[gdal-dev] Polygon winding order in ogrinfo output

[Frank Warmerdam]

Roger André wrote:
> Just a quick question to find out how the clockwise winding order is 
> established in ogrinfo output.  Is this because the original data file 
> being read was created with the polygons in that order, or is it a 
> "feature" of ogr's?

Roger,

OGR uses the simple features geometry model which places no requirements
on the winding direction of polygon rings.  So generally speaking the
winding direction is not defined - often it will be whatever was most
convenient when reading from the source files.

The Shapefile *writer* does have to rewind polygon rings to put them into
the required winding order for shapefiles.

Best regards,
-- 
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