[postgis-users] Is there a standard direction for polylines?

Paul Ramsey pramsey at opengeo.org
Wed Mar 11 09:26:09 PDT 2009

There isn't a standard, but you can force your polygons into an
orientation with ST_ForceRHR, which forces a clockwise orientation for
exterior rings and anti-clockwise for interior rings.


On Tue, Mar 10, 2009 at 3:20 PM, Rick <graham.rick at gmail.com> wrote:
> I'm fairly new to this.
> I have a requirement to do calculations on runways in aerodrome maps.
> I orient the runway centerlines west to east so that the low runway
> number is at the start of the line.
> I'm doing a similar, more complex normalization to the runway outline,
> the first vector crosses the start of the centerline.  Whether they
> are clockwise or ccw doesn't matter to me as long as it is always the
> same.  Is there a standard insidedness for polygons which would
> dictate a direction?
> --
> Cheers!
> Rick.
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