Create Centrelines of polygons
Hi,
I have been sent a road network in polygon shp file format and need to translate this to just the centreline of each polygon. This will show the road network as a polyline instead of a polygon. Please note I am not just looking to turn the polygons into polylines.
Any help would be most appreciated.
One way would be to do following.
1. Negative buffer then a generalizer in reduce mode. Then densify and smooth.
2. Remove pieces smaller then a certain length (like halve average road widht or so).
If visualy not satisfying. You can do step 1 in succesion.
You'll never get a exact centerline network (unless u live in a square grid city or something) without manual labour.
Hi Amilu,
Does the following list of transformers does the job with sufficient accuracy?
CenterLineReplacer > HullReplacer (Concave) > CenterLineReplacer
I think this will work OK if the 'hair' on your line is not too long.
Just a little tip, if you have lines that are curved, you might want to make use of the concave-option in the HullReplacer
Converting polygons to their centrelines is surprisingly difficult and I have had issues before. The centrelinereplacer does a pretty good job but it has limitations.
By hairy line do you mean the tributary lines coming off the main road? Or are you referring to the smoothness of the actual lines? You could use the generalizer to smooth the output. If you are referring to the tributaries you could use a chopper or an intersector to split the lines apart, then filter out the ones you need.
Hi
Have a look at the CenterLineReplacer
David
Hi,
I have tried CenterLineReplacer and it produces a "hairy" line.
I have only used 1 polygon at the moment to test this on. Any other ideas?
Thank you in advance.
Can you post a screenshot of the polygon that produces the hairy line? I'd like to see what that looks like for FME to produce something like that.
I tried it on a dataset and did get occasional 'hairs' but only at the end of lines. Perhaps you are working on multiple polygons? Can you dissolve them together with the Dissolver?
