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I've cleaned up a road network so that I can use the shortest path tool, but some intersections don't have a vertex on one/both roads, so the result ignores this intersection.

How can I split or insert a vertex on one line where it meets another line, whether at a T-intersection or road crossing?

I've tried extending, splitting, etc. but nothing works.

  • v.clean with break tool to create node. As to T-intersection, it is probably better to do v.clean- snap beforehand to make sure lines are met at the point. – Kazuhito Nov 27 '17 at 1:31
  • Also be aware that sometime road can cross without it being an intersection (like with tunnel or overpass), in these case you should not add vertex – J.R Nov 27 '17 at 12:14
  • True. We only have this with the freeway which we can edit afterwards. – Joshua J Geoghegan Nov 29 '17 at 22:20
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In QGIS Processing Toolbox, there is a GRASS command v.clean (GRASS | Vector | v.clean) which, with break tool, can add vertex (node) to lines at each intersection.

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When we have T-intersection, it does not create node unless the intersecting point is located exactly on the line. (An example is shown at the right hand side of the picture).

To make sure these lines meet at the intersection, v.clean snap tool can be helpful. This snap tool is usually used before break tool.

enter image description here

As a negative side, this operation can bend lines, trying to snap them together... please use it carefully.

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