[GRASS-dev] Areas

[Michael Barton]

At the risk of sounding naïve, don't boundaries without centroids behave
pretty much as lines? In this case the cat is attached to the boundary/line.
However, a boundary/centroid pair becomes an area. Then the cat is attached
to the centroid/point instead of the boundary/line.

It seems a good idea to somehow enforce this kind of organization as much as
possible to avoid the possibility of some weird hybrid of boundary with
attributes and centroids with attributes for the same area object. Althought
I'm sure someone can think of a real-world situation where this might be
useful, IMHO, it seems a better idea analytically and conceptually to keep
these separate. This leave us functionally with points, lines/arcs, and
areas/polygons. Boundaries are either lines (without centroids) or areas
(with centroids).

Michael
__________________________________________
Michael Barton, Professor of Anthropology
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



> From: Maciek Sieczka <werchowyna at epf.pl>
> Date: Mon, 29 May 2006 21:46:47 +0200
> To: Wolf Bergenheim <wolf+grass at bergenheim.net>
> Cc: <grass-dev at grass.itc.it>
> Subject: Re: [GRASS-dev] Areas
> 
> On Mon, 29 May 2006 13:40:55 +0300 (EEST)
> Wolf Bergenheim <wolf+grass at bergenheim.net> wrote:
> 
>> Hi!
>> 
>> When starting to think about areas I played with v.digit a bit, and
>> it seems that it creates different cat for the boundary and centroid.
> 
> Only if you request it. You can digitize a boundary (any other feature
> too) without category. Or with any cat you specify manually, eg. if you
> want to attach the new feature to an existant datatable entry.
> 
>> Is this what we want? I've always thought of them as kind of bound
>> together, and thus would expect them to have the same cat.
> 
>> Am Itotally off base here? What about islands? Should they have a cat
>> at all, or should they have the same cat as the area that they belong
>> to? Or something totally different?
> 
> When digitising adjacent areas (sharing a common border line),
> categories for boundaries are redundant, if not a disturbance. We
> only need cats for centroids then. This also solves the problem of
> islands. When the island boundary doesn't have a cat attached,
> attributes belong only to centroids in the surroning areas - and no
> problem.
> 
> That's at least the way I see it.
> 
> Maciek
> 
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