[GRASS-user] v.generalize issues

[Christian Guirreri]

Understood. I actually started to try using some of the GRASS interface via
QGIS, but on some of the panels, such as v.generalize, I couldn't type in a
tolerance value. I'm on Win7 x64.

I'm going to try a fresh install of GRASS.



On Thu, Jun 30, 2011 at 10:52 AM, Daniel Lee <lee at isi-solutions.org> wrote:

> I've experienced problems with calling up vectors stored in the GRASS
> database with QGIS, sometimes vectors simply are missing. Does the same
> problem occur in the GRASS environment? Maybe it would help to try showing
> the vectors in GRASS directly. If that work it means that QGIS is just
> having a problem where it calls up the vectors from GRASS. My problem was
> fixable by exporting the vectors as a shapefile and then loading them in
> QGIS.
>
> --
> B.Sc. Daniel Lee
> Geschäftsführung für Forschung und Entwicklung
> ISIS - International Solar Information Solutions
>
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> Am 30.06.2011 16:02 schrieb "Christian Guirreri" <christian at guirreri.com>:
>
> > I'm a brand new user to GIS - my goal right now is to heavily simplify
> Tiger
> > 2010 county and distrct data, without producing gaps between boundaries.
> > I've been testing this with v.generalize in grass via QuantumGIS - I've
> had
> > tons of issues with the Grass toolbox crashing, but have narrowed down to
> > using the Hermite algorithm. While it works, I'm having some bizarre
> issues
> > with it. Apologies for the cross-post with the PostGIS mailing list.
> >
> > In the attached gif of California counties, from left to right, I have
> used
> > the following tolerance values with the Hermite algorithm:
> > - original
> > - 1.0
> > - 0.08
> > - 0.01
> > - 0.00001
> >
> > Why do counties disappear entirely as I decrease the tolerance?
> >
> > In the Grass Tools I choose the v.generalize function. I choose Boundary
> as
> > the feature type (though I've tried checking others, as well as all of
> them
> > and it doesn't seem to change anything). Everything else is default,
> except
> > for tolerance as notated above.
> >
> > When I tested this originally on only Arkansas and Mississippi, I got
> really
> > nice results. I then tried it on the entire US and had the missing
> counties
> > problem. So I tried only California, and still have the same issue.
> >
> > I've tried other algorithms, but this has so far given me the detail I
> want
> > - of course sans counties! Any thoughts?
> >
> > Thanks,
> > - Chris
>
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