Crown classification point cloud — classify_crown

Returns the crown points from a tree point cloud.

Usage

classify_crown_pc(
  pc,
  thresholdbranch = 1.5,
  minheight = 1,
  buttress = FALSE,
  thresholdR2 = 0.001,
  slice_thickness = 0.06,
  thresholdbuttress = 0.001,
  maxbuttressheight = 7,
  concavity = 4,
  dtm = NA,
  r = 5,
  plot = FALSE,
  plotcolors = c("#08aa7c", "#fac87f")
)

Arguments

pc: The tree point cloud as a data.frame with columns X,Y,Z. Output of read_tree_pc.
thresholdbranch: Numeric value (default=1.5) that is multiplied with the diameter of the tree (calculated with dbh_pc or dab_pc when buttress =TRUE) which determines the cutt-off where a branch emerges and the crown begins.
minheight: Numeric value (default=1) with the minimum height at which the crown begins. Should be above the widest part of the buttresses for buttressed trees (value of 4 is recommended). For non-buttressed trees choose a lower value (such as 1).
buttress: Logical (default=FALSE), indicates if the trees have buttresses (higher than breast height).
thresholdR2: Numeric value (default=0.001). Parameter of the dbh_pc function used to calculate the diameter at breast height. Only relevant when buttress == FALSE.
slice_thickness: Numeric value (default = 0.06). Parameter of the dbh_pc function used to calculate the diameter at breast height. Only relevant when buttress == FALSE.
thresholdbuttress: Numeric value (default=0.001). Parameter of the dab_pc function used to calculate the diameter above buttresses. Only relevant when buttress == TRUE.
maxbuttressheight: Numeric value (default=7). Parameter of the dab_pc function used to calculate the diameter at breast height. Only relevant when buttress == TRUE.
concavity: Numeric value (default=4) concavity for the computation of the functional diameter using a concave hull based on concaveman.
dtm: The digital terrain model as a data.frame with columns X,Y,Z (default = NA). If the digital terrain model is in the same format as a point cloud it can also be read with read_tree_pc.
r: Numeric value (default=5) r which determines the range taken for the dtm. Should be at least the resolution of the dtm. Only relevant when a dtm is provided.
plot: Logical (default=FALSE), indicates if the classified tree is plotted.
plotcolors: list of two colors for plotting. Only relevant when plot = TRUE. The crown and trunk are colored by the first and second element of this list respectively.

Value

List with data.frame with the crown point cloud (part of the tree above the first branch) in crownpoints and data.frame with the trunk point cloud in trunkpoints. Also optionally (plot=TRUE) plots the crown vs non-crown points and in this case returns a list with the crown point cloud as first element, trunk point clouds as a second element and the plots as the third to fifth elements.

Details

The classification is based on the increased distance between the minimum and maximum X (and Y) coordinates of the tree points within a horizontal slice when the first branch is reached with increasing height. When the bottom of the point cloud is incomplete or obstructed you can choose to add a digital terrain model as an input which is used to estimate lowest point of the point cloud in order to obtain slices at the correct height of the tree.

Examples

if (FALSE) {
# Read tree point cloud and extract the crown points
pc_tree <- read_tree_pc(PC_path = "path/to/point_cloud.txt")
crown_pc <- classify_crown_pc(pc = pc_tree)
# and plot the classification results
output <- classify_crown_pc(pc = pc_tree, plot = TRUE)
crown_pc <- output$crownpoints
# with non-default settings for a buttressed tree
crown_pc <- classify_crown_pc(pc = pc_tree, minheight = 4, buttress = TRUE)
}