[Qgis-user] Scale seems strange in

Wed Nov 2 03:47:37 PDT 2011

James

I am using QGIS-Trunk under ubuntu 10.04. The canvas projection is set
to 27700 and Layer unit to metre.

The scale seems to be fine and not affected by panning.

Cheers
Saber

On Wed, 2011-11-02 at 10:43 +0000, James Stott wrote:
> An update:
> 
>  
> 
> This is also happening on a colleague’s machine. I have reverted back
> to the previous OSGeo4W nightly and that doesn’t fix the problem.
> Uninstalling and reinstalling doesn’t work.
> 
>  
> 
> In 1.7, if I open up this certain dataset of viewpoint locations, it
> opens with a scale of 1:53478. In 1.8 if I load the dataset it opens
> at a scale of 1:5325654358. If I use the pan tool and just click on
> the map the scale changes to 1:631588609, then 1:2918610855, then
> 1:2934133484 and so on. Distance measures seem unaffected. It seems to
> be being caused by the units of the project being set to degrees. I
> have saved a project and the units are set to degrees. If I open an
> old project up it opens at the correct scale. In my old project files
> it is set to metres. (see examples below). It seems I have to make
> sure Enable on the fly projection is unticked in the project
> properties, and then manually set the Layer units to metres in the
> general tab.
> 
>  
> 
> I was also having problems a while ago with exporting to MapInfo but I
> have just tried this and it works. See links below for details. It is
> including the 79 not the 104 now.
> 
>  
> 
> http://gis.stackexchange.com/questions/14350/qgis-and-mapinfo-projections-epsg-27700-british-national-grid
> 
> http://hub.qgis.org/issues/4271
> 
>  
> 
> New project:
> 
>  
> 
> <mapcanvas>
> 
>         <units>degrees</units>
> 
>         <extent>
> 
>             <xmin>384571.226869</xmin>
> 
>             <ymin>78401.536498</ymin>
> 
>             <xmax>408875.829430</xmax>
> 
>             <ymax>92579.221325</ymax>
> 
>         </extent>
> 
>         <projections>0</projections>
> 
>         <destinationsrs>
> 
>             <spatialrefsys>
> 
>                 <proj4>+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717
> +x_0=400000 +y_0=-100000 +ellps=airy
> +towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 +units=m
> +no_defs</proj4>
> 
>                 <srsid>2437</srsid>
> 
>                 <srid>27700</srid>
> 
>                 <authid>EPSG:27700</authid>
> 
>                 <description>OSGB 1936 / British National
> Grid</description>
> 
>                 <projectionacronym>tmerc</projectionacronym>
> 
>                 <ellipsoidacronym>airy</ellipsoidacronym>
> 
>                 <geographicflag>false</geographicflag>
> 
>             </spatialrefsys>
> 
>         </destinationsrs>
> 
>     </mapcanvas>
> 
>  
> 
> Old project:
> 
>  
> 
> <mapcanvas>
> 
>         <units>meters</units>
> 
>         <extent>
> 
>             <xmin>400790.090563</xmin>
> 
>             <ymin>86512.592259</ymin>
> 
>             <xmax>401731.465923</xmax>
> 
>             <ymax>87217.568425</ymax>
> 
>         </extent>
> 
>         <projections>0</projections>
> 
>         <destinationsrs>
> 
>             <spatialrefsys>
> 
>                 <proj4>+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717
> +x_0=400000 +y_0=-100000 +ellps=airy
> +towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 +units=m
> +no_defs</proj4>
> 
>                 <srsid>2437</srsid>
> 
>                 <srid>27700</srid>
> 
>                 <authid>EPSG:27700</authid>
> 
>                 <description>OSGB 1936 / British National
> Grid</description>
> 
>                 <projectionacronym>tmerc</projectionacronym>
> 
>                 <ellipsoidacronym>airy</ellipsoidacronym>
> 
>                 <geographicflag>false</geographicflag>
> 
>             </spatialrefsys>
> 
>         </destinationsrs>
> 
>     </mapcanvas>
> 
>  
> 
>  
> 
>  
> 
> 
> James Stott BSc (Hons) MSc | Senior Professional
> Nicholas Pearson Associates | 30 Brock Street | Bath | BA1 2LN
> T: 01225 445548 | M: -
> www.npaconsult.co.uk 
> 
> 
> 
> From: qgis-user-bounces at lists.osgeo.org
> [mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of James Stott
> Sent: 01 November 2011 09:15
> To: qgis-user at lists.osgeo.org
> Subject: [Qgis-user] Scale seems strange in
> 
> 
>  
> 
> Hi all,
> 
>  
> 
> I am having problems with scales on v1.8 (7297b23) from OSGeo4W.
> 
>  
> 
> If I open an existing project everything is fine.
> 
>  
> 
> If I open data in a fresh QGIS session it is reporting strange scales.
> It doesn’t matter what source the data is. For example, I open a
> dataset and it reports 1:784735546. It seems to report correct
> distances. If I pan the scale changes.
> 
>  
> 
> I am using EPSG 27700 (British National Grid). 
> 
>  
> 
> Does anyone have any idea what can be causing this?
> 
>  
> 
> James
> 
> James Stott BSc (Hons) MSc | Senior Professional
> Nicholas Pearson Associates | 30 Brock Street | Bath | BA1 2LN
> T: 01225 445548 | M: -
> www.npaconsult.co.uk 
> 
> Nicholas Pearson Associates, LogoNicholas Pearson Associates, Latest
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> 
> 
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