[QGIS-trac] Re: [Quantum GIS] #3753: "Zoom to best scale" takes a long time (inf?) for TMS layers.

[Quantum GIS]

#3753: "Zoom to best scale" takes a long time (inf?) for TMS layers.
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        Reporter:  borysiasty                                 |         Owner:  rblazek                                 
            Type:  bug                                        |        Status:  closed                                  
        Priority:  critical: causes crash or data corruption  |     Milestone:  Version 1.7.0                           
       Component:  Rasters                                    |       Version:  Trunk                                   
      Resolution:  invalid                                    |      Keywords:  raster provider, TMS, zoom to best scale
Platform_version:                                             |      Platform:  Debian                                  
        Must_fix:  No                                         |   Status_info:  0                                       
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Changes (by borysiasty):

  * status:  new => closed
  * resolution:  => invalid


Comment:

 Ok, I've checked it twice and the ticket was invalid. Sorry. The problem
 was in the xml file.

 The "zoom to best scale" zooms to the zoom level defined in the
 <TileLevel> tag in the xml file. It was set to 19, while the OSM TMS
 supports zoom levels up to 18. If you set that tag to 18, everything works
 ok.

 About the "synchronization". The OpenLayers layer, as well as WMS-C one,
 fixes the scale series to available zoom levels, so it works OOTB and it's
 fine. With the gdal minidriver, the scale is contnous, so the user has to
 take care of it and keep it always 1:2257, 1:4514, 1:9028 etc. Otherwise
 the image is ugly rescaled. There simplest way to keep the scale always
 corresponding to the avilable zoom levels is to use the "zoom to best
 scale" and then only use "zoom in" and "zoom out" to keep the 2x factor. I
 hope I'm clear this time :)

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Ticket URL: <http://trac.osgeo.org/qgis/ticket/3753#comment:2>
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