Thanks Micheal, good point. Yes, i use JTS Conformal Delaunay Triangulation
with edge enforcement with a small tolerance (0.001). As you mentioned, it
introduces steinar paoints that are not in the polygons. If i stick with
Conformal Delaunay Triangulation, any solution to overcome
this? Otherwise, i can use your Polygon triangulation to triangulate space
between the two polygons. I think again it might introduce the same
problem, when deriving the space by subtracting the union of polygons from
the ConvexHull!!!. Any idea is appreciated.
Brian.
On Mon, Nov 18, 2013 at 1:54 AM, <
[email protected]> wrote:
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> 1. Re: Polygon union (Brian Sanjeewa Rupasinghe)
> 2. Re: Polygon union (Micha?l Michaud)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Sun, 17 Nov 2013 10:24:50 +0000
> From: Brian Sanjeewa Rupasinghe <[email protected]>
> Subject: Re: [Jts-topo-suite-user] Polygon union
> To: [email protected]
> Message-ID:
> <CAEMA-4h+_w7o0=
> [email protected]>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi, Micheal
>
> Thanks for the reply. My use case is to add triangles between a pair of
> polygons to get the amalgam. My polygons are in PostGIS
> and what i do is, i get the union of polygon pair with a query in PostGIS
> and output is converted into JTS and triangulated.
> Then i find the triangles between them and add all of them with the union
> pair. So the final result should be a polygon which does
> not happen always. Where should i exactly apply geometry precision
> reduction. Is it only to the union geometry from PostGIS or
> do i need to apply it to output triangles as well?
>
> Brian.
>
>
> On Sat, Nov 16, 2013 at 6:43 PM, Brian Sanjeewa Rupasinghe <
> [email protected]> wrote:
>
> > Hi,
> >
> > I need to union adjoining polygons together. I use UnionWithUnionOp()
> > method in JTS 1.13.
> > However, sometimes, even if i reduce the geometry precision, it does not
> > end up with a unique polygon resulting a multi-polygon. In such instances
> > which method is the best to
> > avoid creating multi-polygon? I used buffer(0), but it did not work. What
> > about adding a small +- buffer?
> >
> > Brian.
> >
> -------------- next part --------------
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> ------------------------------
>
> Message: 2
> Date: Sun, 17 Nov 2013 12:26:57 +0100
> From: Micha?l Michaud <[email protected]>
> Subject: Re: [Jts-topo-suite-user] Polygon union
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi,
>
> Do you use a constrained triangulation or not ?
> How do you find triangles between your polygons ?
> Possible problems I can see are :
>
> Triangulation without constraint : some triangles may be
> partly on your polygon (green) and partly in the gap (blue)
>
>
> Triangulation with constraint : triangles "seem" to fill the gap,
> but some vertices are not part of the original polygons. Depending on
> how you find the triangles lying in the gap, you may miss some.
>
>
> Micha?l
> > Hi, Micheal
> >
> > Thanks for the reply. My use case is to add triangles between a pair
> > of polygons to get the amalgam. My polygons are in PostGIS
> > and what i do is, i get the union of polygon pair with a query in
> > PostGIS and output is converted into JTS and triangulated.
> > Then i find the triangles between them and add all of them with the
> > union pair. So the final result should be a polygon which does
> > not happen always. Where should i exactly apply geometry precision
> > reduction. Is it only to the union geometry from PostGIS or
> > do i need to apply it to output triangles as well?
> >
> > Brian.
> >
> >
> > On Sat, Nov 16, 2013 at 6:43 PM, Brian Sanjeewa Rupasinghe
> > <[email protected] <mailto:[email protected]>> wrote:
> >
> > Hi,
> >
> > I need to union adjoining polygons together. I
> > use UnionWithUnionOp() method in JTS 1.13.
> > However, sometimes, even if i reduce the geometry precision, it
> > does not end up with a unique polygon resulting a multi-polygon.
> > In such instances which method is the best to
> > avoid creating multi-polygon? I used buffer(0), but it did not
> > work. What about adding a small +- buffer?
> >
> > Brian.
> >
> >
> >
> >
> >
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