[geotk] Circle Polygon

theuns theunsheydenrych at gmail.com
Tue Sep 15 03:55:07 EDT 2009

HI Martin
I am trying to create a circle polygon, by using the JTS geometry
point.buffer(int) method.
The code i use, to achieve this is as follows.

Geometry buffer = point_geom.buffer(2000) ;

I suspected the circular buffer  to be 2000m radius , since a am using
EPSG:3395 , the Mercator projection, but the circle is 1800m in

I collaborated with Johann, and he suggested that i must try to create a
circle closer to the equator, and see what the result there is , and yes
the results is better, the circle do have a radius of 2000m.

So the more south or north i create the circle it will render less than
the input radius.
I have a suspicion that if i work the values for the circle out manually
i will end up with the same result, because of the renderer using the
same CRS to render. 

1.What exactly is the cause of this?
2.Is there a way to get the circle rendered correctly?
3.Is there maybe a error value to be added to the radius, the more you
move away from the equator?

Thank you in advance

Theuns Heydenrych

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