[postgis-users] Union fails on 2389 linestrings.

[Nicolas Ribot]

> I have a layer with 2389 linestrings which intersect a lot.  I'm
> trying to create a polygon overlay, so I want to union the linestrings
> together so I can then call polygonize.
>
> However, when I try to union them, it runs for about 25 minutes then
> fails claiming it found a non-noded intersection between two lines
> that appear identical and 0-length (though it may be the precision is
> lost when printing the WKT in the error message).
>
>        create table noded_lines as
>        select ST_Union(boundary) as noded_boundary from boundary_lines;
>
> NOTICE:  TopologyException: found non-noded intersection between
> LINESTRING (-118.296 34.1185, -118.296 34.1185) and LINESTRING
> (-118.296 34.1185, -118.296 34.1185) at -118.296 34.1185
>
>
> ERROR:  GEOS union() threw an error!
>
> Anyone know how I could get around this?
>

Hi,
Are all your linestrings valid ?
Could you reduce coordinate precision with st_snapToGrid ?

Nicolas