[GRASS-dev] v.category report area

[Benjamin Ducke]

Hi,

On 04/12/2013 03:05 PM, Martin Landa wrote:
> Hi all,
>
> `v.category` (G7) reports categories also for areas.
>
> v.category rb opt=report
> Layer: 1
> type       count        min        max
> point          0          0          0
> line           0          0          0
> boundary       0          0          0
> centroid       1          1          1
> area           1          1          1
> face           0          0          0
> kernel         0          0          0
> all            1          1          1
>
> Categories are assigned only to the centroids. Areas (topological
> composition of boundaries and centroid) shouldn't  be reported by
> `v.category`, I would say (?)
>
> Martin
>

<it seems to me that there hasn't been any reply
to this by someone more qualified then myself(?)>

My understanding is the same as Martin's:
in the case of areas, categories are attached to
centroids, so the above output is a bit confusing.

However, since "areas" do not physically exist in
a GRASS map (only the centroids and boundaries do),
there is a problem here: what if some centroids are
without a category, but still part of an area?
What if there are centroids with categories that are
not placed correctly within a boundary? This
could happen in incomplete or incorrect maps.
And in these cases the difference between the
stats for "centroid" and "areas" can be important
information.

Perhaps instead of always outputting the "area" line,
the module should only output an extra line (or even
a warning) if there is a mismatch between the number
of categorized areas and centroids.

Best,

Ben

> --
> Martin Landa <landa.martin gmail.com> * http://geo.fsv.cvut.cz/~landa
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-- 
Dr. Benjamin Ducke, M.A.
{*} Geospatial Consultant
{*} GIS Developer

   benducke at fastmail.fm