1v.dissolve(1) GRASS GIS User's Manual v.dissolve(1)
2
6 v.dissolve - Dissolves boundaries between adjacent areas sharing a
7 common category number or attribute.
8
10 vector, dissolve, area, line
11
13 v.dissolve
14 v.dissolve --help
15 v.dissolve input=name [layer=string] [column=name] output=name
16 [--overwrite] [--help] [--verbose] [--quiet] [--ui]
17 Flags:
19 --overwrite
20 Allow output files to overwrite existing files
21 --help
23 Print usage summary
24 --verbose
26 Verbose module output
27 --quiet
29 Quiet module output
30 --ui
32 Force launching GUI dialog
33 Parameters:
35 input=name [required]
36 Name of input vector map
37 Or data source for direct OGR access
38 layer=string
40 Layer number or name.
41 Vector features can have category values in different layers. This
42 number determines which layer to use. When used with direct OGR ac‐
43 cess this is the layer name.
44 Default: 1
45 column=name
47 Name of attribute column used to dissolve common boundaries
48 output=name [required]
50 Name for output vector map
51
53 The v.dissolve module is used to merge adjacent areas in a vector map
54 which share the same category value. The resulting merged area(s) re‐
55 tains this category value. Alternatively an integer or string column
56 can be defined which is used to find adjacent polygons with identical
57 attribute for common boundary dissolving. In this case the categories
58 are not retained, only the values of the new key column. See the v.re‐
59 class help page for details.
60
62 GRASS defines a vector area as composite entity consisting of a set of
63 closed boundaries and a centroid. The centroids must contain a category
64 number (see v.centroids), this number is linked to area attributes and
65 database links.
66 Multiple attributes may be linked to a single vector entity through
68 numbered fields referred to as layers. Refer to v.category for more de‐
69 tails.
70 Merging of areas can also be accomplished using v.extract -d which pro‐
72 vides some additional options. In fact, v.dissolve is simply a
73 front-end to that module. The use of the column parameter adds a call
74 to v.reclass before.
75
77 Basic use
78 v.dissolve input=undissolved output=dissolved
79 Dissolving based on column attributes
81 North Carolina data set:
82 g.copy vect=soils_general,mysoils_general
83 v.dissolve mysoils_general output=mysoils_general_families column=GSL_NAME
84 Dissolving adjacent SHAPE files to remove tile boundaries
86 If tile boundaries of adjacent maps (e.g. CORINE Landcover SHAPE files)
87 have to be removed, an extra step is required to remove duplicated
88 boundaries:
89 # patch tiles after import:
90 v.patch -e `g.list type=vector pat="clc2000_*" separator=","` out=clc2000_patched
91 # remove duplicated tile boundaries:
92 v.clean clc2000_patched out=clc2000_clean tool=snap,break,rmdupl thresh=.01
93 # dissolve based on column attributes:
94 v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00
95
97 v.category, v.centroids, v.extract, v.reclass
98
100 module: M. Hamish Bowman, Dept. Marine Science, Otago University, New
101 Zealand
102 Markus Neteler for column support
103 help page: Trevor Wiens
104
106 Available at: v.dissolve source code (history)
107 Accessed: Saturday Jan 21 20:41:02 2023
109 Main index | Vector index | Topics index | Keywords index | Graphical
111 index | Full index
112 © 2003-2023 GRASS Development Team, GRASS GIS 8.2.1 Reference Manual
114GRASS 8.2.1 v.dissolve(1)