Re: [Jts-topo-suite-user] JTS Overlay operation

[Michaël M. <mic...@fr...>]

Hi,
> if you spot any other documentation or FAQ issues I'm happy to hear 
> about them!
As you invite me...

UnaryUnionOp javadoc explains that unioning an empty list
will return a POINT EMPTY and after, that return value will be a
empty GEOMETRYCOLLECTION :
http://tsusiatsoftware.net/jts/javadoc/

Indeed, if no GeometryFactory is provided, union returns null,
else if it returns an empty GEOMETRYCOLLECTION
It makes sense but would need to be clearly  documented,
especially for the null return case which may cause troubles.

Regards,

Michaël


>
> On Tue, Dec 18, 2012 at 12:54 PM, Michaël Michaud 
> <mic...@fr... <mailto:mic...@fr...>> wrote:
>
>     Hi,
>>     Ah, ok, that sounds like the classic "polygonal coverage overlay"
>>     problem.  The current JTS approach for this problem is here:
>>
>>     http://tsusiatsoftware.net/jts/jts-faq/jts-faq.html#E3
>     Oh, yes.
>     I've followed this approach a couple of times (in OpenJUMP noder
>     and in
>     OpenJUMP PlanarGraph plugin I think),
>     I found that determining the parentage is more difficult than it seems
>     because noding slightly change geometries and because I was
>     relying on
>     Interior Point for the PIP test and at that time, InteriorPoint
>     could be on a
>     polygon boundary (don't remember if it is fixed).
>
>     By the way, I'll read the FAQ before my next question ;-)
>
>
>
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