2014 17:25:48, G. Allegri a écrit : > > > QGIS is usually just calls to gdal, which makes this even more > > > mysterious. > > > > Yes, in the end it uses gdal, but it chooses the way blocks are read and > > written. > > If I remember correctly geotiff final sizes may depend on block ordering > > and memory alignment. > > In that instance, the target geotiff has a natural block dimension which > is a > raster line. > If QGIS writes the geotiff by 256x256 blocks (this is just a guess. I've > not > verified), the same raster line will be written several times. As it is a > compressed geotiff, the resulting raster line will be each time being > bigger > since the initial zeros will be replaced by actual values. And if the new > size > of the line is bigger than its previous size, the new line will be > rewritten > at the end of the file, losing the space previously occupied. > > > Maybe this is the case, QGIS raster provider not doing the best at this > > level? Don't know, but this discussion is for the QGIS ml ;) > > > > giovanni > > > > > On 7/5/2014 9:09 AM, G. Allegri wrote: > > > > I agree with you David, I'm surprised too. > > > > Anyway, gdal_translate is run without compression options. > > > > I've written to the QGIS devs (it was the software) to verify what's > > > > happening with its raster file writer code... > > -- > Geospatial professional services > http://even.rouault.free.fr/services.html > -- Giovanni Allegri http://about.me/giovanniallegri Twitter: https://twitter.com/_giohappy_ blog: http://blog.spaziogis.it GEO+ geomatica in Italia http://bit.ly/GEOplus
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