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

[Astrid Emde]

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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