[GRASS-user] v.generalize threshold and boyle's algorithm

[Johannes Radinger]

Hi Markus,

-------- Original-Nachricht --------
> Datum: Tue, 7 Feb 2012 18:00:26 +0100
> Von: Markus Metz <markus.metz.giswork at googlemail.com>
> An: Johannes Radinger <JRadinger at gmx.at>
> CC: grASS user list <grass-user at lists.osgeo.org>
> Betreff: Re: [GRASS-user] v.generalize threshold and boyle\'s algorithm

> Johannes Radinger wrote:
> > Hello,
> >
> > after some month a tried an script again which
> > calls v.generalize. It seems that this module
> > has changed in version 6.4.2 and 6.5SVN.
> >
> > Before I could use following:
> > grass.run_command("v.generalize",
> >                      input = input,
> >                      output = "vector_gen",
> >                      method = "boyle",
> >                      look_ahead = 8,
> >                      overwrite = True)
> >
> > Now it seems that v.generalize needs a threshold value (required!)
> > although the manual states only: Input parameters: input, look_ahead
> 
> Right, the module requires threshold, but Boyle (and some other
> methods) do not require threshold, instead they require other
> parameters. Threshold being required is maybe annoying, but not that
> serious, more serious is that the module does not check if all
> parameters for the selected method are specified.
> >
> > I am confused now if this value is really necessary for calculating
> boyle's algorithm and if yes how should a value be choosen?
> 
> Threshold is not used by boyle, just give the module some dummy value.

Thank you for that answer. Of course its not of big deal to provide a dummy value, I was just confused. 

/johannes

> >
> > Moreover I'd like to know what means the 'r' flag (backwards
> compatibility), were there any major changes in recent time (last year)?
> 
> A number of bugs were fixed because v.generalize produced corrupt
> output in 6.4.1 (see e.g. recent ml thread [1]).
> 
> Markus M
> 
> [1] http://lists.osgeo.org/pipermail/grass-user/2012-January/063327.html

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