[mapserver-users] Re: QGis 'Zoom to best scale' Not Working

[SixDegrees]

Thank you. I added wms_resx and wms_resy to my mapfile with reasonable values
(and some unreasonable ones, just as tests). This makes no difference. When
I make a GetCapabilities request, the layer's bounding box is correct but it
does NOT contain the resx or resy settings, as I believe it should.

I don't know if this is a problem in my mapfile or in MapServer. My mapfile
layer looks like this (file names changed for proprietary reasons):

LAYER 
   NAME "MyImage"
   GROUP "MyGroup"
   EXTENT 75.80425 35.304 76.01625 35.476
   METADATA 
      "wms_title" "MyImage"
      "wms_group_title" "MyGroup"
      "wms_extent" "75.80425 35.304 76.01625 35.476"
      "wms_srs" "EPSG:4326"
      "wms_resx" "1.0" # Note: these values are for testing only. The actual
values have
      "wms_resy" "1.0" # also been tried, with no success. They are
5.90139233796e-06, -4.85244300668e-06
   END
   PROCESSING "SCALE=AUTO" 
   PROCESSING "SCALE_BUCKETS=256" 
   TYPE RASTER 
   DATA "MyImage.vrt"
   PROJECTION 
      "+proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs"
   END
END




Rahkonen Jukka wrote
> 
> Hi,
> 
> WMS does not advertise by default the native resolution of the data.  I
> have never tried but perhaps adding wms_resx, wms_resy metadata into layer
> metadata would add that information into GetCapabilities
> http://mapserver.org/ogc/wms_server.html.
>  I do not know if QGis can utilise that information even if it exists.
> 
> -Jukka Rahkonen-
> 
> SixDegrees wrote:
> 
>> I'm not sure if this is a QGis problem or a problem with my
> Mapserver-generated WMS layer. When I load a WMS image in QGis, everything
> works as expected except when I select 'Zoom to best scale' I get a
> Mapserver error stating that the bounding box is illegal. And it is - the
> bounding box corner points in the getmap request are identical. This
> selections is supposed to zoom in so the pixels displayed are 1:1 or 100%
> 
>> A look at the capabilities request returned by Mapserver and the mapfile
>> and
> images involved don't show anything obviously wrong. Is it possible that
> QGis is sending the wrong request? Or is something missing from either the
> capabilities document or the mapfile layer?
> 
>> I'm not really sure where to start looking to isolate the problem. Note
>> that
> if I load images directly instead of through Mapserver WMS I am able to
> zoom
> to scale without any problem, which suggests a problem with Mapserver,
> likely in the mapfile. I am using VRT files as intermediaries between the
> Mapfile and the underlying NITF files; it seems that Mapserver should be
> using the affine transform contained in the VRT to determine proper
> scaling,
> but I'm not sure if that is sufficient. Are there arguments that need to
> be
> placed in the Mapfile metadata to help WMS generation along? Or something
> that would cause items in the capabilities document to be left out?
> 
>> Using QGis 1.7.0 on Linux.
> 
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