find_bulk_density.r

# This program lets you manually enter the fuel mass for a scan, along with the 
# path to that scan. It calculates the bulk density of that scan and prints it 
# to the console in grams per cubic meter.

require("lidR")

# ENTER THE MASS OF THE FUEL HERE BEFORE RUNNING!
fuel.mass <- 738.24

# load the scan
las <- readLAS("C:/Users/js81535/Desktop/lidar_exploration/auto_clipped_scans/ambient_cones_rep1_autoclipped_pre.las")

# classify noise points and trim them
las <- classify_noise(las, sor(k=10, m=8))
las <- filter_poi(las, Classification != 18)

# classify ground and non-ground points
mycsf <- csf(FALSE, class_threshold = 0.009, rigidness = 3)
las <- classify_ground(las, mycsf)

# normalize heights from the ground and plot the scan
norm.las <- normalize_height(las, tin())

# rasterize the top of the fuel bed
fuel.raster <- rasterize_canopy(norm.las, res = 0.004, algorithm = dsmtin())
plot(fuel.raster)

# get all of the individual pixels in the raster
fuel.matrix <- as.matrix(fuel.raster)

# make an empty list. Then, populate it with the volumes for each pixel
uprights <- c()
for (point in fuel.matrix) {
  # we only want points that have positive height
  if (!is.na(point) && point > 0) {
    upright.volume <- point * 0.000016    # multiply by the area of each pixel (which is the resolution squared)
    uprights <- append(uprights, upright.volume)      
  }
}
total.volume <- sum(uprights)

bulk.density <- fuel.mass / total.volume

print(bulk.density)