Returns the tree height measured from a tree point cloud. If a digital terrain model (dtm) is provided it is used to estimate the tree height.
Usage
tree_height_pc(
pc,
dtm = NA,
r = 5,
plot = FALSE,
plotcolors = c("#000000", "#08aa7c", "#fac87f")
)Arguments
- pc
The tree point cloud as a data.frame with columns X,Y,Z. Output of
read_tree_pc.- 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 tree point cloud is plotted.
- plotcolors
list of three colors for plotting. Only relevant when plot = TRUE. The tree points, the lowest point height and the DTM points are colored by the first, second and third element of this list respectively.
Value
List with the tree height (numeric value) and the determined lowest point (lp, numeric value). Also optionally (plot=TRUE) plots the tree point cloud and in this case returns a list with the tree height as first element, the lowest point as the second element and the plots as third, fourth and fifth elements.
Details
The tree height is measured as the difference between the Z-value of the highest and lowest point of the tree point cloud. The lowest point of a tree point cloud is sometimes not sampled (e.g. for low density UAV-LS, in dense forests). In this case, a dtm can be provided and will be used to estimate the lowest point: this is the height of the dtm under the tree point cloud, which is calculated as the median Z-value of the digital terrain model points within a horizontal (x,y-)range (r) of the 10 lowest points of the tree point cloud.
Examples
if (FALSE) {
# Read tree point cloud and calculate the tree height
pc_tree <- read_tree_pc(PC_path = "path/to/point_cloud.txt")
tree_height <- tree_height_pc(pc = pc_tree)
# Read the digital terrain model
dtm <- read_tree_pc(PC_path = "path/to/dtm.txt")
# Calculate the tree height based on the point cloud and dtm
tree_height <- tree_height_pc(pc = pc_tree, dtm = dtm, r = 1)
}