Geografic-Information-System/raster/r.ros/r.ros.html

<h2>DESCRIPTION</h2>

<em>r.ros</em> generates the base ROS value, maximum ROS value, direction
of the maximum ROS, and optionally the maximum potential spotting distance
of a wildfire for each raster cell in the current geographic region. 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 Laboratory,
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 calculated by a
separate function, spot_dist(), which is based on Lathrop and Xu (in preparation),
Chase (1984) and Rothermel (1991). These three or four raster map layers
serve as inputs for another GRASS raster program r.spread. More information
on r.ros and r.spread can be found in Xu (1994).

<h3>Parameters</h3>
<dl>
<dt><b>model</b>
<dd> 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.

<dt><b>moisture_1h</b>
<dd> Name of an existing raster map layer in
the user's current mapset search path containing the 1-hour (&lt;.25&quot;)
fuel moisture (percentage content multiplied by 100).

<dt><b>moisture_10h</b> 
<dd>Name of an existing raster map layer in the
user's current mapset search path containing the 10-hour (.25-1&quot;) fuel
moisture (percentage content multiplied by 100).

<dt><b>moisture_100h</b>
<dd>Name of an existing raster map layer in the
user's current mapset search path containing the 100-hour (1-3&quot;) fuel moisture
(percentage content multiplied by 100).

<dt><b>moisture_live</b>
<dd>Name of an existing raster map layer in the
user's current mapset search path containing live (herbaceous) fuel fuel
moisture (percentage content multiplied by 100).

<dt><b>velocity</b>
<dd>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).

<dt><b>direction</b>
<dd>Name of an existing raster map
layer in the user's current mapset search path containing wind direction,
clockwise from north (degree).

<dt><b>slope</b>
<dd>Name of
an existing raster map layer in the user's current mapset search path containing
topographic slope (degree).

<dt><b>aspect</b>
<dd>Name of an existing
raster map layer in the user's current mapset search path containing
topographic aspect, counter-clockwise from east (GRASS convention)
(degree).

<dt><b>elevation</b>
<dd>Name of an existing raster map
layer in the user's current mapset search path containing elevation (meters).

<dt><b>output</b>
<dd>Prefix of new
raster map layers in the user's current mapset to contain
<br> 1) the base (perpendicular) ROS
(cm/minute);
<br> 2) the maximum (forward) ROS (cm/minute),
<br> 3) the direction of the maximum
ROS, clockwise from north (degree), and optionally
<br> 4) the maximum potential
spotting distance (meters).
<br>If 'my_ros' is given as the output name, then r.ros automatically
assigns 'my_ros.base', 'my_ros.max', 'my_ros.maxdir', and optionally,
'my_ros.spotdist' as the names for the actual output map layers.
</dl>

<h3>OPTIONS</h3>

<p>If the options <b>moisture_1h</b>, <b>moisture_10h</b>, and
<b>moisture_100h</b> are partially given, the program will assign
values to the missing option using the formula:

<div class="code"><pre>
moisture_100h = moisture_10h + 1 = moisture_1h + 2.
</pre></div>

However at least one of them should be given. Options <b>velocity</b>
and <b>direction</b> must be in pair, whether given or not. If none is
given, the program will assume a no-wind
condition. Options <b>slope</b> and <b>aspect</b> must be in pair,
whether given or not. If none is given, the program will assume a
topographically flat condition. Option
<b>elevation</b> must be given if <b>-s</b> option is used.

<h2>EXAMPLES</h2>
Assume we have inputs, the following generates ROSes and spotting distances:

<div class="code"><pre>
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=my_ros
</pre></div>

<h2>NOTES</h2>

<ol>
  <li>r.ros is supposed to be run before running another GRASS program r.spread.
    The combination of the two forms a simulation of the spread of wildfires.
  <li>The inputs to r.ros should be in proper units.
  <li>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 maximum ROS would result in
    calculation failure in the r.spread program.
  <li>The user needs to provide only ONE output name even the program
    actually generates THREE or FOUR map layers.
  <li>The rules for optional parameters must be followed.
</ol>

<h2>REFERENCES</h2>

<ul>
  <li><b>Albini,</b> F. A., 1976, Computer-based models of wildland fire behavior:
    a user's manual, USDA Forest Service, Intermountain Forest and Range Experiment
    Station, Ogden, Utah.
  <li><b>Andrews</b>, 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.
  <li><b>Chase</b>, Carolyn, H., 1984, Spotting distance from wind-driven
    surface fires -- extensions of equations for pocket calculators, US Forest
    Service, Res. Note INT-346, Ogden, Utah.
  <li><b>Lathrop</b>, Richard G. and Jianping Xu, A geographic information
    system-based approach for calculating spotting distance. (in preparation)
  <li><b>Rothermel</b>, R. E., 1972, A mathematical model for predicting
    fire spread in wildland fuels, USDA Forest Service, Intermountain Forest
    and Range Experiment Station, Res. Pap. INT-115, Ogden, Utah.
  <li><b>Rothermel</b>, Richard, 1991, Predicting behavior and size of crown
    fires in the northern Rocky Mountains, US Forest Service, Res. Paper INT-438,
    Ogden, Utah.
  <li><b>Xu</b>, Jianping, 1994, Simulating the spread of wildfires using
    a geographic information system and remote sensing, Ph. D. Dissertation,
    Rutgers University, New Brunswick, New Jersey.
</ul>

<h2>SEE ALSO</h2>

<em>
  <a href="g.region.html">g.region</a>,
  <a href="r.slope.aspect.html">r.slope.aspect</a>,
  <a href="r.spread.html">r.spread</a>
</em>

<h2> AUTHOR</h2>

Jianping Xu, Center for Remote Sensing and Spatial Analysis, Rutgers University.

<p><i>Last changed: $Date$</i>