[Qgis-user] 10 GB Raster Aerial Image in Quantum and POSTGIS

[Alex Mandel]

On 08/27/2013 09:50 AM, Omer Saeed wrote:
> Hello there,
> I have a problem... I have been successful in uploading the raster in
> postgis but when I access it through Qgis. it does not open even after
> several hours.
> 
> I have 10GB aerial image raster and everytime i try to open it through QGIS
> it does not open even after many hours and QGIS crashes...
> 
> why is this happening...?? is it really due to the file size..??
> 
> Regards,
> Omer.
> 

Large rasters should not be loaded all at once in Postgis because it
will shove the whole image into a single row. You have to make sure to
using the Tiling option to split it into more efficient chunks
http://postgis.net/docs/using_raster.xml.html#RT_Raster_Loader

Assuming you did that (which you probably did because 10GB sounds too
large for 1 row anyways), then the next issue is that postgis while it
supports rasters is still quite slow on many raster operations,
apparently gdal read of such data is also new and not as fast as it
could be.
http://gis.stackexchange.com/questions/32535/how-to-speed-up-postgis-raster-layer-display-in-qgis

So yes it's entirely possible that it's simply due to the size of the
file. 10 GB is a larger than average single file, especially without the
use of overviews common in image formats.

Thanks,
Alex