[postgis-users] Is there a standard direction for polylines?
graham.rick at gmail.com
Wed Mar 11 09:44:24 PDT 2009
On Wed, Mar 11, 2009 at 12:26 PM, Paul Ramsey <pramsey at opengeo.org> wrote:
> 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.
Thanks Paul, I did find that. Since there is no standard direction
for simple polygons, I can use clockwise, secure in the knowledge that
I'm not going against the grain.
> 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?
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>> postgis-users at postgis.refractions.net
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