[Qgis-developer] some flaw in RDP algorithm?

kimaidou kimaidou at gmail.com
Mon Feb 3 06:29:20 PST 2014


We definitely need a better simplify algo in QGIS than Douglas Peucker. It
is very fast, but does not really preserve the "shape" of polygons/lines
and does not preserve topology. Your work seems interesting. Is you
approach similar to Visvalingam algo (used for example in Mapshaper :
http://mapshaper.org/ ) ? Does it preserve topology ?
Having a simplifier that can preserver topology while being fast like
Visvalingam would be great indeed !

ps: sorry to bring personnal will in response of your topic instead of
really answering your question..


2014-02-03 giulianc51 <giulianc51 at gmail.com>:

> Hi all,
> I do not know if this is the right place to talk about it but I think I
> have found a small problem in the plugin fTools, particularly in the
> "Simplify geometry" of the module "Geometry tool";
> more precisely, the problem is in the RDP algorithm used by the
> function;
> nothing dramatic, the procedure works properly and provides a
> simplified line, but I have isolated some cases in which the solution
> is not optimal: some points, not needed for the definition of the line,
> are left;
> to sum up, I put some considerations in some slides here
> http://www.slideshare.net/giulianc/clean-lines-presentation;
> can you tell me where and how it can be of interest to discuss this
> topic?
> thanks, best regards, sfm+Gtbe(*) :-)
> giuliano curti
> (*) sorry for my (+ Google translation) bad english :-)
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