I have a set of road conditions reported for small segments of road, and I am hoping to determine the specific subset of each segment which intersect with a route along the road so that I can draw the intersection of the route and road conditions on a map.

Is there a way to determine the specific points of intersection of two polylines in PostGIS in a way suitable for plotting on a Google Map?

I am new to PostGIS so please accept my apologize if I am getting any terminology wrong.

1 Answer 1


St_Intersection function will give you the a point/collection of points that are the intersection of two linestrings. ST_Intersects can be used to find linestrings that intersect.

  • Thanks! I'll give that function a try once I've got my data loaded in. Is there a tolerance when a point is considered "close enough" to overlap or do the points need to be identical to match?
    – Mark B
    Jul 8, 2013 at 15:45
  • 1
    There is no tolerance, you can use ST_Buffer to make the lines "thicker" but then you'd have to choose what point you want to represent the intersection. Jul 8, 2013 at 17:53

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