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

[SixDegrees]

Sorry, I was wrong in the previous message; the resx and resy settings do
show up in the capabilities document. They make no difference, however; the
bounding box requested by QGis is still in error.


SixDegrees wrote
> 
> 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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> 


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