I have a shapefile for a country and a shapefile representing the mobile network coverage of an operator in that country. I would like to create a shapefile that represents the parts of the country not covered by the mobile operator. I tried Symmetrical Difference which worked around the edges but that did not get at the internal gaps in the network coverage map.

  • Several different geoprocessing overlay tools could achieve this outcome, including Union (with suitable extraction by attribute) and a simple Erase. – Vince Jan 16 '17 at 18:12

You may try using the Symmetrical Difference SAGA tool from Processing: In the past I encountered some problems with the in-built algorithm, so you may do another attempt.

Before running the algorithm, make sure to activate the Processing Toolbox going to Processing > Toolbox and then type Symmetrical difference in the search bar for quickly finding the algorithm:

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It will work as the Symmetrical Difference tool which is in the core of QGIS:

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  • I was hoping for a solution in QGIS but this worked for me. Thanks! Curious to know why Symmetrical Difference worked in SAGA but not QGIS. – SteveSong Jan 17 '17 at 17:56
  • Sincerely, I don't know why: probably, some problems may arise in QGIS when the difference operation is done over more than two intersecting features. However, I'm glad it worked for you! – mgri Jan 17 '17 at 18:05
  • Short follow-up. Discovered I can run the SAGA Symmetrical Difference function successfully from within QGIS – SteveSong Jan 20 '17 at 14:33
  • You mean outside the Processing Toolbox? – mgri Jan 20 '17 at 14:38
  • No, I misunderstood your original suggestion and installed the SAGA GUI and used that initially. – SteveSong Jan 20 '17 at 19:42

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