[Qgis-user] inconsistenty when calculating area depending on file type or projection?

[Nicolas Cadieux]

Hi,
You may be calculating square degrees and not metres.  It can depend on the crs depending on the tools you are using.
Nicolas

> Le 11 oct. 2016 à 08:54, Martina Schäfer [via OSGeo.org] <ml-node+s1560n5290228h29 at n6.nabble.com> a écrit :
> 
> I experienced some confusion with calculation of area using the field calculator in QGIS version 2.16.3. Since I'm using MapInfo Professional as well, I mainly use tab-files that I can open in both programmes, but occasionally I save as shapefile since this used to be the default in QGIS. 
> 
> When comparing files, I coincidently realized that there was a mismatch in calculated area for the shapefile and the tab-file for exactly the same polygons! I used the field calculator in the attribute table in both cases, but for the shapefile the resulting areas were almost doubled in area compared to the tab-file. Any idea why this is happening? 
> 
> I also realized similar differences when calculating area in a file where projection has been converted from SWEREF99TM (a Swedish national projection) to WGS84. There differences occurred in both the tab and shapefile compared to the area calculated for the same tab-file in MapInfo. Again I find this very confusing! 
> 
> I need to rely on the area-calculations thus I really hope someone here can explain to me what is happening! 
> 
> Thanks in advance, 
> Martina 
> 
> 
> 
> 
> If you reply to this email, your message will be added to the discussion below:
> http://osgeo-org.1560.x6.nabble.com/inconsistenty-when-calculating-area-depending-on-file-type-or-projection-tp5290228.html
> To start a new topic under Quantum GIS - User, email ml-node+s1560n4125267h38 at n6.nabble.com 
> To unsubscribe from Quantum GIS - User, click here.
> NAML




--
View this message in context: http://osgeo-org.1560.x6.nabble.com/inconsistenty-when-calculating-area-depending-on-file-type-or-projection-tp5290228p5290417.html
Sent from the Quantum GIS - User mailing list archive at Nabble.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20161012/e9e1481e/attachment.html>