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I have a stream network and I want to find the red points as shown below.

enter image description here

I have tried using Q-chainage and Line Intersection feature in QGIS but it gives more than expected number of points. The red points 513 and 556 are expected intersection points of stream segment and point 518 is expected start/end point, but the rest points are not required.These extra points may occur because the poly line representing each stream segments is broken into multiple line segments represented by intermediate points which is expected to be single geometry in ideal case.

So, I have also tried merging the poly-lines based on "value" attribute (in PosgreSQL by ST_Union ) as it had common value for most of the stream segments. But then in some cases still the split of poly-line is not for each stream segment but spans out to other stream segments as well.

Please also point out if there are errors in pre-processing of data. I have generated the stream network from DEM with and without eliminating the depressions using r.fill.dir in QGIS . Is there any other processing required? If not, please point out a method to find only start,end and intersection points in the given network.

  • I have performed stream.order from grass which takes care of the above issue. – Swapnil Jun 20 at 14:01

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