Ubuntu Manpage: r.spread - Simulates elliptically anisotropic spread on a graphics window and generates a

NAME

       r.spread  - Simulates elliptically anisotropic spread on a graphics window and generates a
       raster map of the cumulative time of spread, given raster maps  containing  the  rates  of
       spread (ROS), the ROS directions and the spread origins.
       It  optionally produces raster maps to contain backlink UTM coordinates for tracing spread
       paths.

KEYWORDS

       raster, fire

SYNOPSIS

       r.spread
       r.spread help
       r.spread  [-vds]  max=string  dir=string  base=string   start=string    [spot_dist=string]
       [w_speed=string]      [f_mois=string]      [least_size=odd    int]     [comp_dens=decimal]
       [init_time=int   (>=   0)]     [lag=int   (>=   0)]     [backdrop=string]    output=string
       [x_output=string]   [y_output=string]   [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -v
           Run VERBOSELY

       -d
           DISPLAY 'live' spread process on screen

       -s
           For wildfires: consider SPOTTING effect

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       max=string
           Name of raster map containing MAX rate of spread (ROS) (cm/min)

       dir=string
           Name of raster map containing DIRections of max ROS (degree)

       base=string
           Name of raster map containing BASE ROS (cm/min)

       start=string
           Name of raster map containing STARTing sources

       spot_dist=string
           Name of raster map containing max SPOTting DISTance (m) (required w/ -s)

       w_speed=string
           Name of raster map containing midflame Wind SPEED (ft/min) (required w/ -s)

       f_mois=string
           Name  of  raster  map  containing  fine Fuel MOISture of the cell receiving a spotting
           firebrand (%) (required w/ -s)

       least_size=odd int
           Basic sampling window SIZE needed to meet certain accuracy (3)
           Options: 3,5,7,9,11,13,15

       comp_dens=decimal
           Sampling DENSity for additional COMPutin (range: 0.0 - 1.0 (0.5))

       init_time=int (>= 0)
           INITial TIME for current simulation (0) (min)

       lag=int (>= 0)
           Simulating time duration LAG (fill the region) (min)

       backdrop=string
           Name of raster map as a display backdrop

       output=string
           Name of raster map to contain OUTPUT spread time (min)

       x_output=string
           Name of raster map to contain X_BACK coordinates

       y_output=string
           Name of raster map to contain Y_BACK coordinates

DESCRIPTION

Spread phenomena usually show uneven movement over space. Such unevenness is due to two
reasons:
1) the uneven conditions from location to location, which can be called SPATIAL
HETEROGENEITY, and
2) the uneven conditions in different directions, which can be called ANISOTROPY.
The anisotropy of spread occurs when any of the determining factors have directional
components. For example, wind and topography cause anisotropic spread of wildfires.

One of the simplest spatial heterogeneous and anisotropic spread is elliptical spread, in
which, each local spread shape can be thought as an ellipse. In a raster setting, cell
centers are foci of the spread ellipses, and the spread phenomenon moves fastest toward
apogees and slowest to perigees. The sizes and shapes of spread ellipses may vary cell by
cell. So the overall spread shape is commonly not an ellipse.

r.spread simulates elliptically anisotropic spread phenomena, given three raster map
layers about ROS (base ROS, maximum ROS and direction of the maximum ROS) plus a raster
map layer showing the starting sources. These ROS layers define unique ellipses for all
cell locations in the current geographic region as if each cell center was a potential
spread origin. For some wildfire spread, these ROS layers can be generated by another
GRASS raster program r.ros. The actual locations reached by a spread event are constrained
by the actual spread origins and the elapsed spread time.

r.spread optionally produces raster maps to contain backlink UTM coordinates for each
raster cell of the spread time map. The spread paths can be accurately traced based on the
backlink information by another GRASS raster program r.spreadpath.

Part of the spotting function in r.spread is based on Chase (1984) and Rothermel (1983).
More information on r.spread, r.ros and r.spreadpath can be found in Xu (1994).

Flags:

       -v
               Run verbosely, printing information about program progress to standard output.

       -d
               Display the "live" simulation on screen. A graphics  window  must  be  opened  and
              selected before using this option.

       -s
               For wildfires, also consider spotting.

