[Community] Shapely and polygon simplifications

[Sean Gillies]

Agreed. A default tolerance must not be tolerated ;)

On Nov 10, 2009, at 7:02 PM, Helge Jensen wrote:

> With regards to the choice between mirroring the GEOS api or a more  
> "pythonic" approach, please take my input with a grain of salt as I  
> have only just started using shapely :)
>
> However you already have pythonic wrapping of the geometries and  
> have simplify(*) as member-functions, not free functions, so my  
> personal feeling about it is that you are already quite a long way  
> down the road of a pythonic library and not a mirror of the geos API.
>
> Shapely doesn't "feel" like GEOS, nor is it limited to GEOS, and  
> frankly, it is nice with a pythonic python-gis library for a change  
> (as opposed to, the GDAL bindings for example).
>
> I don't think there are any strong candidates for a default tolerance.
>
> One could argue (very weakly, in my eyes) for either 0.0, float- 
> epsilon or 1.0 as the default tolerance, but I think those are all  
> rather sought. I would personally prefer that there was no default.
>
> On Tue, Nov 10, 2009 at 1:36 PM, Aron Bierbaum  
> <aronbierbaum at gmail.com> wrote:
> I had considered adding something like that, but I didn't know if
> Shapley was meant to mirror the GEOS API more closely. I completely
> agree that it makes more sense as a single method. It appears that
> people agree that by default we should preserve topology too.
>
> I also tried to find a default value for the tolerance. Any ideas
> opinions on a default for this? As far as I could tell there was no
> default in GEOS?
>
> -Aron
>
> Aron Bierbaum
> Software Engineer
> Priority 5
>
> On Nov 10, 2009, at 4:40 AM, Helge Jensen <hej at actua.dk> wrote:
>
> > By the principle of "least-surprise" preserve_topology should
> > probably default to True.
> >
> > Powerusers will probably know that preserve_topology=True is more
> > costly. Perhaps documentation could reflect this?
> >
> > There is some documentation in the GEOS headers
> > (DouglasPeuckerSimplifier.h and TopologyPreservingSimplifier.h) that
> > could be repeated for the simplify function.
> >
> >
> > --
> > Helge Jensen
> > Partner & Senior Software Developer
> >
> >
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>
> -- 
> Helge Jensen
> Partner & Senior Software Developer
>
>
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--
Sean Gillies
Programmer
Institute for the Study of the Ancient World
New York University



--
Sean