[GRASS-user] generalize polygons including holes

[Robert Nuske]

Hi Markus

> >>>> v.generalize does not distinguish between outer and inner rings, it
> >>>> simply goes through all boundaries and generalizes each one.
> >>> 
> >>> And this has always been the case or this is specific to GRASS7 ?
> >> 
> >> This has always been the case.
> > 
> > Then why doesn't there seem to be any generalization happening for the
> > hole
> > boundaries of the test dataset with grass64release ?
> 
> With the test dataset you provided, GRASS 6.4 does generalize the hole
> boundaries. I do not have the problem vector of Robert, so I can not
> say if the hole boundaries in that vector are generalized or not.

Please find attached a location with a test dataset (snipped of larger vector 
map) and two images from generalizations carried out in GRASS 6.4.4 
(6.4.4-1~trusty5 from ppa:ubuntugis-unstable) and GRASS 7.0 
(7.0.0+1svn64474~ubuntu14.04.1 from ppa:grass-devel). 
Blue layer is generalized and red one is the original both at 50% 
transparency.


For me, the results from GRASS 7.0 look as expected (inner rings generalized) 
but v.generalize in GRASS 6.4 seems not to treat inner rings.



GRASS 6.4.4
-----------------------------------------------------------
v.generalize in=test_data out=test_gen method=douglas thresh=5000

Number of vertices for selected lines reduced from 907 to 82 (9%).
v.generalize complete.


GRASS 7.0
-----------------------------------------------------------
v.build map=test_data
v.generalize in=test_data out=test_gen method=douglas thresh=5000

v.generalize complete. Number of vertices for selected features reduced
from 4605 to 451 (9%).



cheers,
  robert
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