[postgis-users] problem with polygons spanning across 180E

Paul Ramsey pramsey at opengeo.org
Sun Mar 15 18:18:09 PDT 2009

None of the systems mentioned understand geographic coordinates as
having a "wrap point" at 180. They are treated as planar, naturally
your polygons connect across the central meridian instead of the

The only "solution" is to force your data to respect the dateline by
cutting it in half at 180/-180


On Sun, Mar 15, 2009 at 3:03 PM, sige <sigenz at yahoo.co.nz> wrote:
> Hi
> I have a problem with polygons spanning across the meridian (180E degrees),
> for example: 45 176,  46 178, 46 -178, 45 -179, 44 179, 45 176 in a circle.
> I inserted those records into PostGIS using WKT and the GeomFromText
> function well. However the polygons dont show up correctly on either UDig or
> OpenLayers: they are cut into two parts at 180E and connected from back to
> back with long horizontal lines. I an not sure if this is a problem with the
> data in PostGIS or the SW for displaying the data.
> Any body has come across this problem and any ideas?
> Thanks
> Sige
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