Dissolve overlapping polygons in SAGA
I've got the following (2D!) situation of overlapping polygons:
I would like to have the polygon border dissolved such that I have only one polygon left. I thought this was a definitive case for the dissolve tool, but somehow the result is bizarre:
What did I do wrong? I haven't chosen the attribute to dissolve on so I thought then all polygons are dissolved and should bring the desired result. Can anybody help?
EDIT: A clipped version of the data can be found here:
I too encountered the bug, here's a workaround:
- Do the Merge without the "keep boundaries" that returns the weird result.
- Split you source data to individual features
- Perform Intersect on the 2 resulting layers
- merge the result of the dissolve with the result of the intersect
- Final dissolve to create required layer
If you need to save attributes of the original data, make sure you retain the fields you need during dissolve operations
Try it with the keep boundaries box un-ticked. I am assuming that you are using the polygon dissolve field.
Okay, so here's one workaround I received from SAGA's developer Olaf Conrad, personally:
He said that overlapping polygons are actually not "allowed" as input for the dissolve tool and SAGA assumes that all polygons layers are "clean" (=without overlaps).
His idea is to
1) Use 'Polygon self-intersection' to get the overlaps as polygons, too
2) Use 'Dissolve' to get the desired result.