[postgis-devel] preserve topology while simplifying geometry

Stefan Zweig stefanzweig1881 at web.de
Tue Apr 24 01:05:50 PDT 2007

Hi all,

Maybe this could be a nice feature for a future release of postgis / geos, especially for the simplify(geometry, precision)-function: a simplification algorithm which preserves topology on geometries, especially for the geos spatial analyze functions to prevent the "TopologyException: side location conflict"-error. There is a modificated Douglas-Peucker-Algorithm which prevents a Polyline / Polygon from getting self-intersections by being simplified, in case theese features did not have self-intersections in their original state. So if they had been valid (isvalid()) before simplification they would keep valid afterwards.
unfortunately only little sources to this algorithm can be found on the web. originally it was published in

Saalfeld, Alan. 1999. Topologically Consitent Line Simplification with the Douglas-Peucker-Algorithm. American Congress on Surveying and Mapping. p. 7-18.

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