v.dissolve - Dissolves boundaries between adjacent areas sharing a
common category number or attribute.
vector, area, dissolve
v.dissolve input=name output=name [layer=integer] [column=string]
[--overwrite] [--verbose] [--quiet]
Allow output files to overwrite existing files
Verbose module output
Quiet module output
Name of input vector map
Name for output vector map
Layer number. If -1, all layers are extracted.
A single vector map can be connected to multiple database tables.
This number determines which table to use.
Name of column used to dissolve common boundaries
The v.dissolve module is used to merge adjacent areas in a vector map
which share the same category value. The resulting merged area(s)
retains this category value. Alternatively an integer or string column
can be defined which is used to find adjacent polygons with identical
attribute for common boundary dissolving. In this case the categories
are not retained, only the values of the new key column. See the
v.reclass help page for details.
GRASS defines a vector area as composite entity consisting of a set of
closed boundaries and a centroid. The centroids must contain a category
number (see v.centroids), this number is linked to area attributes and
Multiple attributes may be linked to a single vector entity through
numbered fields referred to as layers. Refer to v.category for more
Merging of areas can also be accomplished using v.extract -d which
provides some additional options. In fact, v.dissolve is simply a
front-end to that module. The use of the column parameter adds a call
to v.reclass before.
v.dissolve input=undissolved output=dissolved
Dissolving based on column attributes
North Carolina data set:
v.dissolve mysoils_general output=mysoils_general_families
Dissolving adjacent SHAPE files to remove tile boundaries
If tile boundaries of adjacent maps (e.g. CORINE Landcover SHAPE files)
have to be removed, an extra step is required to remove duplicated
# patch tiles after import:
v.patch -e `g.mlist type=vect pat="clc2000_*" sep=","`
# remove duplicated tile boundaries:
v.clean clc2000_patched out=clc2000_clean tool=snap,break,rmdupl
# dissolve based on column attributes:
v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00
v.category, v.centroids, v.extract, v.reclass
module: M. Hamish Bowman, Dept. Marine Science, Otago University, New
Markus Neteler for column support
help page: Trevor Wiens
Last changed: $Date: 2011-09-04 06:23:30 -0700 (Sun, 04 Sep 2011) $
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