NAME

       v.split  - Splits vector lines to shorter segments.

KEYWORDS

       vector, geometry, densification, node, segment, vertex

SYNOPSIS

       v.split
       v.split --help
       v.split  [-nf]  input=name   [layer=string]   output=name  [length=float]   [units=string]
       [vertices=integer]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -n
           Add new vertices, but do not split
           Applies only to ’length’ option

       -f
           Force segments to be exactly of given length, except for last one
           Applies only to ’length’ option

       --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 (’-1’ for all layers)
           A single vector map  can  be  connected  to  multiple  database  tables.  This  number
           determines  which  table  to  use.  When used with direct OGR access this is the layer
           name.
           Default: -1

       output=name [required]
           Name for output vector map

       length=float
           Maximum segment length

       units=string
           Length units
           Options: map, meters, kilometers, feet, surveyfeet, miles, nautmiles
           Default: map

       vertices=integer
           Maximum number of vertices in segment

DESCRIPTION

       v.split splits vector lines into shorter segments using a maximal distance between  nodes.
       The resulting length of all segments is expected to be equal and not higher than the given
       length parameter.

NOTES

       v.split does not change the layer, nor the category information, nor the  attribute  table
       links  of  the original file. It just splits each line in segments and attributes the same
       category to all segments of the same original line. As the attribute table  is  linked  to
       the  features  with their category as key, all segments originating from the same original
       line are linked to the same line in the original attribute table which is just  copied  to
       the new map.

   Notes on individual segment information
       When running v.to.db on a map produced by v.split, v.to.db will add length information for
       each segment in its respective attribute line, but since all  the  segments  of  the  same
       original line share the same attribute table line, it only gets updated once.

       To  obtain  the length of each segment, the user will have to attribute different category
       values to each of them. The best way to do this on a separate layer, using v.category
       v.category v_split op=add layer=2 output=v_split_2
       and then run the following commands on the new layer 2:
       v.db.addtable v_split_2 layer=2
       v.db.addcolumn map=v_split_2 column="length double precision" layer=2
       v.to.db map=v_split_2 type=line option=length columns=length units=meters layer=2
       To link the new segments in the new layer to the original segments, use:
       v.db.addcolumn map=v_split_2 layer=2 column="cat_1 int"
       v.to.db map=v_split_2 layer=2 option=query query_layer=1 query_column=cat columns=cat_1

EXAMPLES

       The examples are based on the North Carolina sample data location.

   Example 1: Inserting nodes to railroad lines map
       # extract one railroad line for this example
       v.extract input=railroads output=myrr cats=1
       # show line, category, direction (to find the beginning)
       g.region vector=myrr
       d.erase
       d.vect myrr display=shape,cat,dir
       # insert nodes at a distance not longer than 1000m
       v.split input=myrr output=myrr_split_1km length=1000
       d.vect myrr_split_1km display=shape,topo

       Note: In case that the vector line data are not polylines, generate first polylines as the
       second step, eg.:
       # join segments into polyline
       v.build.polylines input=myrr output=myrr_polylines
       # regenerate categories
       v.category input=myrr_polylines output=myrailroads option=add

   Example 2: Inserting vertices to railroad lines map
       Note: first run the two steps from example 1.
       # insert vertices at a distance not longer than 1000m
       v.split -n input=myrr output=myrr_split length=1000
       d.vect myrr_split display=shape,topo

SEE ALSO

        v.edit, v.build.polylines, v.to.points, v.segment

AUTHOR

       Radim Blazek

SOURCE CODE

       Available at: v.split source code (history)

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