v.lrs.create(1)

📦

version 8.4.2 · 9 versions

💖 v.lrs.create — the GRASS GIS manual, but make it make sense 💖

okay bestie, pull up a chair because we're diving into v.lrs.create(1) from the GRASS GIS User's Manual and honestly? it's giving main character energy for linear reference systems. no cap. 🦋

✨ NAME ✨

v.lrs.create — creates a linear reference system. that's it. that's the whole job. slay. 💅

🌈 KEYWORDS 🌈

vector, linear reference system, network. iykyk. 🎀

⭐ SYNOPSIS ⭐

here's the vibe check on how you actually call it, verbatim:

v.lrs.create
v.lrs.create --help
v.lrs.create in_lines=name out_lines=name  [err=name]  points=name
[llayer=string]   [player=string]  lidcol=string pidcol=string
[start_mp=string]   [start_off=string]   [end_mp=string]
[end_off=string]   [rsdriver=string]   [rsdatabase=string]
rstable=string  [threshold=float]   [--overwrite]  [--help]  [--verbose]
[--quiet]  [--ui]

🎀 Flags 🎀

the little switches, the accessories of the command line. each one is iconic in its own way:

--overwrite — allow output files to overwrite existing files. yes she will absolutely replace things, so be aware bestie 🙈
--help — print usage summary. your girl when you're lost.
--verbose — verbose module output. it will tell you everything, and honestly? we love a chatty icon 💬
--quiet — quiet module output. the introvert setting.
--ui — force launching GUI dialog. for when you want buttons instead of typing. no judgment 🫶

🌸 Parameters 🌸

okay now the real ones. the parameters. read carefully, bestie, because the required ones are required fr fr:

in_lines=name [required] — name of input vector map. this is the input vector map containing lines. 🌈
out_lines=name [required] — output vector map where oriented lines are written. the glow-up version of your lines ✨
err=name — output vector map of errors. yes, there's a whole map for the oopsies. she's honest like that 💀
points=name [required] — name of input vector map. it's the input vector map containing reference points 📍
llayer=string — layer number or name. it's the line layer. Default: 1
player=string — layer number or name. it's the point layer. Default: 1
lidcol=string [required] — column containing line identifiers for lines 🎯
pidcol=string [required] — column containing line identifiers for points 🎯
start_mp=string — column containing milepost position for the beginning of next segment. Default: start_mp
start_off=string — column containing offset from milepost for the beginning of next segment. Default: start_off
end_mp=string — column containing milepost position for the end of previous segment. Default: end_mp
end_off=string — column containing offset from milepost for the end of previous segment. Default: end_off
rsdriver=string — driver name for reference system table. Options: dbf, mesql, mysql, odbc, ogr, pg, sqlite. Default: sqlite
rsdatabase=string — database name for reference system table. Default: $GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db
rstable=string [required] — name of table where the reference system will be written. heads up: a new table is created by this module 🆕
threshold=float — maximum distance of point to line allowed. Default: 1

💜 DESCRIPTION 💜

v.lrs.create generates a LRS (Linear Reference System) from vector line and point data. so like, lines + points = a whole reference system. chemistry. 🧪✨

and listen — it is highly recommended to work with polylines instead of segmented vector lines. the command v.build.polylines creates this map structure. do it. trust. 🙏

🦋 NOTES 🦋

okay important deets, don't skip these:

the mileposts (point) vector map columns start_mp, start_off, end_mp, end_off must be of 'double precision' type. non-negotiable bestie, the type has to match or it's not gonna work 😭
for milepost ordering, it is sufficient to enter increasing numbers into the start_mp column indicating the order along the vector line. basically just count up and the order sorts itself out 📈
the lidcol and pidcol columns contain the line IDs which relate mileposts and vector line(s) to each other. it's the matching key, the situationship glue 💞
when creating a LRS with this module, any existing rstable will be replaced. not merged, not appended — replaced. so if you had something there, it's gone-gone 💀

🌟 EXAMPLE 🌟

this example is written for the Spearfish dataset. periodt.

🌸 Step one: bus route data prep 🌸

as first step, bus route data are prepared.

