I'm curious if anyone can explain the strange effects I'm seeing from the SAGA 'Line Dissolve' tool. I have a ton of line features that had previously been 'exploded' (which is a necessary step), and now need to be rejoined together so that 'Create Points Along Lines' works properly.

Using the Vector > Geoprocessing > Dissolve tool takes an ungodly amount of time to process (I'm talking hours for a single dataset, which is much too long), but creates expected results after adding the points along the dissolved lines. When I run the 'Line Dissolve' tool from the processing toolbox, it takes about 5 seconds to process, but the points along the lines are sporadic and seemingly placed at random (see attached screenshots).

Points along lines after Vector > Geoprocessing > Dissolve: enter image description here

Points along lines after "Line Dissolve": enter image description here

  • When joining the lines with Dissolve, are you using a Field to identify which lines should be joined together? – klewis Nov 30 '16 at 20:37
  • @klewis yes, using the field 'DN', of which all lines have the same value (255) – GIS_Canuck Nov 30 '16 at 20:42
  • After Dissolve, do you have a single multi-part line? – klewis Nov 30 '16 at 20:45
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    Are you confident the lines don't repeat back on themselves? I've seen this before when the line switches direction. – Fezter Aug 10 '18 at 0:42
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    see my answer to this question - as per @Fezter suggestion. This clumping can be due to direction switches between successive segments. – Steven Kay Aug 10 '18 at 17:35

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