1r.spread(1) Grass User's Manual r.spread(1)
2
6 r.spread - Simulates elliptically anisotropic spread on a graphics
7 window and generates a raster map of the cumulative time of spread,
8 given raster maps containing the rates of spread (ROS), the ROS direc‐
9 tions and the spread origins.
10 It optionally produces raster maps to contain backlink UTM coordinates
11 for tracing spread paths.
12
14 raster
15
17 r.spread
18 r.spread help
19 r.spread [-vds] max=string dir=string base=string start=string
20 [spot_dist=string] [w_speed=string] [f_mois=string]
21 [least_size=odd int] [comp_dens=decimal] [init_time=int (>= 0)]
22 [lag=int (>= 0)] [backdrop=string] output=string [x_output=string]
23 [y_output=string] [--overwrite] [--verbose] [--quiet]
24 Flags:
26 -v
27 Run VERBOSELY
28 -d
30 DISPLAY 'live' spread process on screen
31 -s
33 For wildfires: consider SPOTTING effect
34 --overwrite
36 Allow output files to overwrite existing files
37 --verbose
39 Verbose module output
40 --quiet
42 Quiet module output
43 Parameters:
45 max=string
46 Name of raster map containing MAX rate of spread (ROS) (cm/min)
47 dir=string
49 Name of raster map containing DIRections of max ROS (degree)
50 base=string
52 Name of raster map containing BASE ROS (cm/min)
53 start=string
55 Name of raster map containing STARTing sources
56 spot_dist=string
58 Name of raster map containing max SPOTting DISTance (m) (required
59 w/ -s)
60 w_speed=string
62 Name of raster map containing midflame Wind SPEED (ft/min)
63 (required w/ -s)
64 f_mois=string
66 Name of raster map containing fine Fuel MOISture of the cell
67 receiving a spotting firebrand (%) (required w/ -s)
68 least_size=odd int
70 Basic sampling window SIZE needed to meet certain accuracy (3)
71 Options: 3,5,7,9,11,13,15
72 comp_dens=decimal
74 Sampling DENSity for additional COMPutin (range: 0.0 - 1.0 (0.5))
75 init_time=int (>= 0)
77 INITial TIME for current simulation (0) (min)
78 lag=int (>= 0)
80 Simulating time duration LAG (fill the region) (min)
81 backdrop=string
83 Name of raster map as a display backdrop
84 output=string
86 Name of raster map to contain OUTPUT spread time (min)
87 x_output=string
89 Name of raster map to contain X_BACK coordiates
90 y_output=string
92 Name of raster map to contain Y_BACK coordiates
93
95 Spread phenomena usually show uneven movement over space. Such uneven‐
96 ness is due to two reasons:
97 1) the uneven conditions from location to location, which can be called
98 SPATIAL HETEROGENEITY, and
99 2) the uneven conditions in different directions, which can be called
100 ANISOTROPY.
101 The anisotropy of spread occurs when any of the determining factors
102 have directional components. For example, wind and topography cause an‐
103 isotropic spread of wildfires.
104 One of the simplest spatial heterogeneous and anisotropic spread is
106 elliptical spread, in which, each local spread shape can be thought as
107 an ellipse. In a raster setting, cell centers are foci of the spread
108 ellipses, and the spread phenomenon moves fastest toward apogees and
109 slowest to perigees. The sizes and shapes of spread ellipses may vary
110 cell by cell. So the overall spread shape is commonly not an ellipse.
111 r.spread simulates elliptically anisotropic spread phenomena, given
113 three raster map layers about ROS (base ROS, maximum ROS and direction
114 of the maximum ROS) plus a raster map layer showing the starting
115 sources. These ROS layers define unique ellipses for all cell loca‐
116 tions in the current geographic region as if each cell center was a
117 potential spread origin. For some wildfire spread, these ROS layers
118 can be generated by another GRASS raster program r.ros. The actual
119 locations reached by a spread event are constrained by the actual
120 spread origins and the elapsed spread time.
121 r.spread optionally produces raster maps to contain backlink UTM coor‐
123 dinates for each raster cell of the spread time map. The spread paths
124 can be accurately traced based on the backlink information by another
125 GRASS raster program r.spreadpath.
126 Part of the spotting function in r.spread is based on Chase (1984) and
128 Rothermel (1983). More information on r.spread, r.ros and r.spreadpath
129 can be found in Xu (1994).
130
132 -v
133 Run verbosely, printing information about program progress to
134 standard output.
135 -d
137 Display the "live" simulation on screen. A graphics window must
138 be opened and selected before using this option.
139 -s
141 For wildfires, also consider spotting.
142
144 max=name
145 Name of an existing raster map layer in the user's current
146 mapset search path containing the maximum ROS values
147 (cm/minute).
148 dir=name
150 Name of an existing raster map layer in the user's current
151 mapset search path containing directions of the maximum ROSes,
152 clockwise from north (degree).
153 base=name
155 Name of an existing raster map layer in the user's current
156 mapset search path containing the ROS values in the directions
157 perpendicular to maximum ROSes' (cm/minute). These ROSes are
158 also the ones without the effect of directional factors.
159 start=name
161 Name of an existing raster map layer in the user's current
162 mapset search path containing starting locations of the spread
163 phenomenon. Any positive integers in this map are recognized as
164 starting sources.
165 spot_dist=name
167 Name of an existing raster map layer in the user's current
168 mapset search path containing the maximum potential spotting
169 distances (meters).
170 w_speed=name
172 Name of an existing raster map layer in the user's current
173 mapset search path containing wind velocities at half of the
174 average flame height (feet/minute).
