Split a large polygon with a layer of polylines or with a layer of polygons

Question

I have a large polygon, of about a size of a municipality and i want to split it in about 12 - 13 pieces by using a related layer of either polylines or polygons (buffered polylines).

I tried using the Digitizing tools plugin but without success. I merge all the polylines or all the buffered polylines in order to have one feature that will be used to cut my municipality-polygon but it just does not work, without even have an error message. It just loads for a sec and then the municipality - polygon in still the same.

I also tried the erase function (difference) but i do now know if there is a way to split it after it is clipped.

Answer 1

To split a polygon with lines, use the Split with Lines tool. This tool is available in the processing toolbox.

Lines and polygons before splitting:

Split with Lines Tool Settings:

New Split layer created by tool:

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To split a polygon with buffered lines (i.e. another polygon layer), use the Union tool. First, add a field to the polygon layer called "source layer". Type 'polygon layer' into that field for every polygon.

Buffered lines and polygon before splitting:

Union tool settings:

Union tool output (contains features from both input layers):

Open the attribute table for the Union layer. Select and delete all features that have null values for "source layer."

Answer 2

You could use symmetrical difference to cut the polygons and buffered polylines out of your municipality polygon And then copy and paste them back into your new symmetrical difference layer.

Answer 3

You could use the "Feature to Polygon" tool. The input would be both the municipality and the shapefile of what you want the municipality subdivided by.