[GIS] How to overlap and merge layers in QGIS

layersmergeoverlapping-featuresqgis

I have two layers (1 and 2) and I want to overlap them and the intersection and the union didn't work.

I want to get something like this:

Is it really easy or is there a special method to follow ?

I am working with QGIS.

Best Answer

First use 'Symetrical Difference' instead of 'Intersection' in the Geoprocessing toolbox and then in a second step do 'Union'.
The yellow triangle in 2. is spatially in the same location as in 1. yet I didn't knew how to illustrate it in a better way. I hope you get what I mean.
That should do the same thing and didn't raised any errors for me (QGIS 2.18.0 on MacOS 10.11.6)

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I guess a Memory Provider would suite your needs as

It does not store data on disk, allowing developers to use it as a fast backend for some temporary layers.

Based on your descriptions and the linked example from the cookbook I created some code. It is not fully tested and maybe you will have to tweak it a little:

lyrs = self.iface.legendInterface().layers()

fields = lyrs[1].pendingFields()

vl = QgsVectorLayer("LineString", "temporary_lines", "memory")
pr = vl.dataProvider()

for f in fields:
  pr.addAttributes([f])

vl.updateFields()

feats1 = lyr[1].getFeatures()
for feature in feats1:
  pr.addFeatures([feature])

feats3 = lyr[3].getFeatures()
for feature in feats3:
  pr.addFeatures([feature])

vl.updateExtents()

# Do something with it

Best Answer

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