[postgis-users] Cut lines with polygon

[Alexander Strunck]

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?

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

i tested the polygon tables with ST_IsValid and everything seems to be all right.

does someone have any suggestions?

thx in advance

alex
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