I got a dataset of streets, which are displayed as line segments. In another, independent dateset I have roundabouts as a point geometry.

Starting from these datasets, I want to count the number of streets which lead to the roundabouts. I would start to make a buffer around the point-geometry of the roundabouts and afterwards intersect the buffer-polygon with the streets.

But how can I count the number of streets, which intersect with the buffer?

QGIS 2.6.0

  • Welcome to GIS:SE Peter! Are you asking how many streets intersect each buffer or how many streets in total are intersecting a buffer?
    – Joseph
    Mar 24 '15 at 11:02
  • Could you, as you suggested, intersect the buffers with the streets, then use the Vector > Geometry Tools > Extract Nodes tool to convert your lines to points where they were split by the intersect tool - then use the buffers to select those nodes, and count them up? Mar 24 '15 at 21:05
  • Not sure if you can do it this way in QGIS (see gis.stackexchange.com/questions/120229/… for why), but in Arc I'd look at a spatial join (lines joined to points) with the one-to-many parameter. That would give you a count of how many lines intersect the roundabout point. The same method would also apply to your lines and buffer polygons. Alternatively you may be able to Intersect the two layers and it would create a duplicate point for each road that touched the point, then count the number of points.
    – Chris W
    Mar 24 '15 at 22:41
  • Couldn´t you simply select the streests that intersect your roundabouts? Oct 26 '15 at 13:11

I wanted to count the number of street intersections with the border of one buffer.

My solution:

  1. Calculate buffer
  2. Change border of buffer to line (Vektor - Geometry Tools - Polygons to Lines).
  3. Calculate line intersections (Vector - Analysis Tools - Line intersections)
  4. Count intersections.
  • 1
    If this solved your problem you can also accept your own answer as the correct one with the little grey/green tick mark on the left.
    – Kersten
    Oct 26 '15 at 10:25

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