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.
Message: 1
Date: Thu, 20 Aug 2009 09:44:34 +0930
From: Sharon M <morrisxs09@gmail.com>
Subject: [GRASS-user] attribute info attached to multiple areas
To: grass-user@lists.osgeo.org
Message-ID:
<7a0cde410908191714ja3439dbw36f1c112428157ca@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.
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.
Message: 1
Date: Thu, 20 Aug 2009 09:44:34 +0930
From: Sharon M <morrisxs09@gmail.com>
Subject: [GRASS-user] attribute info attached to multiple areas
To: grass-user@lists.osgeo.org
Message-ID:
<7a0cde410908191714ja3439dbw36f1c112428157ca@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.