cffdrs (version 1.8.20)

lros: Line-based input for Simard Rate of Spread and Direction

Description

lros is used to calculate the rate of spread and direction given one set of three point-based observations of fire arrival time. The function requires that the user specify the time that the fire crossed each point, along with the measured lengths between each pair of observational points, and a reference bearing (one specified side of the triangle). This function allows quick input of a dataframe specifying one or many triangles.

Usage

lros(input)

Value

lros returns a dataframe which includes the rate of spread and spread direction. Output units depend on the user’s inputs for distance (typically meters) and time (seconds or minutes).

Arguments

input

A dataframe containing input variables of time fire front crossed points 1, 2, 3, and latitude/longitude for those same points. Variable names have to be the same as in the following list, but they are case insensitive. The order in which the input variables are entered is not important.

T1	(required)	Time that the fire front crossed point 1. Time entered in fractional
		format. Output ROS will depend on the level of precision entered
		(minute, second, decisecond)
T2	(required)	Time that the fire front crossed point 2. Time entered in fractional
		format. Output ROS will depend on the level of precision entered
		(minute, second, decisecond)
T3	(required)	Time that the fire front crossed point 3. Time entered in fractional
		format. Output ROS will depend on the level of precision entered
		(minute, second, decisecond)
LengthT1T2	(required)	Length between each pair of observation points T1 and T2 (subscripts
		denote time-ordered pairs). (meters)
LengthT2T3	(required)	Length between each pair of observation points T2 and T3 (subscripts
		denote time-ordered pairs). (meters)
LengthT1T3	(required)	Length between each pair of observation points T1 and T3 (subscripts
		denote time-ordered pairs). (meters)
BearingT1T2	(required)	Reference bearing. For reference, North = 0, West = -90, East = 90 (degrees)
BearingT1T3	(required)	Reference bearing. For reference, North = 0, West = -90, East = 90 (degrees)

Author

Tom Schiks, Xianli Wang, Alan Cantin

Details

lros Allows R users to calculate the rate of spread and direction of a fire across a triangle, given three time measurements and details about the orientation and distance between observational points. The algorithm is based on the description from Simard et al. (1984). See pros for more information.

The functions require the user to arrange the input dataframe so that each triangle of interest is identified based on a new row in the dataframe. The input format forces the user to identify the triangles, one triangle per row of input dataframe. Very complex arrangements of field plot layouts are possible, and the current version of these functions do not attempt to determine each triangle of interest automatically.

References

1. Simard, A.J., Eenigenburg, J.E., Adams, K.B., Nissen, R.L., Deacon, and Deacon, A.G. 1984. A general procedure for sampling and analyzing wildland fire spread.

2. Byram, G.M. 1959. Combustion of forest fuels. In: Davis, K.P. Forest Fire Control and Use. McGraw-Hill, New York.

3. Curry, J.R., and Fons, W.L. 1938. Rate of spread of surface fires in the Ponderosa Pine Type of California. Journal of Agricultural Research 57(4): 239-267.

4. Simard, A.J., Deacon, A.G., and Adams, K.B. 1982. Nondirectional sampling wildland fire spread. Fire Technology: 221-228.

See Also

pros,

Examples

library(cffdrs)
# manual single entry, but converted to a data frame
lros.in1 <- data.frame(t(c(0, 24.5, 50, 22.6, 120, 20.0, 90, 35)))
colnames(lros.in1)<-c("T1","LengthT1T2", "T2", "LengthT1T3", "T3", 
                      "LengthT2T3", "bearingT1T2", "bearingT1T3")
lros.out1 <- lros(lros.in1)
lros.out1

# multiple entries using a dataframe
# load the test dataframe for lros
data("test_lros")
lros(test_lros)