[Qgis-user] Field Calculator calculates negative area

[Ziegler Stefan]

Hi 

Perhaps the value is too large for the field definition. Looking at your shapefile the attribute "Areal" can store integer values up to 10 digits. So you have to define an attribute that can store more than 10 digits.

Regards
Stefan 


> -----Ursprüngliche Nachricht-----
> Von: qgis-user-bounces at lists.osgeo.org [mailto:qgis-user-bounces at lists.osgeo.org] Im
> Auftrag von magerlin
> Gesendet: Montag, 25. März 2013 16:08
> An: qgis-user at lists.osgeo.org
> Betreff: [Qgis-user] Field Calculator calculates negative area
> 
> Hi
> 
> I wanted to calculate the areas of some polygons and used the $area in the field
> calculator.
> 
> But one of my (rather complicated) polygons ended up having a negative area.
> 
> As can be seen from the below screen shot the derived area from the identify tool is
> correct (a least it is positive) while the value Areal which I calculated is negative:
> 
> <http://osgeo-org.1560.n6.nabble.com/file/n5042754/Negative_Area.png>
> 
> A peculiar thing is that until I save my shape file the area is correct in the field
> calculator (Area2 is no saved yet):
> 
> <http://osgeo-org.1560.n6.nabble.com/file/n5042754/Negative_Area2.png>
> 
> The shap file can be doanloaded here:  Storzoner.zip <http://osgeo-
> org.1560.n6.nabble.com/file/n5042754/Storzoner.zip>
> 
> Also Version 1.9 calculates a negative value even thoug it firsts show up when I close
> and reopen the attribute table.
> 
> 
> 
> 
> 
> 
> 
> -----
> Regards Morten
> 
> Qgis 1.8.0 Stand alone installer in Win7 64 bit
> --
> View this message in context: http://osgeo-org.1560.n6.nabble.com/Field-Calculator-
> calculates-negative-area-tp5042754.html
> Sent from the Quantum GIS - User mailing list archive at Nabble.com.
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user