NAME

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

KEYWORDS

       vector, dissolve, area, line

SYNOPSIS

       v.dissolve
       v.dissolve --help
       v.dissolve  input=name  [layer=string]   [column=name]  output=name  [--overwrite]  [--help]  [--verbose]
       [--quiet]  [--ui]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input vector map
           Or data source for direct OGR access

       layer=string
           Layer number or name.
           Vector features can have category values in different layers. This number determines which  layer  to
           use. When used with direct OGR access this is the layer name.
           Default: 1

       column=name
           Name of attribute column used to dissolve common boundaries

       output=name [required]
           Name for output vector map

DESCRIPTION

       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.

NOTES

       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 database links.

       Multiple  attributes  may  be  linked  to  a  single vector entity through numbered fields referred to as
       layers. Refer to v.category for more details.

       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.

EXAMPLES

   Basic use
       v.dissolve input=undissolved output=dissolved

   Dissolving based on column attributes
       North Carolina data set:
       g.copy vect=soils_general,mysoils_general
       v.dissolve mysoils_general output=mysoils_general_families column=GSL_NAME

   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 boundaries:
       # patch tiles after import:
       v.patch -e `g.list type=vector pat="clc2000_*" separator=","` out=clc2000_patched
       # remove duplicated tile boundaries:
       v.clean clc2000_patched out=clc2000_clean tool=snap,break,rmdupl thresh=.01
       # dissolve based on column attributes:
       v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00

SEE ALSO

        v.category, v.centroids, v.extract, v.reclass

AUTHORS

       module: M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
       Markus Neteler for column support
       help page: Trevor Wiens

SOURCE CODE

       Available at: v.dissolve source code (history)

       Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual