Hi,
> I am comparing two datasets of polygons using ChangeDetector, matching
> on Geometry only (2D). The problem is that in some cases, there is
> negligible change in the polygons. And these negligible changes resuls
> in records being added to the "Added" and "Deleted" outputs.
>
> I would like for those changes in polygon area which I consider
> negligible (say under 1 square foot) to be either disregarded or
> categorized separately so that my sets of "Added" and "Deleted" are
> smaller and more manageable.
>
> Anyone know of a way to achieve this?
Well... negligible change is still change :) The trouble with automatic
vs human processing on this is that it's very hard to give the automatic
way the same 'fuzzy logic' as a human operator would apply.
There's several things you can try:
1:
- OGCGeometryExtractor on the new features to save the new geometry
- AnchoredSnapper with a certain tolerance to snap new back to old
- ChangeDetector
- OGCGeometryReplacer to bring back the new geometry
2:
- Calculate area for old and new
- Matcher (assuming there is some unique id)
- ExpressionEvaluator and Tester to calculate and test for the
difference in area
The area-calculation route is a bit risky, you can have a wildly
different polygon, but still have exactly the same amount of sq. feet.
Hope this helps.
--
Hans van der Maarel
Red Geographics
Zevenbergsepoort 44b www.redgeographics.com
4791 AE Klundert [EMAIL PROTECTED]
The Netherlands phone: +31-168-401035
For insights into what's up at Safe Software and what's on the development
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Safe Software has also made slides available that outline enhancements planned
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of the FME Worldwide Users Conference. To view these slides, visit
www.safe.com/2006uc.
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