[Qgis-user] how to simplify polygons without loosing too much information

[Benjamin Ducke]

Note that there is also "v.generalize" (if you have the GRASS provider
activated in Processing). It implements many additional algorithms and
provides a comprehensive Help page.

It would be interesting to know which algorithm (and parameters) gave
you the best results!

Best,

Ben


On 27/06/2022 16:58, Johannes Kröger (WhereGroup) via Qgis-user wrote:
> Hey Michael,
> 
> the algorithms involved are Douglas-Peucker and Visvalingam. With those 
> terms you might find some nice explanations and guidance online. Some 
> quick links:
> 
> - http://bl.ocks.org/msbarry/9152218
> - https://dulldrums.github.io/polygon-reduction-algorithms-demo/
> - https://ignf.github.io/CartAGen/docs/algorithms/line/visvalingam.html
> 
> For your use case (keeping the overall shape) I would try Visvalingam 
> first as that is pretty much its goal too.
> 
> Cheers, Hannes
> 
> 
> Am 27.06.22 um 16:52 schrieb Michael.Dodd via Qgis-user:
>>
>> I know there are various simplify tools in qgis but perhaps I don’t 
>> understand how to use them best. I want to simplify i.e. reduce the 
>> number of nodes in a polygon without changing the overall shape too 
>> much for country or similar outlines.  When I have tried this the 
>> simplify tends to chop off bits that a human doing a manual 
>> simplification would not, in some areas the simplification could loose 
>> loads of nodes whereas in other areas it needs to keep more of them or 
>> the overall shape will be greatly changed. Is there anyway round this 
>> or am I asking for something that is not logical?
>>
>>
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> 
> -- 
> Johannes Kröger / GIS-Entwickler/-Berater
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