[postgis-users] Break lines at intersections

[Horst Düster]

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Hi

if you work with PostGIS < 2.0 you can use the cleangeometry() function.

http://www.kappasys.ch/pgtools/cleangeometry/cleanGeometry.sql

Regards
Horst

Dr. Horst Düster
Kappasys
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CH-4500 Solothurn

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Am 28.03.2012 12:29, schrieb Pavel Iacovlev:
> Hello,
> 
> Anyone has any ideas/tips of how to break lines at intersections ?
> I have a a layer of lines and I want to break them at intersections
> with them selfs, also (not that important but would be nice) break
> lines forming a collapsed loop, for example 0.0;1.0;0.0 is broken at
> 1.0.
> 
> Currently this can be done in grass with v.clean tool=break,rmdupl but
> it's relatively hard to add GRASS to a web app.
> 
> So far I came up with this query and out of ideas right now:
> 
> SELECT DISTINCT
> gid,
> ST_AsText(intersect_geom),
> ST_Line_Locate_Point(GeometryN(the_geom, 1), intersect_geom) as point_loc1
> FROM
> 
> (SELECT a.gid, ST_Intersection(a.the_geom, b.the_geom) AS
> intersect_geom, a.the_geom
> FROM roads as a, roads as b
> WHERE ST_Intersects(a.the_geom, b.the_geom) AND (a.gid = 1)
> ) AS res1
> 
> WHERE GeometryType(intersect_geom) = 'POINT' -- Need support for
> MULTILINESTRINGS, take start and end point ?
> ORDER BY point_loc1
> 
> which has the following result: http://jsfiddle.net/9RJ8a/
> I have the line, and the point positions on the line, but I can't get
> around how to create my NEW broken lines with
> ST_Line_Substring(geometry a_linestring, float startfraction, float
> endfraction)
> 
> Any suggestion of how to accomplished this ? is the approach correct ?
> any other ideas ?
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
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