[postgis-users] Cut lines with polygon

Tue Oct 6 01:30:33 PDT 2009

Hello postigs uder discussion

i still got the problem with st_intersection. i try this sql

create table osm_polygon_in_grossring25_50 as 
SELECT b.way_id, b.geom,  
st_Intersection ( g.geom, b.geom )
 FROM stadtgrossbuffer25_50 AS g, osm_valid_polygon AS b
 WHERE IsEmpty ( st_Intersection ( g.geom, b.geom ) ) = FALSE;

but the lines or polygons won´t get cut out. all lines and polygones that are in contact with the buffer get selected and not cut at the border of the buffer. i checked the output with sql und via desktop gis. in the attatchment are two jpg with the output?

has anyone a idea?

alex

-------- Original-Nachricht --------
> Datum: Mon, 5 Oct 2009 15:37:43 +0200
> Von: Brian Modra <brian at zwartberg.com>
> An: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
> Betreff: Re: [postgis-users] Cut lines with polygon

> 2009/10/5 Alexander Strunck <A.Strunck at gmx.net>:
> > Hello
> >
> > i checked if its a rendering problem. but that´s not it. for example i
> have a polygon with a hole in it and one line yust go through this hole...
> 
> take a look at this:
> http://postgis.refractions.net/documentation/manual-svn/ch04.html#OGC_Validity
> 
> > how can i find the poylgon that throughs this error? i have no idea...
> 
> I assume they all have UIDs?
> Do it iteratively:
> start with one half of the table (limited by UID range)
> If that throws the error, then try one half of that half, etc... unil
> you are down to one polygon.
> 
> >
> >
> > alex
> >
> >
> >
> > -------- Original-Nachricht --------
> >> Datum: Mon, 5 Oct 2009 14:57:44 +0200
> >> Von: Brian Modra <brian at zwartberg.com>
> >> An: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
> >> Betreff: Re: [postgis-users] Cut lines with polygon
> >
> >> 2009/10/5 Alexander Strunck <A.Strunck at gmx.net>:
> >> > Hello
> >> >
> >> > i am really new to postgis and i try to cut lines with a polygon. the
> >> sql statement is
> >> >
> >> > create table osm_line_in_dorfring2_5_10 as
> >> > SELECT b.way_id, b.geom,
> >> > Intersection ( g.geom, b.geom )
> >> >  FROM stadtdorfbuffer2_5_10 AS g, osm_line AS b
> >> >  WHERE IsEmpty ( Intersection ( g.geom, b.geom ) ) = FALSE;
> >> >
> >> > but when i look at the result the lines are not cut by the polygon.
> the
> >> lines go a little bit over the borders of the polygon. Why is that?
> >>
> >> Have you checked the coords and done the maths (manually) to see if
> >> the intersection points are wrong? Maybe its just a rendering problem
> >> in whatever you are using to view them?
> >>
> >> > the second problem ist when i want to do the same thing with two
> >> different polygon tables. i get the error
> >> > NOTICE:  TopologyException: found non-noded intersection between
> >> 8.18405 48.9483, 8.18366 48.9481 and 8.18285 48.947, 8.18933 48.9551
> 8.18381
> >> 48.9482
> >> > ERROR:  GEOS Intersection() threw an error!
> >> >
> >> > ********** Fehler **********
> >> >
> >> > ERROR: GEOS Intersection() threw an error!
> >> > SQL Status:XX000
> >>
> >> See if you can find the polygon that its throwing this for, and view
> >> it to see if there is something obvious about the topology.
> >>
> >> >
> >> > i tested the polygon tables with ST_IsValid and everything seems to
> be
> >> all right.
> >> >
> >> > does someone have any suggestions?
> >> >
> >> > thx in advance
> >> >
> >> > alex
> >> > --
> >> > GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
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> >> >
> >>
> >>
> >>
> >> --
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> >> Mobile: +27 79 69 77 082
> >> 5 Jan Louw Str, Prince Albert, 6930
> >> Postal: P.O. Box 2, Prince Albert 6930
> >> South Africa
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> 
> 
> -- 
> Brian Modra   Land line: +27 23 5411 462
> Mobile: +27 79 69 77 082
> 5 Jan Louw Str, Prince Albert, 6930
> Postal: P.O. Box 2, Prince Albert 6930
> South Africa
> http://www.zwartberg.com/
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users

-- 
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Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01
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