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List:       postgis-users
Subject:    Re: [postgis-users] Overlapping of polygons with SimplifyPreserveTopology
From:       Luca Morandini <lmorandini () ieee ! org>
Date:       2013-12-12 20:50:07
Message-ID: l8d7hl$q59$1 () ger ! gmane ! org
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On 11/12/13 19:15, Sandro Santilli wrote:
>
> A topological approach would solve it.
> Simplifying a polygon may overlap with the still-unsimplified
> adjacent one, so you can't check after each single simplification.
> You could check afterwards, at the end, but then resolving one
> overlap on one side may introduce another overlap in the other side.
>
> Really, you need to model your data topologically, then simplify
> edges, rather than full polygon boundaries.

Actually, I simplified (with ST_SimplifyPreserveTopology) one edge at a time, but 
did not check at every step (I was under the impression that this function did 
preserve topology).


> See http://strk.keybit.net/blog/2012/04/13/simplifying-a-map-layer-using-postgis-topology/

Thanks, this did the trick. It would be useful to add it to PostGIS.

Regards,

Luca Morandini
Data Architect - AURIN project
Melbourne eResearch Group
Department of Computing and Information Systems
University of Melbourne
Tel. +61 03 903 58 380
Skype: lmorandini

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