[Qgis-user] wrong scale printing with qgis web client

[Tom Palan]

hi,

included you find my patch...It is very specific to my application (using EPSG:31225 austrian projection, and a reference point in the middle of Austria).
I works like this:

- I choose a point of reference (in EPSG:31255), and add the width and height of the needed print bounding-box as a second point.
- then I project both points into EPSG:3857 (using the proj4-library), and subtract these 2 points to get the widht and height of the resulting bounding-box.

I have to admin I do not know enough about projections to judge if this could be made simpler...I think this is just symptom-control, there must be a better solution to this.

Another downside: I have to use the debug-version of GeoExt and not the single file version.

Tom

On Thu, Dec 03, 2015 at 12:34:53PM +0100, Enrico Ferreguti wrote:
> Well, I made some checks....
> I verified that, using osm backgound layers, all projects were reprojected
> to epsg:3857 from epsg:3003.
> Setting (in GlobalOptions.js) all background layer to false and authid
> accordingly with project authid (epsg:3003) I verified that I get now right
> scaled maps (the right scaled pdf is attached).
> Then I confirm that the wrong behaviour (as from Tom email)
> 
> >  happens when projection is set to EPSG3857 for using
> > Google,OSM,...basemaps, and your data is in another projection.
> >
> 
> Qgis server version is 2.10 running under ubuntu.
> 
> I would suggest Tom to share GeoExt patch!
> 
> Regards.
> 
> 2015-12-02 12:20 GMT+01:00 Bernhard Ströbl <bernhard.stroebl at jena.de>:
> 
> > Hi Enrico,
> >
> > the scalebar on the pdf obviously does not fit the numerical scale.
> > Questions:
> > 1) First we have to determine, if a) the numerical scale is wrong but the
> > scalebar is correct or b) vice versa. What happens if you print out the
> > same Layout in the same project from QGIS desktop in scale 1:1000? Does the
> > scalebar fit the numerical scale? Is the displayed map extent the same?
> > 2) What projection(s) do you use?
> > 3) Which version of QGIS server are you running?
> >
> > Bernhard
> >
> >
> > Am 02.12.2015 um 11:54 schrieb Enrico Ferreguti:
> >
> >> Hi,
> >> I'm getting prints with wrong scale from qgis web client.
> >> Apparently everything is fine, I select the layout, the scale from the
> >> select box, I place the bounding box in the map and then I print. The
> >> layout contains a numeric scalebar that correclty reports the selected
> >> scale but if I manually measure on paper the printed image appears that
> >> the map has a wrong scale by a 1.43x factor
> >>
> >> I verified the behaviour with different projects and projections on
> >> various servers.
> >>
> >> Should I open a ticket or Am I doing something wrong?
> >>
> >> Attached there is a print with wrong graphical and numeric scalebars.
> >> The location is the following:
> >> http://www.openstreetmap.org/#map=19/45.3963826129/11.8795777003
> >>
> >> Regards.
> >> Enrico Ferreguti
> >>
> >>
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> >
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-- 
Tom Palan
palan3 IT solutions OG
Grillenbergstr. 4
A-4407 Dietach
Tel.: +43 (0) 680 3280940
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