I am trying to figure out the best solution to hide overlapping lines. I have a layer of polygons representing crustal plates. I have a polyline layer of fault lines that overlap some of the polygon boundaries. The fault lines are represented by dotted lines and the polygon boundaries which have solid lines are showing through the dotted lines.

How can I make the boundary lines not show through the polylines?

Currently I can either turn off the borders on the polygons which causes additional problems or I can offset the polylines which is not an accurate representation of the line.

There doesn't seem to be a solution that satisfies my client entirely. Basically the image shows a similar situation. The two blue polygons are bordered in white and the fault line in dotted black which he doesn't want to have white behind. Basically he wants to have no border where there is a dotted line which is impossible. My advise to him is to either remove the borders all together or live with the overlap. enter image description here

  • I'm not able to comment on your answer, yet, however, if the polygons are monochromatic like your image shows, then making by the mask line the same color blue, it will disappear except where there is a border. Dec 2, 2015 at 18:12
  • The problem is 90% of the lines overlap the borders completely. Its completely an aesthetic issue and silly but its just bugging my OCD to the max. Dec 2, 2015 at 18:34
  • Believe me, I feel your pain. Dec 2, 2015 at 18:47
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    I know it could mean a lot of work but the other alternative is to change your polygons into lines and cut out all areas that overlap with your dotted line feature. BTW did setting a symbology representation not work?
    – yanes
    Dec 2, 2015 at 18:52

3 Answers 3


The answer is in your question.

  1. Convert polygons to lines (features to lines)
  2. Merge them with fault line
  3. Dissolve output from step 2 into single part polylines
  4. Select and delete from DISSOLVED lines that share line segment with FAULT line


enter image description hereenter image description here

NOTE solution applicable for topologically correct geometries, i.e. fault lines truly follow boundaries and there are no slivers/overlaps in polygon layer.

Some manual editing possible, consider fault line going up a bit from uppermost point.


The symbology representation setting works when both lines are dotted. I am not sure if it works for a dotted and solid line overlap but it is worth a try. Here is my answer for a similar question.

If the above doesn't work, You can convert your polygon features into line feature using feature to line tool and then use the erase function to remove all the areas the newly converted lines intersect with your dotted line feature. then use that instead of the polygon feature in your maps.

  • 1
    +1 didn't read your solution to the end, thus posted my one
    – FelixIP
    Dec 2, 2015 at 19:34
  • I like your version, it is well illustrated. will be useful for other users too! I was in a hurry, I couldn't include a step-by-step :)
    – yanes
    Dec 2, 2015 at 19:35

An alternate way to do it would be just to draw the fault lines twice, once as dotted lines, and once as a smooth solid line using two different layers. Then, set the transparency of the solid line to 40% or so, so it's just enough to highlight the dotted line.

enter image description here

  • To make things more complicated... The symbology of the fault lines cannot change (set by a standards manual). One of the features is a wide dotted solid black line, another a thin dashed line. The symbology of the background polygons is not set in stone though. My gut move is to use a light light gray polygon boundary and hope that the line isn't noticeably interfering with the polyline symbology. Dec 2, 2015 at 17:22
  • In that case, I would definitely go with drawing the semi transparent mask line behind the dotted line. Maybe up the transparency a little. It won't really look like you changed the line symbol, rather it will just look like your line is backlit a little bit and a some of the underlying map will still show through. But it will be more defined and less messy. Make the mask a bit wider than the standard line symbol. Dec 2, 2015 at 17:38
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    Not sure if we can put links here but it might look something like this: i.imgur.com/wINWJPh.jpg Imgur Dec 2, 2015 at 17:54

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