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.

enter image description here

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?

enter image description here

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


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

enter image description here

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

enter image description here

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

enter image description here

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

enter image description here

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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.