[QGIS-Developer] [Qgis-user] New Features in Shape Tools 3.2.0

[C Hamilton]

Nyall,

Thanks so much for investigating and fixing this. Also thank you all who
have contributed to this discussion. This was an important bug to find and
fix. I think we will find that the geographiclib calculations are going to
be slightly more accurate coming in at 14.737 km^2, but the GRASS
calculations are quite accurate.

Calvin


On Mon, Oct 1, 2018 at 11:12 PM Nyall Dawson <nyall.dawson at gmail.com> wrote:

> On Mon, 1 Oct 2018 at 23:01, Helmut Kudrnovsky <hellik at web.de> wrote:
> >
> > Helmut Kudrnovsky wrote
> > >>[...]
> > >>Caris LOTS: 14.737 km^2
> > >>ArcMap:     14.727,446 km^2
> > >>MapInfo:    14.727,352 km^2
> > >>GeoMedia:   14.726,443 km^2
> > >>Planimeter: 14.722,522 km^2
> > >>QGIS 3.2:   14.652,181 km^2
> > >>QGIS 2.8:   14.652,181 km^2
> > >>[...]
> > >>My suspicion is that the geodesic algorithm used by QGIS (and
> apparently
> > > GRASS) is to blame here.
> > >
> > > a quick check in GRASS 7.7.svn shows :-)
> > >
> > > |m2|km2|
> > > |14718097678,673|14.718,097679|
>
> Ok, with https://github.com/qgis/QGIS/pull/8090 QGIS now exactly
> matches GRASS' value (14.718 km2).
>
> (For reference -- not a regression, this bug has been around since
> ellipsoidal calculations were introduced to QGIS!)
>
> Nyall
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