divide_plot: Divides one ore more plots into subplots

In BIOMASS: Estimating Aboveground Biomass and Its Uncertainty in Tropical Forests

Divides one ore more plots into subplots

Description

This function divides a plot (or several plots) into subplots in the relative coordinates system, and returns the coordinates of subplot corners.

Usage

divide_plot(
  corner_data,
  rel_coord,
  proj_coord = NULL,
  longlat = NULL,
  grid_size,
  grid_tol = 0.1,
  origin = NULL,
  tree_data = NULL,
  tree_coords = NULL,
  corner_plot_ID = NULL,
  tree_plot_ID = NULL,
  sd_coord = NULL,
  n = 100
)

Arguments

corner_data	A data frame, data frame extension, containing the plot corner coordinates. Typically, the output ⁠$corner_coord⁠ of the check_plot_coord() function.
rel_coord	A character vector of length 2, specifying the column names (resp. x, y) of the corner relative coordinates.
proj_coord	(optional, if longlat is not provided) A character vector of length 2, specifying the column names (resp. x, y) of the corner projected coordinates.
longlat	(optional, if proj_coord is not provided) A character vector of length 2, specifying the column names of the corner geographic coordinates (long,lat).
grid_size	A vector indicating the dimensions of grid cells (resp. X and Y dimensions). If only one value is given, grid cells will be considered as squares.
grid_tol	A numeric between (0;1) corresponding to the percentage of the plot area allowed to be excluded from the plot division (when grid_size doesn't match exactly plot dimensions).
origin	Alignment of the subplot grid, based on relative coordinates. If NULL (default), the grid is aligned to the origin corner of the relative coordinates. Alternatively provide a numeric vector of length 2, specifying the relative coordinates to which the grid should be aligned. This option is especially useful when grid_size doesn't match exactly plot dimensions.
tree_data	A data frame containing tree relative coordinates and other optional tree metrics (one row per tree).
tree_coords	A character vector of length 2, specifying the column names of the relative coordinates of the trees.
corner_plot_ID	If dealing with several plots: a vector indicating plot IDs for corners.
tree_plot_ID	If dealing with several plots: a vector indicating tree plot IDs.
sd_coord	used to propagate GPS measurements uncertainties to the subplot polygon areas and the ref_raster footprint in subplot_summary(). See Details.
n	used to propagate GPS measurements uncertainties: the number of iterations to be used (as in AGBmonteCarlo()). Cannot be smaller than 50 or larger than 1000.

Details

If corner coordinates in the projected coordinate system are provided (proj_coord), projected coordinates of subplot corners are calculated by a bilinear interpolation in relation with relative coordinates of plot corners. Be aware that this bilinear interpolation only works if the plot in the relative coordinates system is rectangular (ie, has 4 right angles).

In order to propagate GPS measurement uncertainties, the sd_coord argument has to be provided and must contains the average standard deviation of the GPS measurements for each corner on the X and Y axes (typically, the output $sd_coord of the check_plot_coord() function). If corner_data contains only one plot, sd_coord must be a numeric. If dealing with several plot, sd_coord must be a data frame of two columns named 'plot_ID' and 'sd_coord' containing respectively the plot IDs and the previous metric (again, see the output $sd_coord of the check_plot_coord() function).

Value

Returns a list containing:

• $sub_corner_coord: a data-frame containing as many rows as there are corners corresponding to the subplots, and the following columns :

  • plot_ID: If dealing with multiple plots: the plot code, else, a column containing an empty character

  • subplot_ID: The automatically generated subplot code, using the following rule : subplot_X_Y

  • x_rel and y_rel : the relative X-axis and Y-axis coordinates of subplots corners.

  • x_proj and y_proj : if proj_coord is provided, the projected X-axis and Y-axis coordinates of subplots corners

• $tree_data: the tree_data argument with the subplot_ID of each tree in the last column

• $UTM_code: if 'longlat' is provided, a data.frame containing the UTM code of the corner GPS coordinates for each plot

• $simu_coord: if sd_coord is provided, a list of n data-tables containing the simulated coordinates

Author(s)

Arthur PERE, Arthur BAILLY, John L. GODLEE

Examples

# One plot with repeated measurements of each corner
data("NouraguesPlot201")
check_plot201 <- check_plot_coord(
  corner_data = NouraguesPlot201,
  proj_coord = c("Xutm","Yutm"), rel_coord = c("Xfield","Yfield"),
  trust_GPS_corners = TRUE, draw_plot = FALSE)
subplots_201 <- divide_plot(
  corner_data = check_plot201$corner_coord, 
  rel_coord = c("x_rel","y_rel"), proj_coord = c("x_proj","y_proj"),
  grid_size = 50)
subplots_201

# Assigning trees to subplots
data("NouraguesTrees")
plot201_trees <- NouraguesTrees[NouraguesTrees$Plot == 201,]
subplots_201 <- suppressWarnings(
  divide_plot(
    corner_data = check_plot201$corner_coord, 
    rel_coord = c("x_rel","y_rel"), proj_coord = c("x_proj","y_proj"),
    grid_size = 50,
    tree_data = plot201_trees, tree_coords = c("Xfield","Yfield")))
head(subplots_201$sub_corner_coord)
head(subplots_201$tree_data)

# When grid dimensions (40m x 40m) don't fit perfectly plot dimensions
# an origin at (10 ; 10) will center the grid

  divide_plot(
    corner_data = check_plot201$corner_coord, 
    rel_coord = c("x_rel","y_rel"),
    grid_size = c(40,40),
    grid_tol = 0.4,
    origin = c(10,10)
 )


# Dealing with multiple plots
data("NouraguesCoords")
nouragues_subplots <- suppressWarnings(
  divide_plot(
    corner_data = NouraguesCoords,
    rel_coord = c("Xfield","Yfield"), proj_coord = c("Xutm","Yutm"),
    corner_plot_ID = "Plot",
    grid_size = 50,
    tree_data = NouraguesTrees, tree_coords =  c("Xfield","Yfield"),
    tree_plot_ID = "Plot"))
head(nouragues_subplots$sub_corner_coord)
head(nouragues_subplots$tree_data)

BIOMASS documentation built on March 11, 2026, 9:08 a.m.