Splitting ring polygon using QGIS?

Question

I have ring polygon (I'm filling GAP between parcel by INDEX4000). I'm trying to use split feature to split (cut) the ring polygon into road and water, but it does not work. Any ideas?

Answer 1

Since you have only one polygon (the yellow part as I see), I think it is impossible to split it automatically in various themes (in your case road and water). You will have to split your polygon manually. You have to ...

1. Right click somewhere in your toolbars and turn on 'advanced digitizing'

1. Make your layer editable (The Button with the yellow pen)

2. The 'Advanced digitizing' Toolbar becomes active, you can see two icons with scissors:

3. With these you can simply draw (indeed very complex) lines a), where you want to split your polygon. Right-click then splits the polygon (I translated the parts a bit for better explanation) b):

a)

b)

Having done so, I would create new Layers for each water and road and then copy the polygon parts to these layers. Alternatively you may add an attribute e.g. 'category' before you split the polygon, and after the split select all water parts and set the latter attribut value to 'water' and so on.