Generate Point Layer at Line Intersection

Question

I have a line layer that is actually buffer polygons converted to a line layer. I would like to generate points at all places where 3 or more lines intersect. I would settle for places where 2 or more lines intersect. I know that this is possible to do if all the lines were different layers. What I need is a method to do this when all the lines are contained in a single shapefile. There are too many lines to separate them into individual files.

• ArMoraer: Related post if you're open to scripting: Intersecting lines get crossings
• Kingfisher: I'll take a look, though scripting is not my forte.

Answer 1

You could do it in three (or four) steps:

(1) Create nodes at intersections

Processing Toolbox | GRASS | Vector | v.clean and select break option.

(2) Extract nodes as points layer.

Processing Toolbox | QGIS geoalgorithms | Vector geomerty tools | Extract nodes

(3) Only keep duplicated points (Nodes)

1. Open attribute table of Nodes (output of Extract nodes tool)
2. Give an expression: count( "id", group_by:= geom_to_wkt($geometry)) ...assuming you have an id field.
3. Remove features whose count is only 1 (one).

(4: optional) Remove duplicates (e.g. Delete duplicate geometries tool...)

Answer 2

Yes, use the line intersections tool from the Vector drop-down menu. Choose Analysis Tools and then Line Intersections.

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• Louis: This is an answer for separate shapefiles, I don't think this tool works for intersections within the same shapefile.
• Kingfisher: Yes this won't work for me since the lines are all in the same file.