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

[Helmut Kudrnovsky]

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|
> 
> 
> 
> -----
> best regards
> Helmut
> --
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forwarding from the GRASS GIS dev ML:
[https://lists.osgeo.org/pipermail/grass-dev/2018-October/090080.html]

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On Tue, Sep 25, 2018 at 7:38 PM Helmut Kudrnovsky wrote:
>
> fyi see
>
https://lists.osgeo.org/pipermail/qgis-developer/2018-September/054644.html
>
> with GRASS mentioned
> ------------------
> Kristian Evers:
>
> Right, here are the calculated areas as returned by a number of different
> GIS applications and the planimeter app of GeographicLib for reference:
>
> 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

adding to the confusion:

I used the geographiclib API as included in PROJ 5.2.0 following the
example for geod_polygonarea() in geodesic.h and get
geographiclib: 14,737.935 km^2
quite different from
Planimeter: 14,722.522 km^2

GRASS native gives 14,718.097679
as also reported by Helmut and Stefan

Markus M
------------------------------------------



-----
best regards
Helmut
--
Sent from: http://osgeo-org.1560.x6.nabble.com/QGIS-Developer-f4099106.html