[GRASS-user] v.generalize issues

[Markus Metz]

On Thu, Jun 30, 2011 at 4:47 PM, Christian Guirreri
<christian at guirreri.com> wrote:
> I'm on GRASS 6.4.1. QGIS 1.7.0
>
In this version, v.generalize is still broken. You would need a recent
version of GRASS 6.4.2. For Windows, you can get a recent version
here:

http://wingrass.fsv.cvut.cz/grass64/

Markus M


> On Thu, Jun 30, 2011 at 10:18 AM, Markus Metz
> <markus.metz.giswork at googlemail.com> wrote:
>>
>> On Thu, Jun 30, 2011 at 4:01 PM, Christian Guirreri
>> <christian at guirreri.com> wrote:
>> > 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?
>> >
>> This problem has been fixed in GRASS 6.4 only 2 weeks ago (June 13).
>> Please update your GRASS version if possible.
>>
>> Markus M
>>
>>
>> > 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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>> > grass-user at lists.osgeo.org
>> > http://lists.osgeo.org/mailman/listinfo/grass-user
>> >
>> >
>
>