qgis
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.
You can find multiple versions of routing scripts which use the QGIS network analysis library in my Github repository, e.g. https://github.com/anitagraser/QGIS-Processing-tools/blob/master/2.2/scripts/point_layer_to_route.py which converts an ordered set of points into a route.
None of the scripts use the intersections of an input line with the network. That's something you will have to add on your own.
Use the "Split with lines" tool from the Processing Toolbox (Ctrl+Alt+T).
You can use "Split lines with lines tool" in QGIS from Vector overlay Tools > Split lines with lines to add node when two lines get connected together. The input line file can be the same file for input layer and split layer, as you can see below:
After running the "Split lines with lines" tool and use same file for input layer and split layer, as you can see below:
The output will be like this:
The "Split lines with lines" tool can be found in the Processing Toolbox:
Best Answer
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.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.cleansnap tool can be helpful. This snap tool is usually used before break tool.As a negative side, this operation can bend lines, trying to snap them together... please use it carefully.