Re: [Jts-topo-suite-user] Polygon union

Michaël Michaud Sun, 17 Nov 2013 17:55:11 -0800

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.

Michaël

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.
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Re: [Jts-topo-suite-user] Polygon union

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