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I am experiencing a small screen space offset when using a WMS layer (origin is GeoServer 2.1.4):

Alignment visualisation

The image shows a red square which is the top left pixel of a tile (GeoTIFF). An exact copy of the same tile is among the tiles in the background provided by my GeoServer. The four images represents the same view (the red square is the same pixel in all four images) just panned a bit inside my QGIS window. The yellow line outlines the corresponding pixel in my WMS layer - added to illustrate the misalignment. I would expect the red square to always align to the yellow line.

Can anyone provide me with some knowledge to why I'm having this misalignment depending on the extent shown on my screen?

I have posted a similar question here proposing that the misalignment could be from a difference in the aspect ratio between the width/height and the bbox in the WMS request. But I'm not sure this is the reason and thus the reason for posting two different questions on the same topic.

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There have been quite a few changes to raster rendering recently in the 'master' branch. Have you tested with the new 1.8 release, or the master branch? –  dakcarto Jun 29 '12 at 2:41
    
Hmm... using QGIS 1.8.0 it still does the same :| –  Chau Jun 29 '12 at 6:49
    
As seen in the images, it is several pixels off. Thus I don't think it is due to the difference in the aspect ratios. –  Chau Jun 29 '12 at 7:59
    
The 1.8.0 release may have the same issues since the new raster changes were committed to master branch shortly after its release. Not sure what platform you are on, but you can either install a nightly build (Linux, Win), or build QGIS from github.com master branch source. –  dakcarto Jun 29 '12 at 18:44
    
At the moment I guess it is GeoServer related. I have posted a question in the GeoServer mailing list, but I haven't recieved any responses though... I get the same problem when manually sending requests directly to GeoServer. –  Chau Jul 2 '12 at 6:45
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