v.split(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

✨ v.split ✨

okay bestie, this is the GRASS GIS User's Manual page for v.split(1) and it is literally the tool that chops your long vector lines into lil bite-sized segments 💅

💖 NAME 💖

v.split — splits vector lines to shorter segments. it's giving ✂️ for your geometry, no cap.

🌸 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 — adds new vertices but does not split. heads up: this only applies to the length option.
  • -f — forces segments to be exactly the given length, except for the last one. also only applies to the length option.
  • --overwrite — lets your output files overwrite files that already exist 👀
  • --help — prints the usage summary
  • --verbose — verbose module output, if you want the tea ☕
  • --quiet — quiet module output, if you want silence 🤫
  • --ui — forces the GUI dialog to launch

🍓 Parameters 🍓

  • input=name [required] — name of input vector map. can also be a 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, and 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 🌈

so 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. periodt. 💖

💜 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 into segments and gives the same category to all segments of the same original line. and because the attribute table is linked to the features with their category as key, all segments coming from the same original line are linked to the same line in the original attribute table — which is just copied over to the new map. iconic behaviour, honestly. 🫶

🧚 Notes on individual segment information 🧚

when you run 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, you'll have to attribute different category values to each of them. the best way to do this is 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 🔥

these examples are based on the North Carolina sample data. let's go 🚂

⭐ 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)

accessed: Saturday Jan 17 05:41:28 2026

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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

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