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

[Carlos Cerdán]

AFAIK, It also is needed to turn off "on the fly SRC transformation" to get
correct area values.... Or QGIS has fixed this point?

If you can't get correct area values, check out about it....


2016-10-12 7:40 GMT-05:00 DelazJ <delazj at gmail.com>:

> 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 <nicolas.cadieux at archeotec.ca>:
>
>> 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
>>
>>
>>
>>
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