[postgis-users] topology example

[Sandro Santilli]

On Thu, Feb 23, 2012 at 11:31:13AM +0100, Denis Rouzaud wrote:
> Hi Sandro,
> 
> Thanks a lot!
> Can you also give me hint on what to do when I have an error:
> psql:topology.sql:14: ERROR:  SQL/MM Spatial exception - point not on edge

Upgrade to latest GEOS and PostGIS
(don't forget to load the topology_upgrade.sql file!)

If the problem persists split your update calls in smaller
ranges until you hit the exception. Further reduce the chunk
until you get (if ever) to the offending geometry.

Note that order in which geometries are added into the topology
matters so you may even NOT seeing the problem anymore when changing
such order.

> Basically, I wanted to create the topology to check it...
> I think I cannot do anything with validatetopology until toTopoGeom
> is achieved right?

Well, ValidateTopology only checks the primitives, not the higher
level features. If you know GRASS higher level features validation
is the presence polygon-0 and polygon-2 objects.

If all you want is primitives validation you could use ST_CreateTopoGeo
passing it a collection of all your pipes.

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