I'm on GRASS 6.4.1. QGIS 1.7.0<br><br><div class="gmail_quote">On Thu, Jun 30, 2011 at 10:18 AM, Markus Metz <span dir="ltr"><<a href="mailto:markus.metz.giswork@googlemail.com">markus.metz.giswork@googlemail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im">On Thu, Jun 30, 2011 at 4:01 PM, Christian Guirreri<br>
<<a href="mailto:christian@guirreri.com">christian@guirreri.com</a>> wrote:<br>
> I'm a brand new user to GIS - my goal right now is to heavily simplify Tiger<br>
> 2010 county and distrct data, without producing gaps between boundaries.<br>
> I've been testing this with v.generalize in grass via QuantumGIS - I've had<br>
> tons of issues with the Grass toolbox crashing, but have narrowed down to<br>
> using the Hermite algorithm. While it works, I'm having some bizarre issues<br>
> with it. Apologies for the cross-post with the PostGIS mailing list.<br>
><br>
> In the attached gif of California counties, from left to right, I have used<br>
> the following tolerance values with the Hermite algorithm:<br>
> - original<br>
> - 1.0<br>
> - 0.08<br>
> - 0.01<br>
> - 0.00001<br>
><br>
> Why do counties disappear entirely as I decrease the tolerance?<br>
><br>
</div>This problem has been fixed in GRASS 6.4 only 2 weeks ago (June 13).<br>
Please update your GRASS version if possible.<br>
<br>
Markus M<br>
<div class="im"><br>
<br>
> In the Grass Tools I choose the v.generalize function. I choose Boundary as<br>
> the feature type (though I've tried checking others, as well as all of them<br>
> and it doesn't seem to change anything). Everything else is default, except<br>
> for tolerance as notated above.<br>
><br>
> When I tested this originally on only Arkansas and Mississippi, I got really<br>
> nice results. I then tried it on the entire US and had the missing counties<br>
> problem. So I tried only California, and still have the same issue.<br>
><br>
> I've tried other algorithms, but this has so far given me the detail I want<br>
> - of course sans counties! Any thoughts?<br>
><br>
> Thanks,<br>
> - Chris<br>
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><br>
</blockquote></div><br>