[Qgis-developer] some flaw in RDP algorithm?

[Jonathan Moules]

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

http://grass.osgeo.org/grass64/manuals/v.generalize.html

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.

Cheers,
Jonathan



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 :-)
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>
>
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