[postgis-users] Polygon problem in Lon/Lat SRID 4326

Carlos Ferrão cferrao at gmail.com
Thu May 18 11:47:14 PDT 2006

Hello all,
I am using a Geometry data type to store Polygons in Lon/Lat
coordinates with the SRID 4326.
I created the database, ran the lwpostgis.sql and spatial_ref_sys.sql.
I added the geometry column with SELECT

For most of my polygons everything seems ok. However, the polygons
which have one of its points in the other side of the time limit are
considered invalid (isValid='f') and the polygon is stored as if my
world is flat and not a sphere (doesn't connect the 180 to the -180

For instance, defining POLYGON((177.87 72.75,-179.15 72.4,174.19
66.05,173.92 65.7,171.66 65.98,171.91 66.33,177.87 72.75)) returns a
polygon whose vertices cross the whole world as the second longitude
is a negative value. As you can see, the polygon points are defined in
a clockwise order.

What is the correct way to define a polygon in this case? Do I have to
translate my coordinates somehow?

Thanks in advance,
Carlos Ferrao

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