1v.dissolve(1)                 Grass User's Manual                v.dissolve(1)
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NAME

6       v.dissolve   -  Dissolves  boundaries  between adjacent areas sharing a
7       common category number or attribute.
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KEYWORDS

10       vector, area, dissolve
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SYNOPSIS

13       v.dissolve
14       v.dissolve help
15       v.dissolve input=name  output=name   [layer=integer]    [column=string]
16       [--overwrite]  [--verbose]  [--quiet]
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18   Flags:
19       --overwrite
20           Allow output files to overwrite existing files
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22       --verbose
23           Verbose module output
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25       --quiet
26           Quiet module output
27
28   Parameters:
29       input=name
30           Name of input vector map
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32       output=name
33           Name for output vector map
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35       layer=integer
36           Layer number. If -1, all layers are extracted
37           Default: 1
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39       column=string
40           Name of column used to dissolve common boundaries
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DESCRIPTION

43       The  v.dissolve  module is used to merge adjacent areas in a vector map
44       which share the same  category  value.  The  resulting  merged  area(s)
45       retains  this category value. Optionally, a column can be defined which
46       is used to find adjacent polygons with identical attribute  for  common
47       boundary  dissolving.   GRASS defines a vector area as composite entity
48       consisting of a set of closed boundaries and a centroid. The  centroids
49       must contain a category number (see v.centroids), this number is linked
50       to area attributes and database  links.   Multiple  attributes  may  be
51       linked to a single vector entity through numbered fields referred to as
52       layers.  Refer to v.category for more details.
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54       Merging of areas can also be accomplished using  "v.extract  -d"  which
55       provides  some  additional  options.   In  fact, v.dissolve is simply a
56       front-end to that module. The use of the column parameter adds  a  call
57       to v.reclass before.
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59       (GRASS Shell Script)
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EXAMPLES

62   Basic use
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64       v.dissolve input=undissolved output=dissolved
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67   Dissolving based on column attributes
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69       # check column names:
70       v.info -c polbnda_italy
71       # dissolve based on column attributes:
72       v.dissolve input=polbnda_italy output=pol_italy_regions col=vmap_nam
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75   Dissolving adjacent SHAPE files to remove tile boundaries
76       If tile boundaries of adjacent maps (e.g. CORINE Landcover SHAPE files)
77       have to be removed, an extra step  is  required  to  remove  duplicated
78       boundaries:
79       # patch tiles after import:
80       v.patch     -e     `g.mlist     type=vect     pat="clc2000_*"    sep=,`
81       out=clc2000_patched
82       # remove duplicated tile boundaries:
83       v.clean   clc2000_patched   out=clc2000_clean    tool=snap,break,rmdupl
84       thresh=.01
85       # dissolve based on column attributes:
86       v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00
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SEE ALSO

90        v.category, v.centroids, v.extract, v.reclass
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AUTHORS

93       module:  M.  Hamish Bowman, Dept. Marine Science, Otago University, New
94       Zealand
95       Markus Neteler for column support
96       help page: Trevor Wiens
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98       Last changed: $Date: 2007-03-04 19:13:15 +0100 (Sun, 04 Mar 2007) $
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100       Full index
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102       © 2003-2008 GRASS Development Team
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106GRASS 6.3.0                                                      v.dissolve(1)