[Qgis-user] Scale seems strange in

Wed Nov 2 03:43:15 PDT 2011

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>

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 <http://www.npaconsult.co.uk/>  

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James Stott BSc (Hons) MSc | Senior Professional
Nicholas Pearson Associates | 30 Brock Street | Bath | BA1 2LN
T: 01225 445548 | M: -
http://www.npaconsult.co.uk/ 

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