[Qgis-user] Loading big images in QGIS: Erdas img vs. ecw vs. bigtiff

[Andreas Neumann]

Hello,

I would like to discuss the loading of big images in QGIS: I have an
aerial image with 56000 x 44000 pixel. I tried three different approaches.
I wanted to just use one single file instead of tiles. I used gdal to
prepare the images.

Here are my results:

* ECW:
 - compresses fine
 - 500mb limit doesn't seem to apply if I use the -co "LARGE_OK=YES"
 - loads fine and fast with UMN
 - loads very, very long in QGIS: >4 minutes
 - once loaded zooming and panning is very quick

* Erdas imagine (HFA)
 - spill files don't support compression, spill files have to be used if
the filesize is bigger than 2GB
 - loads very fast in QGIS, less than a second
 - once loaded zooming and panning is slower compared with ecw

* bigtiff: couldn't get this to work

So, as a result I would, from a technical point of view, like to go with
ecw, if the initial, very long loading time could be fixed in QGIS.

So, here are my questions:
- will I run into licensing problem with ecw?, esp. if my filesize is
bigger than 500mb?
- can the long loading times of the ecw files be fixed in qgis?
- are there other better alternatives besides ecw/erdas imagine/bigtiff?

Thank you for discussing this issue.

Andreas

-- 
Andreas Neumann
Böschacherstrasse 6, CH-8624 Grüt/Gossau, Switzerland
Email: a.neumann at carto.net, Web:
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