[Qgis-user] Scale seems strange in
James Stott
James.Stott at npaconsult.co.uk
Fri Nov 4 02:15:43 PDT 2011
Thanks for the response and your explanation. It helped to cement what I
already thought.
My point is I think something has gone strange with EPSG 27700 in QGIS
at the moment. It works fine on 1.7.1 and not on the OSGeo4W 1.8.0-120.
It never used to set the units to degrees - it should be metres.
I think that QGIS is getting the default units wrong for 27700. The
coordinate system definition states that the units should be m.
I am also reporting this behaviour on my windows computer at home
(completely separate to the computers we have the issue on at work) and
a computer using Ubuntu 11.10. And on a windows machine on (1.8.0-78) it
works fine.
I have also noticed a change in the behaviour of Save As... When
exporting to MapInfo MIF. Previously QGIS was getting the export wrong
and using BNG with WGS84, now it is exporting it to BNG with OSGB36
(which is correct).
From: kidsmake6until2019 at gmail.com [mailto:kidsmake6until2019 at gmail.com]
On Behalf Of Brad Nesom
Sent: 02 November 2011 19:49
To: James Stott
Cc: Saber Razmjooei; qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] Scale seems strange in
so did you understand why?
lat lon is not an equidistant coordinate system. It is an angular
measure. The graticules merge closer togehter the further north they go.
When you overlay data projected to ll onto a flat surface the lengths
east west at the top are shorter than the lengths east west at the
bottom.
that is what is changing the scale because without zooming the scale of
the objects would change by panning the map north and south.
Nothng about the scale is changing except the distance measured across.
No coordinate values.
HTH
On Wed, Nov 2, 2011 at 10:12 AM, James Stott
<James.Stott at npaconsult.co.uk> wrote:
If I use the arrow keys to pan north and south the scale changes. If I
use them to pan left and right it doesn't change.
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/>
From: kidsmake6until2019 at gmail.com [mailto:kidsmake6until2019 at gmail.com]
On Behalf Of Brad Nesom
Sent: 02 November 2011 15:00
To: James Stott
Cc: Saber Razmjooei; qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] Scale seems strange in
I am thinking rather than that it is just the fact that when you use
degrees, moving in the map would give you a different scale.
Because every time you move north or south you have changed the length
of the x distance.
If you pan left and right (very carefully) do you see the scale not
change?
On Wed, Nov 2, 2011 at 9:02 AM, James Stott
<James.Stott at npaconsult.co.uk> wrote:
Could this just be a windows thing then? I tried an older version of
qgis-dev (1.8.0-78) on a different windows machine in the office and
there are no problems. Metres should be the default setting for 27700
shouldn't it not degrees?
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/
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/
-----Original Message-----
From: Saber Razmjooei [mailto:razmjooeis at faunalia.co.uk]
Sent: 02 November 2011 10:48
To: James Stott
Cc: qgis-user at lists.osgeo.org
Subject: RE: [Qgis-user] Scale seems strange in
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-projection
s-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 <http://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 <http://www.npaconsult.co.uk/>
>
> Nicholas Pearson Associates, LogoNicholas Pearson Associates, Latest
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