[GRASS-user] Unable to get rid of duplicate polygons

[David J. Bakeman]

David J. Bakeman wrote:
> Markus Neteler wrote:
>> On Sun, Apr 1, 2012 at 9:45 PM, David J. 
>> Bakeman<dbakeman at comcast.net>  wrote:
>>> I didn't find an answer in the archives so.
>>>
>>> I have a shapefile of polygons and some of the polygons are 
>>> duplicated.  I
>>> thought I could use v.clean tool=rmdupl to get rid of these 
>>> polygons.  I use
>>> v.in.ogr to read it in and I get the following:
>>>
>>> WARNING: 8 areas represent more (overlapping) features, because 
>>> polygons
>>>           overlap in input layer(s). Such areas are linked to more 
>>> than 1
>>>           row in attribute table. The number of features for those 
>>> areas is
>>>           stored as category in layer 2
>>>
>>> That is correct in that there are 8 duplicate polygons but the only
>>> different attribute is the cat which grass added?  What am I 
>>> missing?  I
>>> then tried v.clean tool=bpol,rmdupl and nothing changes it still has 
>>> the 8
>>> duplicates.  What am I doing wrong?
>> I think that you need to add the break tool for v.clean.
> Correct that was actually what I was using:  v.clean tool=break,rmdupl
>
> Looking closer I see that when I run v.clean it doesn't even report 
> the duplicates that v.in.ogr did but they are still there.  The only 
> thing that differs in coordinates or attributes is the cat attribute 
> that grass added.
>>> I am using grass 6.3.0 on fedora core 14 linux.
>> Please note that you can upgrade to grass-6.4.0-4.fc14:
>> http://koji.fedoraproject.org/koji/buildinfo?buildID=263115
> Thanks I'll see if I can upgrade.
I upgraded to the 6.4.0 and the results are exactly the same.  The 
polygons really are identical in every respect except for they have 
different values in the cat column.  Is there some other grass tool for 
removing this kind of duplicate?
>> Markus
>>
>
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