[QGIS-Developer] QGIS gives different area calculation result compared to PROJ

[Denis Rykov]

Thanks for your prompt and detailed reply!

On Fri, Feb 19, 2021 at 5:32 PM Andrea Giudiceandrea <andreaerdna at libero.it>
wrote:

> dr wrote
> > So I would say it seems like an error in the area calculation algorithm
> in
> > QGIS.
>
> Hi,
> there is no unique way to calculate the geodesic area.
>
> For example, PROJ use a C implementation of the GeographicLib algorithm,
> while QGIS uses the same algorithm used by GRASS, SpatiaLite 5 uses RTTOPO
> library and PostGIS uses GeographicLib.
>
> See this recent threed
>
> http://osgeo-org.1560.x6.nabble.com/Confusion-with-ellipsoidal-method-of-area-td5454013.html
> on the same topic.
> There are two feature requests for QGIS and GRASS:
> https://github.com/qgis/QGIS/issues/40888
> https://github.com/OSGeo/grass/issues/1235
> and a Pull Request in GRASS https://github.com/OSGeo/grass/pull/1283.
>
> So it look like there is the possibility that GRASS will switch to use the
> same C implementation of the GeographicLib algorithm used by PROJ.
>
> Regards.
>
> Andrea
>
>
>
> --
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