175 f_mois=name
177 Name of an existing raster map layer in the user's current
178 mapset search path containing the 1-hour (<.25") fuel moisture
179 (percentage content multiplied by 100).
180 least_size=odd int An odd integer ranging 3 - 15 indicating
182 the basic sampling window size within which all cells will be
183 considered to see whether they will be reached by the current
184 spread cell. The default number is 3 which means a 3x3 window.
185 comp_dens=decimal A decimal number ranging 0.0 - 1.0 indicating
187 additional sampling cells will be considered to see whether they
188 will be reached by the current spread cell. The closer to 1.0
189 the decimal number is, the longer the program will run and the
190 higher the simulation accuracy will be. The default number is
191 0.5.
192 init_time=int A non-negative number specifying the initial
194 time for the current spread simulation (minutes). This is useful
195 when multiple phase simulation is conducted. The default time is
196 0.
197 lag=int A non-negative integer specifying the simulating
199 duration time lag (minutes). The default is infinite, but the
200 program will terminate when the current geographic region/mask
201 has been filled. It also controls the computational time, the
202 shorter the time lag, the faster the program will run.
203 backdrop=name
205 Name of an existing raster map layer in the user's current
206 mapset search path to be used as the background on which the
207 "live" movement will be shown.
208 output=name
210 Name of the new raster map layer to contain the results of the
211 cumulative spread time needed for a phenomenon to reach each
212 cell from the starting sources (minutes).
213 x_output=name
215 Name of the new raster map layer to contain the results of back‐
216 link information in UTM easting coordinates for each cell.
217 y_output=name
219 Name of the new raster map layer to contain the results of back‐
220 link information in UTM northing coordinates for each cell.
221
223 The user can run r.spread either interactively or non- interactively.
224 The program is run interactively if the user types r.spread without
225 specifying flag settings and parameter values on the command line. In
226 this case, the user will be prompted for input.
227 Alternately, the user can run r.spread non-interactively, by specifying
229 the names of raster map layers and desired options on the command line,
230 using the form:
231 r.spread [-vds] max=name dir=name base=name start=name [spot_dist=name]
233 [w_speed=name] [f_mois=name] [least_size=odds int] [comp_dens=decimal]
234 [init_time=int (>=0)] [lag=int (>= 0)] [backdrop=name] output=name
235 [x_output=name] [y_output=name] The -d option can only be used after a
236 graphics window is opened and selected.
237 Options spot_dist=name, w_speed=name and f_mois=name must all be given
239 if the -s option is used.
240
242 Assume we have inputs, the following simulates a spotting- involved
243 wildfire on the graphics window and generates three raster maps to con‐
244 tain spread time, backlink information in UTM northing and easting
245 coordinates:
246 r.spread -ds max=my_ros.max dir=my_ros.maxdir base=my_ros.base
248 start=fire_origin spot_dist=my_ros.spotdist w_speed=wind_speed
249 f_mois=1hour_moisture backdrop=image_burned output=my_spread x_out‐
250 put=my_spread.x y_output=my_spread.y
251
253 1. r.spread is a specific implementation of the shortest path algo‐
254 rithm. r.cost GRASS program served as the starting point for the
255 development of r.spread. One of the major differences between the two
256 programs is that r.cost only simulates ISOTROPIC spread while r.spread
257 can simulate ELLIPTICALLY ANISOTROPIC spread, including isotropic
258 spread as a special case.
259 2. Before running r.spread, the user should prepare the ROS (base, max
261 and direction) maps using appropriate models. For some wildfire spread,
262 a separate GRASS program r.ros based on Rothermel's fire equation does
263 such work. The combination of the two forms a simulation of wildfire
264 spread.
265 3. The relationship of the start map and ROS maps should be logically
267 correct, i.e. a starting source (a positive value in the start map)
268 should not be located in a spread BARRIER (zero value in the ROS maps).
269 Otherwise the program refuses to run.
270 4. r.spread uses the current geographic region settings. The output map
272 layer will not go outside the boundaries set in the region, and will
273 not be influenced by starting sources outside. So any change of the
274 current region may influence the output. The recommendation is to use
275 slightly larger region than needed. Refer to g.region to set an appro‐
276 priate geographic region.
277 5. The inputs to r.spread should be in proper units.
279 6. r.spread is a computationally intensive program. The user may need
281 to choose appropriate size of the geographic region and resolution.
282 7. A low and medium (i.e. <= 0.5) sampling density can improve accuracy
284 for elliptical simulation significantly, without adding significantly
285 extra running time. Further increasing the sample density will not gain
286 much accuracy while requiring greatly additional running time.
287
289 g.region, r.cost, r.spreadpath, r.ros
290
292 Chase, Carolyn, H., 1984, Spotting distance from wind-driven surface
293 fires -- extensions of equations for pocket calculators, US Forest Ser‐
294 vice, Res. Note INT-346, Ogden, Utah.
295 Rothermel, R. C., 1983, How to predict the spread and intensity of for‐
297 est and range fires. US Forest Service, Gen. Tech. Rep. INT-143.
298 Ogden, Utah.
299 Xu, Jianping, 1994, Simulating the spread of wildfires using a geo‐
301 graphic information system and remote sensing, Ph. D. Dissertation,
302 Rutgers University, New Brunswick, New Jersey.
303
305 Jianping Xu and Richard G. Lathrop, Jr., Center for Remote Sensing and
306 Spatial Analysis, Rutgers University.
307 Last changed: $Date: 2006-04-13 21:25:42 +0200 (Thu, 13 Apr 2006) $
309 Full index
311 © 2003-2008 GRASS Development Team
313GRASS 6.3.0 r.spread(1)