v.lrs.create(1grass)

NAME
v.lrs.create - Creates a linear reference system.

KEYWORDS
vector, linear reference system, network

SYNOPSIS
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:

--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:

in_lines=name [required]
    Name of input vector map
    Input vector map containing lines

out_lines=name [required]
    Output vector map where oriented lines are written

err=name
    Output vector map of errors

points=name [required]
    Name of input vector map
    Input vector map containing reference points

llayer=string
    Layer number or name
    Line layer
    Default: 1

player=string
    Layer number or name
    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, 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
    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.

It is highly recommended to work with polylines instead of segmented vector lines. The command v.build.polylines creates this map structure.

NOTES
The mileposts (point) vector map columns start_mp, start_off, end_mp, end_off must be of ’double precision’ type. For milepost ordering, it is sufficient to enter increasing numbers into the start_mp column indicating the order along the vector line.

The lidcol and pidcol columns contain the line IDs which relate mileposts and vector line(s) to each other.

When creating a LRS with this module, any existing rstable will be replaced.

EXAMPLE
This example is written for the Spearfish dataset.

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
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
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|||
# visualize with start_mp to check 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.

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

SEE ALSO
v.build.polylines, v.lrs.segment, v.lrs.where, v.lrs.label

LRS tutorial,
Introducing the Linear Reference System in GRASS

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: Friday Apr 04 01:20:22 2025

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