[GRASS-user] attribute info attached to multiple areas

[Sharon M]

Hello Richard,

Thanks for your ideas, and apologies for delay in responding.

I'm new to winGRASS and GIS, so not quite sure how to use v.digit (and
the man page is a bit thin).

You are right in describing the area like a doughnut. In my case, both
the outside and inside areas have centroids created automatically
during the import of the mid/mif files. It's just that the inside area
is linked to both the outside data and it's own data.

Using the doughnut as the example, if the outside area is cat=95 and
the inside area has cat=95/94 (with 94 being the correct cat value),
I've tried:
1) extract the "correct" overlapping area from the source vector map
using v.extract cat=94 to a new map
2) delete the "correct" area from the source vector map using v.edit
tool=delete cats=94
3) extract all areas from the source map except the "correct" area and
save to new map using v.extract -r cat=94
4) patch the 2 new maps together using v.patch -e (copy the attribute
table as well) and save map
5) clean the map using v.clean tools=break,snap,rmdupl,rmdac,rmsa

result is it seems to work, I'm just unsure if this is a valid method.

Does anyone have any thoughts? ideas? on this.

Thanks,

Sharon

>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Thu, 20 Aug 2009 09:44:34 +0930
>> From: Sharon M <morrisxs09 at gmail.com>
>> Subject: [GRASS-user] attribute info attached to multiple areas
>> To: grass-user at lists.osgeo.org
>> Message-ID:
>>        <7a0cde410908191714ja3439dbw36f1c112428157ca at mail.gmail.com>
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> Hi,
>>
>> I'm using WinGRASS-6.4.0SVN-r38537-1 (on Windows XP) and imported a
>> .MIF/.MID files via v.in.ogr using default settings. I get the
>> following message
>>
>> "6 areas represent more (overlapping) features, because polygons
>> overlap in input layer(s). Such areas are linked to more than 1 row in
>> the attribute table. The number of features for those areas is stored
>> as category in layer 2."
>>
>> I've identified one of these (overlapping) areas and found the vector
>> data contains an area completely surrounding another area. The problem
>> is the outside area's attribute information is also being attached to
>> the inside area - how can this association be removed as the inside
>> area has it's own attribute information?
>>
>> Any help would be appreciated.
>>
>> Thanks,
>>
>> Sharon
>>
>
> Sharon,
>
> Since you don't have that many areas to deal with, you could do it manually.
> What you want to do is get the outside area without the inside area - the
> doughnut without the hole!
>
> For example, in v.digit you could attach a centroid to the outside area, and
> then fill in its information from the database.
>
> Richard Chirgwin
>