[postgis-users] clip polygons

[Marta Debolini]

Thank you all!
I followed your instructions and fixed the problem.

Marta

On Tue, Jan 15, 2013 at 8:16 AM, Francois Hugues
<hugues.francois at irstea.fr>wrote:

> Hello,
>
> To complete these answers about the usage st_intersection in combination
> with st_intersects, if  you want to avoid to clip features "which simply
> intersect the border" you should try to add st_touches(a.geom, b.geom) =
> 'f' in the where clause.
>
> Hugues
>
>
>
> --
>
>
>
> Hugues FRANÇOIS
>
> IR - UR DTM
>
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>
> Cemagref - IRSTEA Grenoble
>
> 2, rue de la papeterie
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>
>
> ________________________________
>
> From: postgis-users-bounces at lists.osgeo.org [mailto:
> postgis-users-bounces at lists.osgeo.org] On Behalf Of Martin Davis
> Sent: Tuesday, January 15, 2013 5:42 AM
> To: postgis-users at lists.osgeo.org
> Subject: Re: [postgis-users] clip polygons
>
>
> Correct.  See http://postgis.net/docs/manual-2.0/ST_Intersection.html
>
>
> On 1/14/2013 5:14 PM, Tim-Hinnerk Heuer wrote:
>
>
>         I think Nicolas is more correct. St_Intersection sounds like a
> function that gets a geometry while St_Intersects returns a Boolean.
>
>         On Jan 15, 2013 6:24 AM, "Francisco Salas" <
> fsalas at pinar.geocuba.cu> wrote:
>
>
>                 Martha ,
>
>                 I think that you must use in the select sentence
> st_intersects(a.the_geom, b.the_geom) as the_geom , instead of a.the_geom
>
>
>
>                 Francisco Salas
>
>
>
>
>
>                 De: postgis-users-bounces at lists.osgeo.org [mailto:
> postgis-users-bounces at lists.osgeo.org] En nombre de Marta Debolini
>                 Enviado el: lunes, 14 de enero de 2013 12:01 p.m.
>                 Para: postgis-users at lists.osgeo.org
>                 Asunto: [postgis-users] clip polygons
>
>
>
>                 Hi,
>                 I am a new postgis user, so sorry if my request seems
> trivial for someone.
>
>                 I have to clip a polygon with another polygon file. I was
> used to do this operation with the simple comand "clip" in GRASS or QGIS.
>                 How can I do the same operation in postgis? I tried with
> sy_intersect, but it takes also the polygons outside my area, which simply
> intersect the border.
>                 The request I wrote is:
>
>
>                 CREATE TABLE w_md.x
>                 AS (SELECT area, a.the_geom
>                     FROM oc a, co b
>                     WHERE st_intersects(a.the_geom, b.the_geom));
>
>                     ALTER TABLE w_md.x_1999 ADD column ggid1 serial;
>                      ALTER TABLE w_mdi.x_1999 ADD PRIMARY KEY (ggID1);
>
>                 Thank you for your help,
>
>                 Marta
>
>
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