[GRASS-dev] v.what.rast support for centroids, v.rast.stats speed, r.category update

Michael Barton michael.barton at asu.edu
Wed Oct 10 10:17:13 EDT 2007

I was thinking more along the lines of something where you specified a set
of vector features (cat=... or where=...), clicked run and after a check to
make sure they are closed polylines it would add a central centroid and make
them areas.


On 10/10/07 12:11 AM, "Hamish" <hamish_nospam at yahoo.com> wrote:

> Michael Barton wrote:
>> This brings up an issue that we might want to think about for GRASS 7.
>> Currently, centroids must always be created manually to transform a
>> closed polyline into an area. While we might want to keep this as an
>> option (but maybe not), I think it would be better to have some kind of
>> 'area-creation' utility that would transform a close polyline into an
>> area by automatically adding a centroid at a predefined center location
>> (geometric center or other measure) and adding a cat value. Then
>> analytical utilities like you are discussing here could be more
>> reliable.
> (v.type + v.centroids)
> I don't think you can convert automatically all closed boundaries as
> some of the closed boundaries may be islands/holes within an area, and
> you risk turning them into positives.
> Hamish

Michael Barton, Professor of Anthropology
Director of Graduate Studies
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

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