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On Thu, Jun 13, 2013 at 5:14 PM, Norman Langner <
[log in to unmask]> wrote:

I'm curious how geomason handles geographic references. I'm importing a
> shapefile with  polygons in the WGS84 reference system. All the points have
> values like 52.03N 7.63E. When I measure the polygon area with a gis then I
> get different values than using the getArea on the polygons geometry.
> Even when I accept that getArea gives me the area in degrees it isn't the
> same mē after I convert the value.
>
> I found nothing in the api or the other doc sources where this part is
> described.
> Now I'm not sure what to do. Am I making a mistake or do I miss something?
>
>
GeoMASON is not a GIS; its geometric operations are geospatial agnostic in
that it treats geometry as plain geometry.  So, in the case of WGS84 data
that's really on an ellipsoid, you'll get different values from GeoMASON
because the areas it calculates are on the Euclidean plane and not an
ellipsoid.

If it's important for you to have access to the actual area from within
GeoMASON, I suggest calculating the area within a proper GIS application,
adding that as an attribute, and then accessing that attribute from within
the simulation.  An alternative approach is to reproject the data to UTM,
which is in meters and "flattened", and then calculate the area from within
GeoMASON.  However, be aware that projecting warps the underlying data, so
it still won't be 100% accurate.