I am trying to use the SAGA "Split lines at points" tool within QGIS. I first had a polyline layer with line segments/features of arbitrary length. I then did the following:

  • Dissolve using the native QGIS dissolve tool.
  • Created points at equal length intervals along the dissolved layer using the native QGIS "Points along lines tool"
  • Tried to split the polyline layer using the "Split lines at points tool".

The resulting polyline layer is strange. While it does split the polyline layer at the point locations, it also retrieves the segmentations which were existing before in the original polyline layer. Here's an image where one of these "rogue" segments is selected and where I show what I mean:

enter image description here

Before dissolving and splitting the line layer this is what the segment looked like:

enter image description here

Why does the old segmentation come back? It seems like "Dissolve" doesn't dissolve the underlying geometry sufficiently so that SAGA knows to ignore the old segments...

  • Try running "merge lines" on the dissolved layer - that will attempt to convert multiline features to single line features by merging touching lines – ndawson Sep 17 '18 at 9:40

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