Question

PointOnArea overlayer creating duplicate points on output

  • 15 April 2016
  • 4 replies
  • 9 views
H

I have about 60000 points and 25000 polygons going into a pointonareaoverlayer. The overlayer works fine and the points are picking up the attributes from the polygons.

But, duplicates of the points are being created in the output. 3 or 4 duplicates are created for each point with the exact same attribute data - so I'm getting over 200000 points on output. I know I can use duplicate remover to get rid of them, but these duplicates shouldn't be created in the first place.

Any ideas on why this would be happening and how to fix it?

4 replies

takashi
Rank
Userlevel 2
Badge +17

Hi @hear_it_here, sounds strange. Is the number of points (200000) counted at the output port of the PointOnAreaOverlayer? Or is it counted after processing by some other transformers?

H

Hi @hear_it_here, sounds strange. Is the number of points (200000) counted at the output port of the PointOnAreaOverlayer? Or is it counted after processing by some other transformers?

These duplicates are coming right out of the point output port.

roland.martin
Badge +7

Just as an experiment, try running the points through a Deaggregator before the PointOnAreaOverlayer. It sounds as though you might have aggregate points ("multipoints" in Esri language) in your dataset at the same geographical location - I think aggregate features are automatically deaggregated by the Overlayer transformers in case some parts of the feature overlay and others don't.

If this is the problem, you can fix it by putting a Counter before the Point input to generate a unique ID, and then adding an Aggregator after the PointOnAreaOverlayer using the unique ID as the Group By. Or, since you're getting duplicate locations, a Matcher might be more useful here.

fmelizard
Rank
Userlevel 4
Badge +13

Just as an experiment, try running the points through a Deaggregator before the PointOnAreaOverlayer. It sounds as though you might have aggregate points ("multipoints" in Esri language) in your dataset at the same geographical location - I think aggregate features are automatically deaggregated by the Overlayer transformers in case some parts of the feature overlay and others don't.

If this is the problem, you can fix it by putting a Counter before the Point input to generate a unique ID, and then adding an Aggregator after the PointOnAreaOverlayer using the unique ID as the Group By. Or, since you're getting duplicate locations, a Matcher might be more useful here.

I agree, most likely suspect is that there were aggregate points going in. They do get deaggregated. If not, please be in touch with support@safe.com

See an example of this in:

testmultipointinoverlay.fmw (run with full inspection to see the results)

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