[postgis-users] different results for area with different programms

[Sandro Santilli]

On Thu, Feb 23, 2012 at 07:13:12AM -0800, Martin Davis wrote:
> I wonder about the PostGIS value, too. JTS gives 9.336164500133789.

Martin, JTS area calculator changed too recently
(the shoelace formula). Could that explain ?

BTW, here's what I get with PostGIS 2.0.0alpha7SVN:
 9.33616450013379

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> On 2/23/2012 6:58 AM, Astrid Emde wrote:
> >Hello,
> >
> >I calculate the area of polygons and get different results with diffrent
> >programms.
> >
> >Here is an example polygon:
> >
> >Select st_area(geometryfromtext(
> >'POLYGON ((
> >   2569220.83 5630370.607,
> >   2569215.357 5630374.968,
> >   2569216.017 5630375.795,
> >   2569216.19 5630376.01,
> >   2569221.663 5630371.649,
> >   2569220.83 5630370.607
> >))',31466) );
> >
> >These are the results that I get:
> >* PostGIS: 9.337890625 (with "POSTGIS="1.5.1" GEOS="3.2.0-CAPI-1.6.0")
> >
> >* AutoCAD Map 2012: 9.3362
> >* Kanal++ [1]: 9.3361645
> >
> >PostGIS gives back a slightly bigger area than the other programms. Do you
> >
> >know why and who is right?
> >
> >Best regards
> >
> >Astrid
> >
> >[1]
> >http://tandler.com/communal_gis/watermanagment/wastewater/sewer-gis-kanalplusplus.htm
> >
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