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I'm currently in a project where I need to identify whether the road exist in an intersection or not. However there are 700 roads which is a hassle if I do it manually. Is it possible to identify whether the road intersects or not through QGIS commands?

enter image description here

enter image description here

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  • 5
    Can you add a screenshot showing your data and what you want to identify?
    – BERA
    Jan 13 at 6:32
  • 1
    What about bridges or underpasses? Lines visually cross, but are not connected topologically
    – Babel
    Jan 13 at 7:33
  • Can you draw some arrows showing what and what not to identify in your screenshot
    – BERA
    Jan 14 at 7:26
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Solution 1

Run Menu Processing / Toolbox / Line Intersections (see documentation) to get a new layer with points showing where lines cross (red dots in the screenshot). You can select twice the same layer as Input and and Intersect layer or two different layers, depending which intersections you're looking for.

Solution 2

Create line intersections with Geometry generator for visualization only (yellow stars in the screenshot) with this expression:

collect_geometries(
    array_foreach(
        overlay_crosses( 
            @layer, 
            $geometry
        ),
        intersection (
            $geometry, 
            @element
        )
    )
)

If you want to get the intersection points of two line layers, replace @layer in line 4 with the name of the other layer in single quotes: 'other_layername'.

Both solutions demonstrated with intersection from the same layer: enter image description here

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  • Hello, thank you for this. I edited my question to post some pictures of my work. Is there any ways to reflect in the attribute table whether the roads intersects. My tasks involves in identifying whether the roads intersects or not. If it intersects then True (T), if not then False (F). I've been doing it manually for some roads. Jan 14 at 3:09
  • 1
    Just use overlay_crosses( @layer )
    – Babel
    Jan 14 at 7:07

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