r.ros(1grass) GRASS GIS User's Manual r.ros(1grass)
NAME
r.ros - Generates rate of spread raster maps.
Generates three, or four raster map layers showing the base (perpendic-
ular) rate of spread (ROS), the maximum (forward) ROS, the direction of
the maximum ROS, and optionally the maximum potential spotting distance
for fire spread simulation.
KEYWORDS
raster, fire, spread, rate of spread, hazard, model
SYNOPSIS
r.ros
r.ros --help
r.ros model=name [moisture_1h=name] [moisture_10h=name] [mois-
ture_100h=name] moisture_live=name [velocity=name] [direction=name]
[slope=name] [aspect=name] [elevation=name] base_ros=name
max_ros=name direction_ros=name [spotting_distance=name] [--over-
write] [--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:
model=name [required]
Raster map containing fuel models
Name of an existing raster map layer in the user’s current mapset
search path containing the standard fuel models defined by the USDA
Forest Service. Valid values are 1-13; other numbers are recognized
as barriers by r.ros.
moisture_1h=name
Raster map containing the 1-hour fuel moisture (%)
Name of an existing raster map layer in the user’s current mapset
search path containing the 1-hour (<.25") fuel moisture (percentage
content multiplied by 100).
moisture_10h=name
Raster map containing the 10-hour fuel moisture (%)
Name of an existing raster map layer in the user’s current mapset
search path containing the 10-hour (.25-1") fuel moisture (percent-
age content multiplied by 100).
moisture_100h=name
Raster map containing the 100-hour fuel moisture (%)
Name of an existing raster map layer in the user’s current mapset
search path containing the 100-hour (1-3") fuel moisture (percent-
age content multiplied by 100).
moisture_live=name [required]
Raster map containing live fuel moisture (%)
Name of an existing raster map layer in the user’s current mapset
search path containing live (herbaceous) fuel moisture (percentage
content multiplied by 100).
velocity=name
Raster map containing midflame wind velocities (ft/min)
Name of an existing raster map layer in the user’s current mapset
search path containing wind velocities at half of the average flame
height (feet/minute).
direction=name
Name of raster map containing wind directions (degree)
Name of an existing raster map layer in the user’s current mapset
search path containing wind direction, clockwise from north (de-
gree).
slope=name
Name of raster map containing slope (degree)
Name of an existing raster map layer in the user’s current mapset
search path containing topographic slope (degree).
aspect=name
Raster map containing aspect (degree, CCW from E)
Name of an existing raster map layer in the user’s current mapset
search path containing topographic aspect, counterclockwise from
east (GRASS convention) in degrees.
elevation=name
Raster map containing elevation (m, required for spotting)
Name of an existing raster map layer in the user’s current mapset
search path containing elevation (meters). Option is required from
spotting distance computation (when spotting_distance option is
provided)
base_ros=name [required]
Output raster map containing base ROS (cm/min)
Base (perpendicular) rate of spread (ROS)
max_ros=name [required]
Output raster map containing maximal ROS (cm/min)
The maximum (forward) rate of spread (ROS)
direction_ros=name [required]
Output raster map containing directions of maximal ROS (degree)
The direction of the maximal (forward) rate of spread (ROS)
spotting_distance=name
Output raster map containing maximal spotting distance (m)
The maximal potential spotting distance (requires elevation raster
map to be provided).
DESCRIPTION
r.ros is part of the wildfire simulation toolset. Preparational steps
for the fire simulation are the calculation of the rate of spread (ROS)
with r.ros, and the creating of spread map with r.spread. Eventually,
the fire path(s) based on starting point(s) are calculated with
r.spreadpath.
r.ros is used for fire (wildfire) modeling. The input is fuel model and
moisture and the outputs are rate of spread (ROS) values. The module
generates the base ROS value, maximum ROS value, direction of the maxi-
mum ROS, and optionally the maximum potential spotting distance of
wildfire for each raster cell in the current geographic region. These
three or four raster map layers serve as inputs for the r.spread module
which is the next step in fire simulation.
The r.ros module and two related modules r.spread, and r.spreadpath can
be used not only for wildfire modeling but also generally to simulate
other events where spread of something is involved and elliptical
spread is appropriate.
