[Qgis-developer] Derived Area is calculated wrong

[Radim Blazek]

Are there islands in the polygon? Can you check is island
presence could cause the error?

Radim

On 8/8/06, Maciej Sieczka <tutey at o2.pl> wrote:
> Hi,
>
> (I'm reposting this, as my first attempt was filtered out by anti-spam
> and on the second attempt, forwarded by Tim, nobody replied.)
>
> This is a serious issue. Is it a bug or user/setup problem?
>
> There is a vector polygon Grass layer. It's area is, according to
> 'v.to.db option=area units=k', 32281.680484. Also d.what.vect reports
> "area size: 32281680484.380993". These seem correct, as after
> rasterising it in Grass at 10m resolution the raster non-null area
> (r.stats -a) is very close: 32281681800.000000.
>
> However, querying the same vector exported to shapefile (v.out.ogr
> type=area) in QGIS 0.8 (current SVN) returns '(Derived) Area 32303.759
> km2'. It's 22 km2 more!
>
> Querying the polygon Grass vector itself in QGIS returns the same wrong
> derived area too.
>
> The more complicated shape, the bigger the difference.
>
> Could somemebody investigate? The shapefile is attached.
>
> Maciek
>
>
>
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