[Qgis-developer] some flaw in RDP algorithm?

Jonathan Moules jonathanmoules at warwickshire.gov.uk
Wed Feb 5 03:31:25 PST 2014

QGIS already has access to tons of generalisation options via the grass
v.generalise tool


Split into four categeories - Generalisation, Smoothing, Displacement,
Network Generalisation.

Is there a reason those can't be used? I wonder how many implementations of
Douglas Peucker QGIS already has? Re-implementing other ones when they
already exist doesn't seem optimal. Of course maybe you want a new one, but
then I'd suggest maybe it could be added to Grass and that in turn would
automatically feed into QGIS.


On 3 February 2014 14:29, kimaidou <kimaidou at gmail.com> wrote:

> Hi,
> 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..
> Michael
> 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 :-)
>> _______________________________________________
>> Qgis-developer mailing list
>> Qgis-developer at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
> _______________________________________________
> Qgis-developer mailing list
> Qgis-developer at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-developer

This transmission is intended for the named addressee(s) only and may 
contain sensitive or protectively marked material up to RESTRICTED and 
should be handled accordingly. Unless you are the named addressee (or 
authorised to receive it for the addressee) you may not copy or use it, or 
disclose it to anyone else. If you have received this transmission in error 
please notify the sender immediately. All email traffic sent to or from us, 
including without limitation all GCSX traffic, may be subject to recording 
and/or monitoring in accordance with relevant legislation.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20140205/5cf12bcb/attachment-0001.html>

More information about the Qgis-developer mailing list