Hi, To complete Nicolas answer, you should check what are the measurements options set in Project --> Project Properties --> General tab. See also http://docs.qgis.org/2.14/en/docs/user_manual/introduction/general_tools.html#measuring
2016-10-12 14:07 GMT+02:00 Nicolas Cadieux <[email protected]>: > 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] <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5290417&i=0>> 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 [hidden email] > <http:///user/SendEmail.jtp?type=node&node=5290417&i=1> > To unsubscribe from Quantum GIS - User, click here. > NAML > <http://osgeo-org.1560.x6.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > > > ------------------------------ > View this message in context: Re: inconsistenty when calculating area > depending on file type or projection? > <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 > <http://osgeo-org.1560.x6.nabble.com/Quantum-GIS-User-f4125267.html> at > Nabble.com. > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: http://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user >
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