[postgis-users] Break lines at intersections

Nicolas Ribot nicolas.ribot at gmail.com
Wed Mar 28 08:04:29 PDT 2012

On 28 March 2012 15:43, Pavel Iacovlev <iacovlev.pavel at gmail.com> wrote:
> Thank you for you help Sandro,
> As I understand something like this in theory:
> SELECT ST_Node(ST_Collect(the_geom)) FROM roads;
> Then I generate series from the result and using ST_Contains find to
> what initial "road" geometry the segment belongs and get it's gid or
> another attribute.
> Also you know (or maybe someone else knows) is it possible to
> accomplish this in PostGIS 1.5 ?

Yes it is. Look at st_union() and st_dump.
st_union will cut the lines at their intersection points:

select st_astext((st_dump(st_union(geometry))).geom) from lines;

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