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Assistance needed converting Lines to Polygons Using AreaBuilder


nstem
Participant
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Good afternoon, I am extremely new to FME so apologies in advance if my question comes across as exceedingly simple or unnecessary. Anyways, I am attempting to convert a set of line features that originated in AutoCAD into a GIS formatted polygon layer. To start, I cleaned the layer as best as I could and performed snapping within QGIS. I then have tried using AreaBuilder in combination with other transformers such as LineCloser to obtain a set of polygons, but the output so far has been less than ideal. I have also experimented with Snapper and some other transformers such as LineExtender but those have introduced new errors that then lead to no output from AreaBuilder. Below I have attached an image of my workspace currently, as well as an image of the current output I am receiving. I will also attach a sample of the dataset I am working from! My conclusions are that LineCloser is causing the issue which leads to these slivers and polygons outside of the scope of the data, however I am not sure where to begin fixing it currently. I know I am most likely going to need many more transformers to accomplish this task, but I am at loss on where to start/what order to put said transformers in. Any assistance or guidance would be greatly appreciated. Thanks!

 

3 replies

DanAtSafe
Safer
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  • Safer
  • June 30, 2025

Hi ​@nstem There are gaps in your lines which are best solved by a Snapper (with segment snapping).

The LineCloser will add a segment between the first and last vertices of a single line.  Also, your units are decimal degrees so ideally you could reproject your data to a local coordinate system when dealing with topological issues.  I’ve put a TopologyBuilder in my workspace to check for dangling nodes.


takashi
Evangelist
  • July 1, 2025

Hi ​@nstem ,

I tried using Intersector instead of TopologyBuilder, and got a bit different result as shown below.

In my observation, there are some collinear edges in the resulting edges by the TopologyBuilder whereas the Intersector removes those collinear edges by default. I think this is the reason for the difference.

@DanAtSafe , could you please check this? 


DanAtSafe
Safer
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  • Safer
  • July 1, 2025

@takashi The TopologyBuilder seems to copy and reverse all edges and some aren’t getting cleaned up.  I’ve filed FMEENGINE-87258 about this.


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