[GRASS-user] v.generalize issues

[Daniel Lee]

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

Deutschhausstr. 10
35037 Marburg
Festnetz: +49 6421 379 6256
Mobil: +49 176 6127 7269
E-Mail: Lee at isi-solutions.org
Web: http://www.isi-solutions.org
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20110630/cbd94cac/attachment.html