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List: postgis-users
Subject: Re: [postgis-users] Recommendations with GRASS v.generalize() on
From: Dan Putler <dan.putler () sauder ! ubc ! ca>
Date: 2011-06-30 3:08:13
Message-ID: 4E0BE89D.7020702 () sauder ! ubc ! ca
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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
> <christian@guirreri.com <mailto:christian@guirreri.com>> 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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