I have several large shapefiles from various sources. All cover various sections of oceans and many overlaps, as such the coastline is repeated across the several shapefiles but to varying levels of details/accuracy.

The outcome I would like to achieve is one shapefile, with one coastline.

I can merge the shapefiles in QGIS but how would I align the coastline and drop its duplication?

  • 2
    Maybe it can be done with Differences and Unions. Also, you can try the snap tool of GRASS v.clean algorithm. The solution to your problem will be more or less handmade and specific according to your source data. Dec 7, 2019 at 22:26

1 Answer 1


You can use Menu Processing / Toolbox / Merge vector layers and set all the layers you want to merge. See the result:

enter image description here

Now you can dissolve the output layer: Menu Vector / Geoprocessing Tools / Dissolve and you get the maximal extenstion of all features in the output, see:

enter image description here

  • Thank you so much for this, looks like it should do the trick but i'll get back to you once QGIS is done processing. Thanks again Jan 18, 2021 at 6:59

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