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How to avoid deleting small polygons when using Generalizer ?

  • April 16, 2014
  • 5 replies
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I have a dataset containing large and small polygons. When I generalized the layer, preserving the shared boudnaries, small pieces get deleted.

 

 

Is there w way to avoid deleting small polygons ?

Best answer by gio

Apart form filtering small sized polygons.

 

The various generalising schemes have options to control the amount of generalizing.

 

If u have it generalise to much, small objects will enter the range of generalisation and be removed altogether.

 

 

So its about tolerances, smoothingfactors, angels etc.. Experiment with these will help.

 

 

Gio

 

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5 replies

david_r
Celebrity
  • April 16, 2014
Hi,

 

 

that would probably depend on the algorithm selected in the Generalizer.

 

 

Which algorithms have you tried?

 

 

David

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  • Author
  • April 16, 2014
I use Douglas

 

 

Thanks

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  • Author
  • April 16, 2014
The best result is when I use Douglas. Other algorithm still removed objects.

 

 

However, I have a work around using "Changedetector" then "Clipper" that will reinsert the removed objects.

 

 

Generalizer should maybe have an option "prevent shape removal" , as seen on mapshaper (http://www.mapshaper.org)

gio
Contributor
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  • Contributor
  • Best Answer
  • April 16, 2014
Apart form filtering small sized polygons.

 

The various generalising schemes have options to control the amount of generalizing.

 

If u have it generalise to much, small objects will enter the range of generalisation and be removed altogether.

 

 

So its about tolerances, smoothingfactors, angels etc.. Experiment with these will help.

 

 

Gio

 


gio
Contributor
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  • Contributor
  • April 16, 2014
well..not with angels of course..angles are more usefull here...:)