That's some great debugging Jukka! Philippe - seems like a valid issue. Would you be able to open an issue with these details? Including the workaround as this could be a hard issue to fix/test, so it may be open a while.
Seth On Fri, Feb 27, 2026, at 5:58 PM, Philippe Ghesquiere via MapServer-users wrote: > Hi Jukka, > > Thanks for your clear, in depth explanation. > Your "OVERSAMPLE_RATIO=1.0" workaround works just fine. And it makes sense to > me. > > Philippe > > On Fri, Feb 27, 2026 at 3:27 PM Rahkonen Jukka > <[email protected]> wrote: >> Hi, >> >> Thank you for the test package. I think I know what happens and I have a fix >> or a workaround for you. >> >> I added some more debugging first, not sure if all these were really needed. >> >> CONFIG MS_ERRORFILE "c:\ms4w_data\test2\errorfile.txt" >> CONFIG "CPL_DEBUG" "ON" >> CONFIG "PROJ_DEBUG" "ON" >> >> The MS_ERRORFILE shows what is the difference. >> >> >> WMS 1.1.0 is using method "msDrawRasterLayerGDAL()" >> >> msDrawRasterLayerGDAL(): Entering transform. >> msDrawRasterLayerGDAL(): src=0,0,4096,2048, dst=0,10,994,498 >> >> WMS 1.3.0 probably believes that is must do warping and it selects to use >> method "msDrawGDAL(Image_Layer)" >> >> msResampleGDALToMap in effect: cellsize = 0.181087 >> msDrawGDAL(Image_Layer): using RAW_WINDOW=0 0 4096 2048, dst=0,0,1988,994 >> >> I do not understand the details, but in WMS 1.3.0 case the values in "dst" >> (destination) are about doubled. >> >> The Apache error log shows that depending on the WMS version, GDAL selects >> different overview levels from the GeoPackage, either "overview 1024 x 512" >> or "overview 2048 x 1024" >> >> Maybe the best fix for this case would be to make Mapserver consider that >> EPSG:4326 and CRS:84 are the same and no warping is needed between those >> two. And therefore there is no need to select the other code path. >> >> As a workaround, see https://mapserver.org/input/raster.html and add this >> line into your LAYER: >> PROCESSING "OVERSAMPLE_RATIO=1.0" >> Oversampling means that higher resolution data than what is needed for the >> output is read in for warping. That improves the quality of the warped >> result. That is fine for orthophotos and scanned maps, but in your use case >> the better resolution overview contains also different data from another >> zoom level. >> >> I tried also "PROCESSING ALLOW_OVERSAMPLE=NO" but for some reason it did not >> work for me. I was testing with a bit old MapServer version 8.3.0-dev (MS4W >> 5.0.0). >> >> -Jukka Rahkonen- > The information in this e-mail is confidential. The contents may not be > disclosed or used by anyone other than the addressee. Access to this e-mail > by anyone else is unauthorised. > If you are not the intended recipient, please notify Airbus immediately and > delete this e-mail. > Airbus cannot accept any responsibility for the accuracy or completeness of > this e-mail as it has been sent over public networks. If you have any > concerns over the content of this message or its Accuracy or Integrity, > please contact Airbus immediately. > All outgoing e-mails from Airbus are checked using regularly updated virus > scanning software but you should take whatever measures you deem to be > appropriate to ensure that this message and any attachments are virus free. > _______________________________________________ > MapServer-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/mapserver-users >
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