1

I am trying to find digitizing errors in a line-layer. Obviously the snapping was not activated when the person who digitized created the lines.

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As far as I know QGIS cannot find undershoots, so I try to find close vertices. OpenJump has a tool called "Find Close Vertices" which helps finding some of the digitizing-errors. How could I archieve something like this in QGIS?

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I tried to use v.clean with the break option to find the errors but this did not help much.

Test-data can be found here: https://gist.github.com/rdbath/104876de54fdfe0fc3ceed521220673e?short_path=f75c9b4

3

Usually GRASS v.clean - Snap option does a great job, setting the Threshold (in your case 0.2 meters) to cover the gap.

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However, the result is not ideal. Lower branch was snapped up onto the upper branch, not to the right one.

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A workaround is to (1) Snap with small tolerance to fill the small gap first, then (2) Snap again with larger tolerance to fill the larger gap.

(1) First snap by Threshold = 0.1

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(2) Second snap (the Cleaned red line layer from the above is the input) by Threshold = 0.25

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The new blue Cleaned line is the final output.

  • Thanks for this interesting idea. However I would prefer a solution which only detects "errors". The lines belong to a fibre-network planning and automatically snapped lines could result in wrong connections (unfortunally the distance of the gaps vary quite much in other datasets, so finding the right thresholds could be a game of luck). – markgraeflerland Dec 11 '18 at 7:04

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