[postgis-users] Simplifying a multipolygon layer, keeping polygon connection

Sandro Santilli strk at keybit.net
Fri Apr 13 05:42:26 PDT 2012

On Wed, Apr 11, 2012 at 02:59:41PM +0200, Sandro Santilli wrote:

> Alternatively you could still construct the topology with full-precision
> edges and then simplify the edges in-place (possibly after a CopyTopology),
> using ST_ChangeEdgeGeom. That way the _original_ nodes will remain the same
> and you'd be only simplifying the edges connecting them. Beware in this
> case that simplification might still introduce topology errors but such
> errors would be cought by ST_ChangeEdgeGeom with throwing an exception.
> You may catch the exception to reduce tolerance for a given edge or bypass
> all checks by editing the edge_data table directly and cross your fingers :)
> ValidateTopology should then tell you what you broke, if you want to fix
> manually after the fact.

FYI, I wrote a blog post showcasing this approach (with code):



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