[GRASS-user] attribute info attached to multiple areas

[Richard Chirgwin]

Sharon M wrote:
> 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.
>   
Sharon,

This seems perfectly valid to me - I don't use WinGRASS so I don't know 
what problems v.digit might have.

As long as the attribute is associated with the correct polygon, all 
should be well.

Richard
> 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
>>
>>     
>
>