# break into segments for correct route selection
v.clean roads_net out=busroute_tmp tool=break
# make polyline for easier line selection by coordinate pairs
v.build.polylines busroute_tmp out=busroute_tmp2
# reverse delete: reduce route map to bus route (enter in one line)
v.edit -r busroute_tmp2 tool=delete coords=590273,4927304,\
590346,4927246,590414,4927210,590438,4927096,590468,4926966,\
590491,4926848,590566,4926798,590637,4926753,590701,4926698,\
590830,4926726,590935,4926751,590993,4926830,590972,4926949,\
590948,4927066,590922,4927182,590957,4927251 threshold=5
# vector line needs to be polyline
v.build.polylines busroute_tmp2 out=busroute_tmp3
v.category busroute_tmp3 out=busroute op=add
g.remove -f type=vector name=busroute_tmp,busroute_tmp2,busroute_tmp3

the result can be visualized:

g.region vector=busroute n=n+100 s=s-100 w=w-100 e=e+100
d.mon x0
d.vect roads_net
d.vect busroute col=red width=2

the vector map 'busroute' needs have an attribute table which contain an integer column lidcol with value be '22' for this example (bus route):

v.db.addtable busroute col="lid integer"
v.db.update busroute col=lid value=22
v.db.select busroute

and the output is literally:

cat|lid
1|22

a new point map 'busstops' shall contain mileposts (bus stops) along this line (use thresh to define maximal accepted deviation from this line):

# generate points map
echo "590263|4927361
590432|4927120
590505|4926776
590660|4926687
590905|4926742
590972|4926949
591019|4927263" | v.in.ascii out=busstops
d.vect busstops icon=basic/triangle col=blue
d.vect busstops disp=cat lcol=blue

the milepost attributes table needs to be created with specific columns:

v.db.addtable busstops col="lid integer, start_mp double precision, \
                   start_off double precision, end_mp double precision, \
                   end_off double precision"
v.db.update busstops col=lid value=22

since the digitizing order of v.in.ascii above reflects the bus stop order along the route, we can simply copy the category number as milepost order number in column start_mp:

v.db.update busstops col=start_mp qcol=cat
# verify table
v.db.select busstops

which gives you:

cat|lid|start_mp|start_off|end_mp|end_off
1|22|1|||
2|22|2|||
3|22|3|||
4|22|4|||
5|22|5|||
6|22|6|||
7|22|7|||

then visualize with start_mp to check the order:

d.erase
d.vect roads_net
d.vect busroute col=red width=2
d.vect busstops icon=basic/triangle col=blue
d.vect busstops disp=attr attrcol=start_mp lcol=blue

offsets (start_off, end_off) can be later used in case the route or mileposts get modified. future-proofing, we love to see it 💅

🎀 Step two: build the linear reference network 🎀

as second step, the linear reference network is created:

v.lrs.create busroute points=busstops out=route_lrs err=lrs_error \
             lidcol=lid pidcol=lid rstable=route_lrs threshold=50

this creates the maps 'route_lrs' containing the LRS and 'lrs_error' containing the errors if any. the resulting LRS table and map can be shown:

# show LRS table
db.select table=route_lrs
d.vect route_lrs col=blue width=2

and that's the whole glow-up. ✨

🔥 SEE ALSO 🔥

your recommended reading, bestie:

v.build.polylines
v.lrs.segment
v.lrs.where
v.lrs.label

also: the LRS tutorial, and Introducing the Linear Reference System in GRASS. go read, you'll be obsessed 📚💖

👑 AUTHORS 👑

Radim Blazek, ITC-irst/MPA Solutions
Documentation update (based on above journal article and available fragments): Markus Neteler

🧚 SOURCE CODE 🧚

Available at: v.lrs.create source code (history)

Accessed: Saturday Jan 17 05:41:24 2026

and that's the whole page, bestie 💖 big love to the GRASS Development Team for the © 2003-2025 and for shipping this as part of the GRASS GIS 8.4.2 Reference Manual — this page was accessed Saturday Jan 17 05:41:24 2026, and you read it just now, so consider yourself caught up 🫶✨ no cap, go build that LRS. 🎀

📦 where this page comes from

fedora 44: grass 8.4.2-4.fc44 · GPL-2.0-or-later
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-18: a language model's rewrite of the original, under its terms