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 maximum 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 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). More information 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
blackforest_ros.base
, blackforest_ros.max
,
blackforest_ros.maxdir
,
and (optionally) blackforest_ros.spotdist
raster maps.
If only one or two of the options moisture_1h, moisture_10h, and moisture_100h are given, the module will assign values to the missing option using the formula:
moisture_100h = moisture_10h + 1 = moisture_1h + 2
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.
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