[Qgis-user] Overlay request

[Jacolin Yves]

Le Tuesday 08 September 2009 11:43:19 Alex Mandel, vous avez écrit :
> Jacolin Yves wrote:
> > Le Tuesday 08 September 2009 10:58:57 Jacolin Yves, vous avez écrit :
> >> Hello,
> >>
> >> Is it possible to do an overlay request on two layers in QGIS?
> >>
> >> I would like to get a new layer showing features of layer A overlaying
> >> features of layer B.
> >>
> >> thanks,
> >>
> >> Y.
> >
> > One information: my layers are not in a postgis layer and I would like to
> > avoid to import them (yes I am lazy :p )
> >
> > Does fTools will add such feature?
> >
> > Y.
>
> Yes Clip should do what you want, it can also be achieved via an
> intersect, although that will merge the attribute tables in the overlap
> and possibly cut polygons.
>
> I wrote a modification to the old geoprocessing tool called an extract
> which is very similar but is a select by overlap instead of a cut. It's
> very similar to v.extract in grass. I can post if that's what you need
> and maybe we can get Carson to add it to ftools.
>
> Alex
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Hello,

Thans Alex but I don't think it is what I want.

Actualy I would like to do select feature overlapping another layer. See 
picture : http://img171.imageshack.us/i/qgisclip.jpg/

I want to get feature inside blue polygon, see the one at the top left with 
some part outside the picture :/

This is not a geotreatment, just a spatial select.

In postigs I can do it with something like :
SELECT f.* FROM layer1 AS f, layer2 AS l WHERE 
ST_Overlaps(f.the_geom,l.the_geom)=true

I tried to use "spatial select" in fTools (search tools>spatial select I am 
not sure of the title in english as my GUI is in french) but it fails with an 
error message.

Regards,

Y.
-- 
Yves Jacolin

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