Question

Why attribute is missing after area on area overlay?

smfks911

Hi altruist,

I am having an issue in after using AreaOnArea overlay operation. I have overlaid two polygon datasets and ideally the output should have attributes from layer when there is _overlap field have 2 and more. This is what happened for other overlay operations. However, in the following cases I do not see the attribute from one of the polygons after the overlay operations:

 

This is the attributes before overlay:

HeritagetableThe overlay operations:

HeritageOverlayAfter the overlay:

HeritageOverlayTableDoes anyone have idea why that may happen?

4 replies

todd_davis
Rank
Userlevel 1
Badge +12

Yes!

 

You are using the AreaonAreaOverlayer Transformer, which is finding overlaps in you cadastre layer as well as against the CLEP boundaries. e.g. to prove, disable the CLEP input and you will still get heaps of overlaps and more features than you input.

 

You should be using a different transformer for that type of operation, one that seperates the inputs into on that is supplying and one that is receiving. But which one, depends on your specific needs. So you could be using Clipper (most obvious choice based on what you are doing so far), SpatialRelator or SpatialFilter.

 

Cheers,

Todd

 

 

smfks911

Yes!

 

You are using the AreaonAreaOverlayer Transformer, which is finding overlaps in you cadastre layer as well as against the CLEP boundaries. e.g. to prove, disable the CLEP input and you will still get heaps of overlaps and more features than you input.

 

You should be using a different transformer for that type of operation, one that seperates the inputs into on that is supplying and one that is receiving. But which one, depends on your specific needs. So you could be using Clipper (most obvious choice based on what you are doing so far), SpatialRelator or SpatialFilter.

 

Cheers,

Todd

 

 

Hi @Todd Davis​ , Thanks. but I used this transformer before to calculate proportion (%) of one layer. This transformer should work same as the intersection does in GIS. So consider like the overlay of this hatched area with a property lot underneath it:

 

HeritageOverlayQGISThen after the area on area overlay in FME, the following part is for where both overlapped:

HeritageOverlayBothMy question is it normal that the overlaid part will miss entire attributes from one of the input layer? I actually want to calculate % of the heritage layer on the property parcel and I followed same procedure for other zoning layer. Not sure why its not happening here. SpatialFilter does select the intersecting Lots but that does not help to calculate %.

M
Badge +2

@smfks911​ It depends on the settings of the AttributeAccumulation parameters whether AreaOnAreaOverlayer will preserve attributes or not. Try the Merge Incoming Attributes option.

dialog

smfks911

@smfks911​ It depends on the settings of the AttributeAccumulation parameters whether AreaOnAreaOverlayer will preserve attributes or not. Try the Merge Incoming Attributes option.

dialog

Thanks so much @Mark Stoakes​. It worked 😊

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