Point Patterns of New Brunswick Forest Fires

Description

Point patterns created from yearly records, provided by the New Brunswick Department of Natural Resources, of all fires falling under their jurisdiction for the years 1987 to 2003 inclusive (with the year 1988 omitted until further notice).

Usage

data(nbfires)

Format

Executing data(nbfires) creates three objects: nbfires, nbextras, and nbw.rect.

The object nbfires is a marked point pattern (an object of class "ppp") consisting of all of the fires in the years 1987 to 2003 inclusive, with the omission of 1988. The marks consist of the last two digits of the years, with the string nbfires. prepended. Patterns for individual years can be extracted using the function split.ppp(). (See ``Examples''.)

The object nbextras is a list of data frames, with names extras.87, ..., extras.03. The columns of these data frames provide ``extra'' information about the fires. (See ``Details''.)

The object nbw.rect is a rectangular window which covers central New Brunswick. It is provided for use in illustrative and ``practice'' calculations inasmuch as the use of a rectangular window simplifies some computations considerably.

Details

The coordinates of the fire locations were provided in terms of latitude and longitude, to the nearest minute of arc. These were converted to New Brunswick stereographic projection coordinates (Thomson, Mephan and Steeves, 1977) which was the coordinate system in which the map of New Brunswick — which constitutes the observation window for the pattern — was obtained. The conversion was done using a C program kindly provided by Jonathan Beaudoin of the Department of Geodesy and Geomatics, University of New Brunswick.

Finally the data and window were rescaled since the use of the New Brunswick stereographic projection coordinate system resulted in having to deal with coordinates which are expressed as very large integers with a bewildering number of digits. Amongst other things, these huge numbers tended to create very untidy axis labels on graphs. The width of the bounding box of the window was made equal to 1000 (nameless) units. In addition the lower left hand corner of this bounding box was shifted to the origin. The height of the bounding box was changed proportionately, resulting in a value of approximately 959.

The window for the fire patterns comprises 6 polygonal components, consisting of mainland New Brunswick and the 5 largest islands. Some lakes which should form holes in the mainland component are currently missing; this problem will be remedied in future releases. The window was formed by ``simplifying'' the map that was originally obtained. The simplification consisted in reducing (using an interactive visual technique) the number of polygon edges in each component. For instance the number of edges in the mainland component was reduced from over 138,000 to 500.

For some purposes it is probably better to use a discretized (mask type) window. See ``Examples''.

Because of the coarseness of the coordinates of the original data (1 minute of longitude is approximately 1 kilometer at the latitude of New Brunswick), data entry errors, and the simplification of the observation window, many of the original fire locations appeared to be outside of the window. This problem was addressed by shifting the location of the ``outsider'' points slightly, or deleting them, as seemed appropriate.

The columns of the data frames comprising nbextras are

fire.type
A code for the type of fire with 1 = forest, 2 = grass, 3 = dump, and 4 = other.
dis.date
The discovery date of the fire, which is the nearest possible surrogate for the start date of the fire. These columns are of class Date and have the format yyyy-mm-dd
dis.time
The discovery time (time of day) of the fire, on a 24 hour clock. These columns are of mode character and have the format HH:MM.
dis.julian
The discovery date and time of the fire, expressed in ``Julian days'', i.e. as a decimal fraction representing the number of days since the beginning of the year (midnight 31 December).
out.date
The date on which the fire was judged to be ``out''.
out.time
The time of day on a 24 hour clock, at which the fire was judged to be ``out''.
out.julian
The date and time at which the fire was judged to be ``out'', expressed in Julian days.
cause
General cause of the fire, coded as 1 = railroads, 2 = unknown, 3 = miscellaneous, 4 = lightening, 5 = forest industry, 6 = incendiary, 7 = recreation, 8 = resident, 9 = other industry. Causes 2, 4, and 6 are designated as ``final'' by the New Brunswick Department of Natural Resources, meaning (it seems) ``that's all there is to it''. Other causes are apparently intended to be refined by being combined with ``source of ignition''.
ign.src
Source of ignition, coded as 1 = cigarette/match/pipe/ashes, 2 = burning without a permit, 3 = burning with a permit, 4 = prescribed burn, 5 = wood spark, 6 = machine spark, 7 = campfire, 8 = chainsaw, 9 = machinery, 10 = vehicle accident, 11 = railroad accident, 12 = wheelbox on railcars, 13 = hot flakes off railcar wheels, 14 = dump (i.e. fire escaping from a dump), 15 = ashes (briquettes, burning garbage, etc.)
fnl.size
The final size of the fire (area burned) in hectares, to the nearest 10th hectare.

Note that due to data entry errors some of the ``out dates'' and ``out times'' in the original data sets were actually earlier than the corresponding ``discovery dates'' and ``discover times''. In such cases all corresponding entries of the extras data frame (i.e. dis.date, dis.time, dis.julian, out.date, out.time, and out.julian) were set equal to NA. Also, some of the dates and times were missing (equal to NA) in the original data sets.

Source

The data were kindly provided by the New Brunswick Department of Natural Resources. Special thanks are due to Jefferey Betts for a great deal of assistance.

References

Turner, Rolf (2007) Point patterns of forest fire locations. To appear in Environmental and Ecological Statistics.

Thomson, D. B., Mephan, M. P., and Steeves, R. R. (1977) The stereographic double projection. Technical Report 46, University of New Brunswick, Fredericton, N. B., Canada URL: gge.unb.ca/Pubs/Pubs.html.

Examples

## Not run: 
data(nbfires)
X <- split(nbfires) # Create a list of yearly point patterns.
attach(X)           # Make the individual point patterns accessible.
attach(nbextras)    # Make the individual `extras' accessible.
ftyp <- extras.00$fire.type
Y.00 <- nbfires.00[ftyp==1 | ftyp==2] # Pick out forest and grass fires.
stt  <- extras.00$dis.julian[ftyp==1 | ftyp==2] 
fin  <- extras.00$out.julian[ftyp==1 | ftyp==2] 
Y.00 <- setmarks(Y.00,fin-stt) # Mark the pattern with fire duration.
plot(Y.00)
#
nbw.mask <- as.mask(nbfires$window, dimyx=500)
plot(nbw.mask, col=c("green", "white"))
plot(nbfires$window, border="red", add=TRUE)
#
plot(unmark(Y.00)[nbw.rect], add=TRUE)
plot(nbw.rect,add=TRUE,border="blue")
#
K.00 <- Kest(Y.00)
plot(K.00)
## End(Not run)