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Extract area overlap of two polygon boundaries


buckrogers
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Hello,

I have two polygon datasets: folios and townlands(see image below). For the most part, the folios(grey outline) are nested neatly within the townlands dataset(red outline) so the outer folio boundaries are shared with the townlands’ boundaries. I would like to extract the areas where these two datasets’ polygon boundaries cross...i.e. where they are not nested neatly. Most of these will be slivers.  SpatialRelator(and Tester) helps to extract the offending folios using the Spatial Predicates Test: "Requestor OGC-Overlaps Supplier" however the output is the entire folio polygons(not overlapping area) as SpatialRelator does not edit the input dataset. I am unsure as to what to do next, I would like to automate this process in FME Server if possible so having one workflow would be useful.

 

Best answer by liamfez

It sounds like the Clipper may be the transformer you are looking for. With the Townlands as the Clipper and the Folios as the Clippee, any Folio which crosses a Townlands’ boundary would be split. If the Folios have an attribute for what Townland they belong to, you can then use the Group By function and the section of the Folio which is outside of its Townland would be sent to the Outside port.

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2 replies

liamfez
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  • Best Answer
  • March 15, 2024

It sounds like the Clipper may be the transformer you are looking for. With the Townlands as the Clipper and the Folios as the Clippee, any Folio which crosses a Townlands’ boundary would be split. If the Folios have an attribute for what Townland they belong to, you can then use the Group By function and the section of the Folio which is outside of its Townland would be sent to the Outside port.


buckrogers
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  • March 18, 2024

@liamfez Thank you – yes, this is exactly the process that I am looking for. 


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