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

[Nicolas Ribot]

Thank you Sandro for this showcase.
I just answer because I do not receive through gmail the answers of
the thread I initiated.
Only answers sent by others, like you Jose. Strange.

Nicolas

On 13 April 2012 15:28, Jose Carlos Martinez <jomarlla at cgf.upv.es> wrote:
> nice example,
> these kind of examples show the power of the  persistent topology.
> thanks to make it.
>
>
> On 13/04/2012 14:42, Sandro Santilli wrote:
>>
>> 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):
>>
>>
>> http://strk.keybit.net/blog/2012/04/13/simplifying-a-map-layer-using-postgis-topology/
>>
>> --strk;
>>
>>   ,------o-.
>>   |   __/  |    Delivering high quality PostGIS 2.0 !
>>   |  / 2.0 |    http://strk.keybit.net - http://vizzuality.com
>>   `-o------'
>>
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