Create two new polygons inside existing polygon hole

Question

I would like to create new polygon inside the existing polygon. It does not means donuts polygon.

I would like to have two polygon without overlapping.

I can create if I don't check "Avoid intersection" from snapping option. Unfortunately, there is overlapping new polygon and existing polygon.

It must not have overlapping area.

Answer 1

There are two ways to do it in my mind. If you have many complicated polygons:

1. create layer with outer polygons
2. create layer with inner polygons
3. use Vector / Geoprocessing Tools / Difference to make holes in outer polygons
4. merge layer from step 3 with layer from step 2 - Vector / Data management Tools / Merge shapefiles to one

Second option if you have few simple polygons:

1. create outer polygon
2. create hole in polygon (Edit / Add Ring)
3. set snapping (Settings / Snapping Options...)
4. create inner polygon by snapping to inner nodes (hole/ring) of outer polygon

Answer 2

Use the Buffer command, with negative value i.e. -50. Operating in a UTM projection is more intuitive when using this type of action.

Answer 3

I wonder if you might prefer to create your polygons with lines and then polygonise them with the Polygonizer plug-in? See the attached images (and perhaps also have a look at http://confound.me.uk/maps/ppv4.pdf). N.

Answer 4

If I understand you, you have a main polygon which includes many polygons that are close. a) first draw the main polygon

b)Define a ring that surround all inner polygons (I am asuuming this is your case)

c) Make sure you have defined the snapping options as this:

d) Draw the first inner polygon in the ring:

notice since you defined that there must not be intersection of new polygons the inner polygon is correctly created.

e) Define the same way the remaining polygons

If the above description fits your case, that should do it.

Hope it helps

Gerardo