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Question

Spatial Relator not relating two touching polygons.

bjudes
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Hi,

I have 399 polygons that I want to dissolve on their nearest neighbour. I'm using the spatial relator to create an id between the polygons to be dissolve and the polygon they will be dissolve on. In the vast majority of instances when I run these polygons through the spatial relator it works. For example if a polygon to be dissolved touches another polygon it will get a shared id. But in some instances where I can see that the two polygons are touching I'm not getting an id created between these two.

Would anyone have any idea why this is happening? I can share any details through screenshots, just ask.

Thanks for any help.

B

11 replies

ebygomm
Influencer
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  • ebygommInfluencer
  • Influencer
  • November 20, 2020

Are you sure the polygons actually touch? I imagine that there can be a very small gap between polygons and as the spatial relator has no tolerance it will report as not touching.

The dissolver has a tolerance setting so it will dissolve polygons that the spatial relator reports as non-touching

bjudes
Enthusiast
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  • bjudesEnthusiast
  • Author
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  • November 20, 2020
ebygomm wrote:

Are you sure the polygons actually touch? I imagine that there can be a very small gap between polygons and as the spatial relator has no tolerance it will report as not touching.

The dissolver has a tolerance setting so it will dissolve polygons that the spatial relator reports as non-touching

Thanks for the reply.

 

Yes, they are definitely touching. I even went as far as buffering the polygons to be dissolved by a very small amount, just to be sure they were touching. It still didn't change the outcome.

ebygomm
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  • ebygommInfluencer
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  • November 20, 2020
bjudes wrote:

Thanks for the reply.

 

Yes, they are definitely touching. I even went as far as buffering the polygons to be dissolved by a very small amount, just to be sure they were touching. It still didn't change the outcome.

Have you checked they are valid geometries?

M
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  • markatsafe
  • November 20, 2020
ebygomm wrote:

Are you sure the polygons actually touch? I imagine that there can be a very small gap between polygons and as the spatial relator has no tolerance it will report as not touching.

The dissolver has a tolerance setting so it will dissolve polygons that the spatial relator reports as non-touching

@bjudes​  Can you attach a small sample of the data? Members of the community could then experiment and see what might be causing the problem

hkingsbury
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  • hkingsburyCelebrity
  • Celebrity
  • November 22, 2020

Just checking that they're in the same projection system?

bjudes
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  • bjudesEnthusiast
  • Author
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  • November 23, 2020
markatsafe wrote:

@bjudes​  Can you attach a small sample of the data? Members of the community could then experiment and see what might be causing the problem

Hi @Mark Stoakes​ @ebygomm​ @hkingsbury​ Thanks for the reply. I've attached a sample of the data. The polygon I want to dissolve/relate to its neighbour is OBJECTID 1494. Let me know if you have any questions and thanks very much for the help.

B

1 Attachments
bjudes
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  • bjudesEnthusiast
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  • November 23, 2020
hkingsbury wrote:

Just checking that they're in the same projection system?

Hi,

Yes, everything is in the same projection, thanks for the reply.

B

bjudes
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  • bjudesEnthusiast
  • Author
  • Enthusiast
  • November 23, 2020
bjudes wrote:

Thanks for the reply.

 

Yes, they are definitely touching. I even went as far as buffering the polygons to be dissolved by a very small amount, just to be sure they were touching. It still didn't change the outcome.

I placed a geometry validator before the said spatial relator process takes place and it still does not work. The geometry also looks fine to view. Please see the sample I attached above, if you have time. Thanks

B

ebygomm
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  • ebygommInfluencer
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  • November 23, 2020
markatsafe wrote:

@bjudes​  Can you attach a small sample of the data? Members of the community could then experiment and see what might be causing the problem

The spatial relator reports that polygon with OBJECTID 1494 touches 5 others for me

Capture 

bjudes
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  • bjudesEnthusiast
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  • November 23, 2020
markatsafe wrote:

@bjudes​  Can you attach a small sample of the data? Members of the community could then experiment and see what might be causing the problem

First a note, I'm running on 2018.1 and due to a bug in the latest version I need to run this version. The first image below shows the name I gave the relationship (_relationship_DES) and the second shows that there is no relation between my polygon 1494 and the surrounding ones. I have some other caveat, it needs to group by GUID, but there are a number of polygons in the vicinity with the same GUID, there are also 399 other polygons going through to be related, but almost all of these correctly relate to their neighbouring polygon.

DESDES2Thanks

B

M
Forum|alt.badge.img+2
  • markatsafe
  • November 23, 2020

@bjudes​ I can't reproduce in FME 2018.1. For OBJECTID = 1494 I see:

2020-11-23_14-23-05Can you include your workspace, or better yet a small sample workspace that reproduces your isse. What Spatial Predicate are you using?

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