[QGIS-trac] Re: [Quantum GIS] #1373: Derived area values from identify tool differ from calculated PostGIS area

[Quantum GIS]

#1373: Derived area values from identify tool differ from calculated PostGIS area
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        Reporter:  hdus                              |         Owner:  nobody       
            Type:  bug                               |        Status:  new          
        Priority:  major: does not work as expected  |     Milestone:  Version 1.0.0
       Component:  Vectors                           |       Version:  HEAD         
      Resolution:                                    |      Keywords:               
Platform_version:                                    |      Platform:  RedHat       
        Must_fix:  Yes                               |   Status_info:  0            
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Comment (by smizuno):

 Replying to [ticket:1373 hdus]:
 > When I identify a polygon with the identify tool, the derived area
 differs from the calculated area with postgis area(the_geom) function. The
 difference is small but existing:
 >
 > QGIS: 15.516 km2
 >
 > PostGIS: 15.525 km2
 >
 If you are using On-the-fly transformation, the difference is because QGIS
 uses calculation on an ellipsoid rather than plane calculations as PostGIS
 uses for area().

 Without OTF, QGIS uses plane calculations also, but there may still be a
 very small difference.

 This is essentially the same problem as I put in #1219.

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/1373#comment:2>
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