Question

FME Desktop 2022: The “clip” tool fails to produce the expected result,

  • 27 February 2022
  • 10 replies
  • 26 views

Badge +5

FME Desktop 2022: The “clip” tool fails to produce the expected result,

 

In the screenshot below, I wanted to clip 14 polygons from 1 polygon (the 14 polygons are contained in the 1 polygon). The expected result should be one polygon that represents all what is outside the 14 polygons. However, the clip result is shown in the 3rd screenshot

 

What could be the issue here?

 

The data and workbench are attached

 

Clip_119 

Clip_120Clip_121 

 

 

 

 

 

 


10 replies

Userlevel 5
Badge +29

Add a dissolver and aggregator to the clippers. I think you may have geometry issues with your input data.

 

Generally i wouldn't expect to have to do the dissolve/aggregate and your inital approach should've worked fine

Badge +5

I erased one of the polygons that has issues at the level of AutoCAD. However, the issue persists to exist despite the fact that the “geometry validator” tool detects nothing

 

Which geometry issues in need to resolve so that the result gets correct?

 

Why the “geometry validator” tool fails to detect any issues while the result of the “clip” tool is incorrect?

 

The data and workbench are attached

 

 

Clip_128 

Clip_129 

Clip_130 

 

 

 

 

 

 

 

 

 

 

 

Userlevel 5
Badge +29

I erased one of the polygons that has issues at the level of AutoCAD. However, the issue persists to exist despite the fact that the “geometry validator” tool detects nothing

 

Which geometry issues in need to resolve so that the result gets correct?

 

Why the “geometry validator” tool fails to detect any issues while the result of the “clip” tool is incorrect?

 

The data and workbench are attached

 

 

Clip_128 

Clip_129 

Clip_130 

 

 

 

 

 

 

 

 

 

 

 

If there's no geom errors than thats fine, I was just wondering if there might've been some issues that would cause this

Badge +5

Really weird. How come the result of clipping 13 polygons from 1 polygon can be as shown in the screen considering that fact that there are no geometric errors?

 

Clip_175 

Clip_176 

 

Clip_177 

 

 

Badge +5

This should be a bug!

 

I managed to get the result of testers and stick it in a file geodatabase, then I did the analysis in Pro. The result is as expected

 

Clip_180 

Clip_178 

Clip_179 

 

 

 

 

 

 

 

Badge +11

Hi @jamal​ ,

I think there is no bug involved on any transformer. The problem is coming from the INPUT data (which polygon coordinates has less precision than expected).

The fact that you then used a FileGDB to perform an ArcGIS Pro operation is not that a proof that something is happening in FME Desktop. What I mean is that the FileGDB interacts with your geometry and "implement" a snapping grid which modify the INPUT coordinates, luckily, it solves directly the precision issue that comes from the INPUT.

So, FME uses all the precision from your input, which ends up failing or giving you a bad output when performing complex spatial transformations. And once again, it does not mean that FME is now working well, is because is trying to do some spatial operations where topology must be fine in case you want to have a successful result.

There is a Transformer called Snapper, which acts likely FileGDB format is doing. For that reason, from your input, when polygon shared coordinates are too near, but not the same X,Y, we're forcing with this transformer to be the same, to be totally aligned. With that, you can continue with the rest of Spatial transformations without any issue.

Here is the Workbench that I've re-used from the one you uploaded:

workbenchOn this case, I've used AreaOnAreaOverlayer instead of Clipper (which I guess could produce same output).

Here is the Output:

 

1_ Inputs:

14 polygons1 Polygon2_Final:

Output

Let me know if you have any doubts,

Juanma

Badge +5

Thank you very much for the amazing input.

1) I couldn't know what to choose for the snapper tool

2) As i apply the "PointOnAreaOverlay" tool i got it not worked as yours

 

could you please share the workbench?

 

Clip_215 

Clip_216 

 

 

 

 

 

 

 

Badge +11

Thank you very much for the amazing input.

1) I couldn't know what to choose for the snapper tool

2) As i apply the "PointOnAreaOverlay" tool i got it not worked as yours

 

could you please share the workbench?

 

Clip_215 

Clip_216 

 

 

 

 

 

 

 

Sure, here is the workbench attached. "Simple_solved.fmw".

 

Regarding the Snapper parameter, you'd need to adjust to your Reference system values, and to know "how much" your polygons are misplaced one to the other.

If you still find any issues, feel free to comment ;)

Best,

Juanma,

Badge +5

Thank you juanmahere for the prompt help.

 

How to IDENTIFY (but not to resolve) the polygons (and their vertices) that have snapping issues which resulted in having the clip not to work as expected?

 

Clip_22

Badge +5

I’m still struggling in how to IDENTIFY polygons that have this issue and what this issue is all about that causes not to get the expected result from the clipper

 

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