[Qgis-user] RE: polygon overlay

[Giovanni Manghi]

Hi,


> Hi everyone, I could be wrong, but I thought they were asking 
> how to use an object to clip another object in the same layer.

yes, as it resulted by an off list exchange with the original poster.


> Ftools can only use all the objects in a layer to clip all 
> the objects in a different layer, producing a new layer.  
> This can obviously still be used to achieve the desired 
> outcome, but it will require the use of several 
> temporary files and copying and pasting objects between files.


right.



> It would be very nice if features like clipping were 
> implemented kind of as advanced digitising features, 
> so they could operate with/on selected features. 
> But I imagine this would need a reasonable amount of work from someone.


the original problem was: "I have a polygon vector and sometimes I add
to it new polygons, but not digitizing them, for example downloading
tracks from a GPS. The new polygon obviously will not be perfectly
adjacent to the existing one and I need a tool that clips (and fill)
where needed (the new polygon)."

Using the "avoid intersection of new polygons" and the "reshape tool" it
can be done, but it is bit tricky, especially if the "common" border has
a lot of nodes.

I agree that a ad hoc tool would be better.

Cheers

-- Giovanni --