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Difference and SymmetricDifference

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Difference and SymmetricDifference

Anke Trittenbach
Hello all together,

i have two questions about the intersections of Primitives of the ISO-Specification 19107.

Initial Situation:
A Point lies on the Interior of a Curve.

1. Curve.difference(Point):

In JTS the result is the whole curve.

But what is the correct ISO-result?? Is it the whole curve too? I think the result is a MultiCurve. The Curve will be splitted at the place of the Point and so the result are two curves in a MultiCurve. The two Curves have one equal boundarypoint where the Point was. But the curve is splitted because Primitives do not contain their boundary.

2. Curve.symmetricDifference(Point)

In JTS the result is the whole curve too.

But I have the same question like before. What is the correctISO-result??


Thank you for your help!!!

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Re: Difference and SymmetricDifference

Martin Davis
Hmm...  Your proposal is a good alternative to the semantics currently
in JTS.

Is there any specification which actually deals with this low-level kind
of issue?

Alternatively, is there a strong use case for this behaviour?

Anke Trittenbach wrote:

> Hello all together,
>
> i have two questions about the intersections of Primitives of the ISO-Specification 19107.
>
> Initial Situation:
> A Point lies on the Interior of a Curve.
>
> 1. Curve.difference(Point):
>
> In JTS the result is the whole curve.
>
> But what is the correct ISO-result?? Is it the whole curve too? I think the result is a MultiCurve. The Curve will be splitted at the place of the Point and so the result are two curves in a MultiCurve. The two Curves have one equal boundarypoint where the Point was. But the curve is splitted because Primitives do not contain their boundary.
>
> 2. Curve.symmetricDifference(Point)
>
> In JTS the result is the whole curve too.
>
> But I have the same question like before. What is the correctISO-result??
>
>
> Thank you for your help!!!
>
>  

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Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022

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