That polygon contains two edges that cross, which is invalid under any
setting.
The setSelfTouchingRingFormingHoleValid parameter only allows situations
where a ring self *touches*, not crosses, AND only for the situation where
the self-touch forms a hole - NOT where it splits the polygon into two
separate areas.
So these are valid with the setSelfTouchingRingFormingHoleValid flag set:
Shell self-touches and isolates a hole:
POLYGON ((100 400, 300 400, 300 300, 150 350, 150 250, 300 300, 300 200,
100 200, 100 400))
Hole self touches to form two separate hole areas:
POLYGON ((100 400, 300 400, 300 200, 100 200, 100 400), (150 350, 250 350,
200 300, 250 250, 150 250, 200 300, 150 350))
and this is not:
Bow-tie - shell split into two areas by a self-touch
POLYGON ((100 400, 300 400, 200 300, 300 200, 100 200, 200 300, 100 400))
On Thu, Jan 14, 2016 at 4:00 PM, John Cartwright - NOAA Federal <
[email protected]> wrote:
> Hello All,
>
> I'm confused about the isValidOp.setSelfTouchingRingFormingHoleValid(true)
> method. Given a bow-tie polygon like the one below, I would have expected
> setting the above option to cause the polygon to report as valid but it
> doesn't.
>
>
> Can someone please clarify for me?
>
> Thanks!
>
> --john
>
> //
> //JTS version 1.14.0 with Groovy 2.4.5.
> //
> wkt = '''POLYGON((1 1, 2 1, 1 2, 2 2, 1 1))'''
> def geom = wktReader.read(wkt)
>
> def validOp = new IsValidOp(geom)
> validOp.setSelfTouchingRingFormingHoleValid(true)
>
> //fails
> assert geom.valid
>
>
>
>
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