Re: [jts-dev] snap tolerance on geometry collections

[Martin Davis <mtnclimb@xxxxxxxxx>]

This fix makes sense to me.  

However, as noted on the PR, as of JTS 1.18 the old overlay code (which uses GeometrySnapper) has been superseded by the OverlayNG implementation.  It would be worth trying the geometry failure cases against that code.

Is it possible for you to post some or all of the overlay failure cases you've encountered?

On Sun, Mar 7, 2021 at 7:21 PM Glenn Walbran <glennw@xxxxxxxxxxxxxxx> wrote:

Hi JTS Devs

I've had a few cases of TopologyExceptions when doing a difference on two geometries that were both multipolygons. These geometries both had large envelopes but were made up of much smaller polygons.

After a bit of investigation I worked out that the tolerance being applied in the snapping was much larger than is was when doing a difference on the individual parts.

So I've submitted pull request https://github.com/locationtech/jts/pull/699/ to amend the tolerance calculation to look into the individual parts of the geometry collections.

Let me know your thoughts on that.

Regards

Glenn

--
Glenn Walbran
Software Developer

Catalyst IT - Expert Open Source Solutions
DDI: +64 4 803 2343 | Mob: +64 21 211 1301 | Tel: +64 4 499 2267 | www.catalyst.net.nz



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