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I’ve simplified some GeoJSON data to use on a Garmin device, however the simplification affected junctions and interchanges, which created some undesired shapes, unfortunately no attributes were provided in the original data to determine junctions and interchanges from regular road. Currently the red shapes form part of the black lines, I’d ideally like to separate them from the black lines then remove them to clean up the data. The data is large so I’d like to find a way to do this automatically.

Red = shapes to be removed, green = connections to be added when red shapes are removed

Red = shapes to be removed, green = connections to be added when red shapes are removed

Original data: https://www.globio.info/download-grip-dataset

(Note that the original data is in shapefile but I converted it to GeoJSON in QGIS).

In response to a recent query: The coordinates of the image is (50.8687089, -0.1521607). I simplified with I believe 0.003 tolerance and the visvalingam option? I also tried it in mapshaper as well (visvalingam too) and that was about 10% on the simplification slider using the second option of the two different visvalingam methods.

I should also add that I removed local roads from the original data as that significantly slowed down the draw time and to reduce file size.

IceBear123
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  • Could you share the original data? – GforGIS Mar 25 '24 at 02:07
  • @GforGIS I have updated the post to provide a link to the original data, it is specifically the Europe region. – IceBear123 Mar 27 '24 at 12:01
  • Exactly what processing steps did you execute in QGIS, and which settings did you set in for example simplify? What is the coordinates of the screenshot you are showing – BERA Mar 27 '24 at 18:29
  • @BERA I have provided the requested information to the best of my memory. – IceBear123 Mar 29 '24 at 19:56
  • Writing code to handle these case is probably way slower than just changing the generalization rules, but doing either is not a trivial task. – Vince Mar 29 '24 at 20:12
  • I dont get the red lines you get when simplifying. But the topology is ruined. Maybe you can try this? – BERA Mar 30 '24 at 07:43
  • Thanks BERA, I will try this when I get my new computer setup, if it works I’ll confirm it as an answer. – IceBear123 Mar 31 '24 at 16:36

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