Parameters

max=name
Name of an existing raster map layer in the user's current mapset search path
containing the maximum ROS values (cm/minute).

dir=name
Name of an existing raster map layer in the user's current mapset search path
containing directions of the maximum ROSes, clockwise from north (degree).

base=name
Name of an existing raster map layer in the user's current mapset search path
containing the ROS values in the directions perpendicular to maximum ROSes'
(cm/minute). These ROSes are also the ones without the effect of directional
factors.

start=name
Name of an existing raster map layer in the user's current mapset search path
containing starting locations of the spread phenomenon. Any positive integers in
this map are recognized as starting sources.

spot_dist=name
Name of an existing raster map layer in the user's current mapset search path
containing the maximum potential spotting distances (meters).

w_speed=name
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).

f_mois=name
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).

least_size=odd int An odd integer ranging 3 - 15 indicating
the basic sampling window size within which all cells will be considered to see
whether they will be reached by the current spread cell. The default number is 3
which means a 3x3 window.

comp_dens=decimal A decimal number ranging 0.0 - 1.0 indicating
additional sampling cells will be considered to see whether they will be reached by
the current spread cell. The closer to 1.0 the decimal number is, the longer the
program will run and the higher the simulation accuracy will be. The default number
is 0.5.

init_time=int A non-negative number specifying the initial
time for the current spread simulation (minutes). This is useful when multiple
phase simulation is conducted. The default time is 0.

lag=int A non-negative integer specifying the simulating
duration time lag (minutes). The default is infinite, but the program will
terminate when the current geographic region/mask has been filled. It also controls
the computational time, the shorter the time lag, the faster the program will run.

backdrop=name
Name of an existing raster map layer in the user's current mapset search path to be
used as the background on which the "live" movement will be shown.

output=name
Name of the new raster map layer to contain the results of the cumulative spread
time needed for a phenomenon to reach each cell from the starting sources
(minutes).

x_output=name
Name of the new raster map layer to contain the results of backlink information in
UTM easting coordinates for each cell.

y_output=name
Name of the new raster map layer to contain the results of backlink information in
UTM northing coordinates for each cell.

OPTIONS

       The user can run r.spread either interactively or non- interactively. The program  is  run
       interactively  if  the  user types r.spread without specifying flag settings and parameter
       values on the command line. In this case, the user will be prompted for input.

       Alternately, the user can run r.spread  non-interactively,  by  specifying  the  names  of
       raster map layers and desired options on the command line, using the form:

       r.spread  [-vds]  max=name  dir=name  base=name start=name [spot_dist=name] [w_speed=name]
       [f_mois=name] [least_size=odds int] [comp_dens=decimal] [init_time=int (>=0)] [lag=int (>=
       0)]  [backdrop=name] output=name [x_output=name] [y_output=name] The -d option can only be
       used after a graphics window is opened and selected.

       Options spot_dist=name, w_speed=name and f_mois=name must all be given if the -s option is
       used.

EXAMPLE

       Assume  we  have  inputs,  the  following  simulates  a spotting- involved wildfire on the
       graphics window  and  generates  three  raster  maps  to  contain  spread  time,  backlink
       information in UTM northing and easting coordinates:

       r.spread   -ds   max=my_ros.max   dir=my_ros.maxdir   base=my_ros.base   start=fire_origin
       spot_dist=my_ros.spotdist w_speed=wind_speed  f_mois=1hour_moisture  backdrop=image_burned
       output=my_spread x_output=my_spread.x y_output=my_spread.y

NOTES

1. r.spread is a specific implementation of the shortest path algorithm. r.cost GRASS
program served as the starting point for the development of r.spread. One of the major
differences between the two programs is that r.cost only simulates ISOTROPIC spread while
r.spread can simulate ELLIPTICALLY ANISOTROPIC spread, including isotropic spread as a
special case.

2. Before running r.spread, the user should prepare the ROS (base, max and direction) maps
using appropriate models. For some wildfire spread, a separate GRASS program r.ros based
on Rothermel's fire equation does such work. The combination of the two forms a simulation
of wildfire spread.

3. The relationship of the start map and ROS maps should be logically correct, i.e. a
starting source (a positive value in the start map) should not be located in a spread
BARRIER (zero value in the ROS maps). Otherwise the program refuses to run.

4. r.spread uses the current geographic region settings. The output map layer will not go
outside the boundaries set in the region, and will not be influenced by starting sources
outside. So any change of the current region may influence the output. The recommendation
is to use slightly larger region than needed. Refer to g.region to set an appropriate
geographic region.

5. The inputs to r.spread should be in proper units.

6. r.spread is a computationally intensive program. The user may need to choose
appropriate size of the geographic region and resolution.

7. A low and medium (i.e. <= 0.5) sampling density can improve accuracy for elliptical
simulation significantly, without adding significantly extra running time. Further
increasing the sample density will not gain much accuracy while requiring greatly
additional running time.

REFERENCES

       Chase, 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.

       Rothermel, R. C., 1983, How to predict the spread and intensity of forest and range fires.
       US Forest Service, Gen. Tech. Rep. INT-143.  Ogden, Utah.

       Xu, Jianping, 1994, Simulating the spread of  wildfires  using  a  geographic  information
       system  and  remote  sensing,  Ph. D. Dissertation, Rutgers University, New Brunswick, New
       Jersey.

AUTHOR

       Jianping Xu and Richard G. Lathrop, Jr., Center for Remote Sensing and  Spatial  Analysis,
       Rutgers University.

       Last changed: $Date: 2006-04-13 12:25:42 -0700 (Thu, 13 Apr 2006) $

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