Hello, Thanks for the reply. I don't have SAGA or PostGIS set up at the moment. (have sent Stefan the shapefile off-list).
Moritz - I know that the QGIS value is true. The polygon has been drawn over a feature on a raster image (which I know is correct in its dimensions). Thanks James On 19 May 2017 at 08:36, Moritz Lennert <mlenn...@club.worldonline.be> wrote: > On 18/05/17 18:41, Blumentrath, Stefan wrote: > >> Hi James, >> >> QGIS uses a ellipsoidal area measurement, while GRASS (like most of the >> other GIS) uses a Cartesian measurement (others, please correct me if that >> is not the case in WGS84). >> >> See amongst others: >> https://issues.qgis.org/issues/12057 and >> https://issues.qgis.org/issues/14675 >> >> Would you mind comparing area measurement of a third software (SAGA, >> PostGIS, ...)? >> > > I would suggest making tests with polygons of which you know the area > (e.g. simple squares to begin with) > > Moritz > -- *James Duffy* PhD Researcher Environment and Sustainability Institute Penryn Campus University of Exeter Penryn Cornwall TR10 9FE
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