Hi Chris,
Your question on QGIS and GRASS was posted to the PostGIS user list.
While you might get a response, this seems like a question for the QGIS
user list since it actually doesn't involve PostGIS.
Dan
On 06/29/2011 03:55 PM, Christian Guirreri wrote:
Narrowed down some test to using the "Hermite" algorithm, but I'm
having some bizarre issues with it.
In the attached gif of California counties from Tiger data, from left
to right, I have the following tolerance values:
- original
- 1.0
- 0.08
- 0.01
- 0.00001
Why do counties disappear entirely as I decrease the tolerance?
Setup is QuantumGIS with GRASS. In the Grass Tools I choose the
v.generalize function. I choose Boundary as the feature type (though
I've tried checking others and it doesn't seem to change anything).
Everything else is default, except for tolerance as notated above.
When I tested this original 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 what I want.
Any thoughts?
- Chris
On Wed, Jun 29, 2011 at 5:10 PM, Christian Guirreri
<[email protected] <mailto:[email protected]>> wrote:
I'm currently going through the GRASS v.generalize() function's
various parameters in QuantumGIS. There's so many options, I'm not
entirely sure what's best. Has anyone tried this on Tiger 2010
counties or district data? Any particular recommendations?
What's most important to me, as mentioned in a previous thread, is
that there are no gaps between counties/districts in a similar
fashion to MapShaper.
Thanks,
- Chris
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