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

6       v.dissolve  - Dissolve boundaries between adjacent areas sharing a com‐
7       mon 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]
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18   Flags:
19       --overwrite
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21   Parameters:
22       input=name
23           Name of input vector map
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25       output=name
26           Name for output vector map
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28       layer=integer
29           Layer number. If -1, all layers are extracted Default: 1
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31       column=string
32           Name of column used to dissolve common boundaries
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DESCRIPTION

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

54   Basic use
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56       v.dissolve input=undissolved output=dissolved
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58
59   Dissolving based on column attributes
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61       # check column names:
62       v.info -c polbnda_italy
63       # dissolve based on column attributes:
64       v.dissolve input=polbnda_italy output=pol_italy_regions col=vmap_nam
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67   Dissolving adjacent SHAPE files to remove tile boundaries
68       If tile boundaries of adjacent maps (e.g. CORINE Landcover SHAPE files)
69       have to be removed, an extra step  is  required  to  remove  duplicated
70       boundaries:
71       # patch tiles after import:
72       v.patch     -e     `g.mlist     type=vect     pat="clc2000_*"    sep=,`
73       out=clc2000_patched
74       # remove duplicated tile boundaries:
75       v.clean   clc2000_patched   out=clc2000_clean    tool=snap,break,rmdupl
76       thresh=.01
77       # dissolve based on column attributes:
78       v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00
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SEE ALSO

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

85       module:  M.  Hamish Bowman, Dept. Marine Science, Otago University, New
86       Zealand
87       Markus Neteler for column support
88       help page: Trevor Wiens
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90       Last changed: $Date: 2007/05/24 07:59:56 $
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92       Full index
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96GRASS 6.2.2                                                      v.dissolve(1)