dissolvegrassqgisunionvector
I have 4 vector shapefile that I would like to join/merge, without worrying about attributes.
Here are the shapefiles.
I would like to do an union and a spatial dissolve, but everytime I do a dissolve after "PUP" and "PRG" layers union, I got an error about wrong geometries and the output layer is empty.
I validated layers geometry with no errors (at least is what QGIS tells me).
Am I missing out something?
After hours of trial and error, I found a solution that I answered here: How to merge and dissolve adjacent polygons and sum up their attributes in QGIS?
Another solution that may be used particularly in the Processing Modeler.
Let's assume there are two polygon layers 'layer_1' and 'layer_2' with its corresponding attribute tables accordingly, see image below.
With the following model, it is possible to merge two vector layers with no attributes only their geometries.
The output with its Attribute table will look as following
Note:
On the last image, attributes were added by default
For both SQL queries use these settings
Best Answer
While doing spatial joins in QGIS you have to make sure that all your layers are in the same projection! Otherwise there is a high chance of wrong outputs.
In your example data the shapes PUP and PRG have no correct set CRS projection, while the other shapes are all in ETRS89/ETRS-TM32.
-> Reproject them by saving them with the correct CRS (right-click on layer -> save as with selected ETRS89/ETRS-TM32 projection). -> Then load in the reprojected layers and merge them via the mmqgis function merge layers or through the function in the QGIS vector menu.
As soon as you have one single shape, you'll find the dissolve function in the vector menu.