[geotk] Circle Polygon

Martin Desruisseaux martin.desruisseaux at geomatys.fr
Wed Sep 16 04:24:25 EDT 2009

theuns a écrit :
> I displayed a world shapefile using the EPSG:3395 projection.
> and draw 4 circles with radius 50km.
> This is the places(more or less) where i draw them , and i measured the
> diameter across the with and height, of the circle.
> 1. Equator , width +-100km , height +- 100km 
> 2. Cape Town (SA) , width +-82km , height +- 82km
> 3. Southern Tip of South America , width +-57km , height +- 57km
> 4. Northern Part Greenland , width +-14km , height +- 14km
> So the circle's diameter does take off further away from the equator,
> and like Adrian said, it should be egg shaped (eclipses), but the circle
> stay round?	

This is true that if the Data CRS is Mercator and the renderer Objective CRS is 
Geographic (or the converse; Geographic Data CRS and projected Objective CRS), I 
would expect egg shaped ellipses. If both the Data CRS and Objective CRS are the 
same projection, then the shape would stay as in the data but I would not expect 
a change of circle size neither...

In order to figure out what is happening, I would need to know the rendering 
chain: data CRS, objective CRS and which API is used for rendering the circles...


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