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List:       postgis-users
Subject:    Re: [postgis-users] reverseWindingOrder and isClockwise in PostGIS
From:       Paul Ramsey <pramsey () cleverelephant ! ca>
Date:       2009-09-30 18:32:33
Message-ID: 30fe546d0909301132k6447b2c3uc840c6f1f30796ad () mail ! gmail ! com
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Then use ForceRHR to get the rings clockwise followed by Reverse to
get the order you want (counter clockwise).

P

On Wed, Sep 30, 2009 at 11:09 AM, Peter Freimuth <pfreimuth@arcor.de> wrote:
> Picavet Vincent schrieb:
> > Hello,
> > 
> > 
> > > today i am searching for a postgis based solution which gives
> > > me an answer on the question
> > > 
> > > isClockwise(POLYGON)
> > > 
> > > and if this is true
> > > 
> > > reverseWindingOrder(POLYGON)
> > > 
> > > 
> > 
> > PostGIS provides the following function :
> > 
> > ST_ForceRHR(geometry)
> > Force polygons of the collection to obey Right-Hand-Rule.
> > 
> > Does that suit your needs or you really want to test if your polygon is
> > clockwise ?
> > 
> > Regards,
> > Vincent
> > _______________________________________________
> > postgis-users mailing list
> > postgis-users@postgis.refractions.net
> > http://postgis.refractions.net/mailman/listinfo/postgis-users
> > 
> > 
> Hi Vincent,
> thanks for the quick and good response. Yes, i would like to check if
> the vertices of a polygon without inner rings are in a
> clockwise/counterclockwise order so that i can use |ST_Reverse to change
> this.
> At the end i want to dump the coordinates of a polygon in
> counterclockwise order using something like the dump_points function as
> described here
> http://www.spatialdbadvisor.com/postgis_tips_tricks/109/implementing-oracles-getvertices-function-in-postgis-st_dumppoints/
>                 
> !
> Kind regards,
> Peter
> 
> > 
> _______________________________________________
> postgis-users mailing list
> postgis-users@postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 
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