[postgis-users] reverseWindingOrder and isClockwise in PostGIS

[Peter Freimuth]

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
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>
>   
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

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