[GRASS-dev] vector dissolve problems

Dylan Beaudette dylan.beaudette at gmail.com
Fri Nov 10 11:50:25 EST 2006

Hi Markus,

This is a feature that would be very helpful to have in GRASS. Until
my adventures with PostGIS, I would have to resort to using Arc-*** to
perform this sort of "dissolve". While this functionality is simple to
use in PostGIS, dissolve operations on VERY large datasets can be time

Here is a relevant thread on the topic:



On 11/10/06, Markus Neteler <neteler at itc.it> wrote:
> Hi,
> I try to merge the 100km tiles of the CORINE vector
> landcover maps which are delivered in SHAPE format.
> Due to the tiling there are annoying boundaries now
> when patching the tiles together. I then tried to
> reclass and dissolve them based on the landuse
> code to no avail.
> Procedure:
> for i in E43N26 E44N26 E45N26 E43N25 E44N25 E45N25
> do
>  unzip /cdrom/data/clc00/100km$i.zip
>  v.in.ogr 100km$i.shp out=clc2000_$i
> done
> v.patch -e `g.mlist type=vect pat="clc2000_*" sep=,` out=clc2000_tn_bl
> # break tile boundaries:
> v.clean clc2000_tn_bl out=clc2000_tn_bl_clean tool=break
> # reclass to landuse code:
> v.reclass clc2000_tn_bl_clean out=clc2000_tn_bl_recl col=CODE_00
> # dissolve
> v.extract -d clc2000_tn_bl_recl out=clc2000_tn_bl_dissolved
> The resulting map remains essentially unchanged:
> http://mpa.itc.it/markus/tmp/vect_dissolve_troubles.png
> Manual removal in v.digit works. But since I have 700 tiles...
> Any ideas?
> Markus
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