[postgis-users] ST_snap doesn't snap within the tolerance

[Sandro Santilli]

Snapping has a few limitations.
One is that only vertices in the target are considered as snap points,
so you'll never get a vertex of first geometry snapped against a segment
of the second.

See if this could explain your problem. 

--strk;

On Wed, Jul 11, 2012 at 12:50:30PM +0000, Astrid Bjørnerød wrote:
> I want some polygons (with attribute artype=21) to snap into some neighbor-polygon. I have set the tolerance to 5m.
> Put not all of the polygons in the result has been snapping, the gap is under the tolerance.
> The sql:
> create table test_ar5jm.snipsnap AS SELECT p1.jmsign,ST_Union(ST_Buffer(ST_Snap(p1.geo,p2.geo, 5),0)) as geo
> FROM test_ar5jm.temp_aij_flate
> AS p1 CROSS JOIN test_ar5jm.temp_aij_flate As p2
> WHERE p1.artype = 21
> GROUP BY p1.jmsign;
> 
> Figures from QGis before snapping and after snapping in attachedment.
> 
> Vennlig hilsen
> Astrid Bjørnerød
> 
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