Re: [jts-dev] Struggling with polygon topology again. Overlapping inner

[Phil Scadden <p.scadden@xxxxxxxxxx>]

>1. For polygons which have "loops" in their shell, buffer(0) may FAIL because it keeps only one of the loops (and may choose the smaller one).

>2. For polygons with rings that touch but do not cross, buffer(0) should produce VALID output

That is excellent information. What about the more common case of internal rings that overlap?

>>I see the getArea works on invalid polygons so I have put in a filter to which compares areas before and after buffer(0). If "significantly" different, then revert to difference method.

>That's a reasonable approach.

I now have a log from a run, where I did this. The filter fired quite a few times so I am looking forward analyzing what worked and what didnt. (When it failed, it fell back on difference method). The final output is looking good however, and the input was truly awful for complexity.

--
Phil Scadden, Senior Scientist GNS Science Ltd 764 Cumberland St, Private Bag 1930, Dunedin, New Zealand Ph +64 3 4799663, fax +64 3 477 5232

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