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

Rahkonen Jukka Jukka.Rahkonen at mmmtike.fi
Mon Nov 21 15:43:51 EST 2011


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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