The calculation of the two ROS values for each raster cell is based on
the Fortran code by Pat Andrews (1983) of the Northern Forest Fire Lab-
oratory, USDA Forest Service. The direction of the maximum ROS results
from the vector addition of the forward ROS in wind direction and that
in upslope direction. The spotting distance, if required, will be cal-
culated by a separate function, spot_dist(), which is based on Lathrop
and Xu (in preparation), Chase (1984) and Rothermel (1991). More in-
formation on r.ros and r.spread can be found in Xu (1994).
The output parameter is a basename (prefix) for all generated raster
maps and each map gets a unique suffix:
• .base for the base (perpendicular) ROS (cm/minute)
• .max for the maximum (forward) ROS (cm/minute),
• .maxdir for the direction of the maximum ROS, clockwise from
north (degree), and optionally
• .spotdist for the maximum potential spotting distance (meters).
So, if the output parameter is blackforest_ros, r.ros creates blackfor-
est_ros.base, blackforest_ros.max, blackforest_ros.maxdir, and (option-
ally) blackforest_ros.spotdist raster maps.
If only one or two of the options moisture_1h, moisture_10h, and mois-
ture_100h are given, the module will assign values to the missing op-
tion using the formula:
moisture_100h = moisture_10h + 1 = moisture_1h + 2
However, at least one of them should be given.
Options velocity and direction must be both given or both omitted. If
none is given, the module will assume a no-wind condition.
Options slope and aspect must be also given together. If none is
given, the module will assume a topographically flat condition. Option
elevation must be given if -s (spotting) flag is used.
EXAMPLES
Assume we have inputs, the following generates ROSes and spotting dis-
tances:
r.ros -s model=fire_model moisture_1h=1hour_moisture moisture_live=live_moisture \
velocity=wind_speed direction=wind_direction \
slope=slope aspect=aspect elevation=elevation output=ros
NOTES
1 r.ros is supposed to be run before running r.spread module. The
combination of these two modules forms a simulation of the
spread of wildfires.
2 The user should be sure that the inputs to r.ros are in proper
units.
3 The output units for the base and maximum ROSes are in cm/minute
rather than ft/minute, which is due to that a possible zero
ft/minute base ROS value and a positive integer ft/minute maxi-
mum ROS would result in calculation failure in the r.spread mod-
ule. As far as the user just use r.ros together with r.spread,
there is no need to concern about these output units.
REFERENCES
• Albini, F. A., 1976, Computer-based models of wildland fire be-
havior: a user’s manual, USDA Forest Service, Intermountain
Forest and Range Experiment Station, Ogden, Utah.
• Andrews, P. L., 1986, BEHAVE: fire behavior prediction and fuel
modeling system -- BURN subsystem, Part 1, USDA Forest Service,
Intermountain Research Station, Gen. Tech. Rep. INT-194, Ogden,
Utah.
• Chase, Carolyn, H., 1984, Spotting distance from wind-driven
surface fires -- extensions of equations for pocket calcula-
tors, US Forest Service, Res. Note INT-346, Ogden, Utah.
• Lathrop, Richard G. and Jianping Xu, A geographic information
system-based approach for calculating spotting distance. (in
preparation)
• Rothermel, R. E., 1972, A mathematical model for predicting
fire spread in wildland fuels, USDA Forest Service, Intermoun-
tain Forest and Range Experiment Station, Res. Pap. INT-115,
Ogden, Utah.
• Rothermel, Richard, 1991, Predicting behavior and size of crown
fires in the northern Rocky Mountains, US Forest Service, Res.
Paper INT-438, Ogden, Utah.
• Xu, Jianping, 1994, Simulating the spread of wildfires using a
geographic information system and remote sensing, Ph. D. Dis-
sertation, Rutgers University, New Brunswick, Jersey (ref).
SEE ALSO
g.region, r.slope.aspect, r.spread, r.spreadpath Sample data download:
firedemo.sh (run this script within the "Fire simulation data set" lo-
cation.
AUTHOR
Jianping Xu, Center for Remote Sensing and Spatial Analysis, Rutgers
University.
SOURCE CODE
Available at: r.ros source code (history)
Accessed: unknown
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GRASS 7.8.7 r.ros(1grass)
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