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NAME

r.lfp - Calculates the longest flow path for a given outlet point using the r.stream.distance addon.

KEYWORDS

hydrology, watershed

SYNOPSIS

r.lfp
r.lfp --help
r.lfp input=name output=name coordinates=east,north [--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 drainage direction raster map
output=name [required]
Name for output longest flow path raster map
coordinates=east,north [required]
Coordinates of outlet point

Table of contents

DESCRIPTION

r.lfp calculates the longest flow path for a given outlet point and creates a new raster map with a thin line representing the longest flow path. This module requires the r.stream.distance addon.

NOTES

r.lfp creates a longest flow path raster map using a drainage direction raster map and the coordinates of an outlet point. The module internally runs r.stream.distance twice to calculate flow length downstream and upstream raster maps, and combines them to get the longest flow path. An input drainage map can be created using r.watershed or r.stream.extract.

EXAMPLES

Workflow example

r.watershed elevation=elev drainage=drain
r.water.outlet input=drain output=basin coordinates=-888857.11,1117788.38
r.lfp input=drain output=lfp coordinates=-888857.11,1117788.38

North Carolina sample dataset example

# set computational region
g.region raster=elevation -p

# calculate drainage directions
r.watershed elevation=elevation drainage=drain_directions

# calculate outlet point related watershed
r.water.outlet input=drain_directions output=basin coordinates=642455,222614

# calculate longest flow path
r.lfp input=drain_directions output=lfp coordinates=642455,222614

SEE ALSO

v.lfp, r.watershed, r.stream.extract, r.stream.distance
How to calculate the longest flow path in GRASS GIS

AUTHOR

Huidae Cho

Last changed: $Date: 2017-03-11 07:31:12 +0100 (Sat, 11 Mar 2017) $

SOURCE CODE

Available at: r.lfp source code (history)


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© 2003-2017 GRASS Development Team, GRASS GIS 7.2.3svn Reference Manual