h_visibility: Compute horizontal visibility

In Blecigne/viewshed3d: Compute Viewshed in 3D Point Clouds of Ecosystems

Compute horizontal visibility

Description

Computes the horizontal visibility in a viewshed defined as a disk.

Usage

h_visibility(
  data,
  position = c(0, 0, 0),
  layer_tickness = 0.1,
  angular_res = 1,
  scene_radius
)

Arguments

data	LAS class object containing the xyz coordinates of a 3D point cloud.
position	vector of length 3 containing the xyz coordinates of the animal location. Default = c(0,0,0).
layer_tickness	numeric. The thickness of the disk that defines the viewshed.
angular_res	numeric. The angular resolution of a single sightline. Default = 1.
scene_radius	(optional) numeric. Defines the radius of the scene relative to the animal position. Can be used to apply a cut-off distance to visibility analyses.

Value

A list containing a data.table of the visibility ($visibility) as a function of distance to the animal location (r), a data.table of the viewshed ($viewshed) defined as the radius (r) for each azimuth (phi) with non occluded sightlines distance set to scene_radius, a data.table ($vegetation_distance) of the vegetation distance (r) in each azimuth (phi) for occluded sightlines only and different viewshed metrics ($metrics). The metrics are: the viewshed fractal dimension (computed from Chen, 2020), the viewshed area (i.e. the visible area), the proportion visible (the area visible / potential area visible), the viewshed coefficient (the area under the curve of visibility as a function of distance) and the vegetation fractal dimension.

References

Chen, Y. (2020). Two Sets of Simple Formulae to Estimating Fractal Dimension of Irregular Boundaries. Mathematical Problems in Engineering, 2020. https://doi.org/10.1155/2020/7528703

Examples

#- import the tree_line_plot dataset
file <- system.file("extdata", "tree_line_plot.laz", package="viewshed3d")
tls <- lidR::readLAS(file)

center <- c(0,0,2) # defines the scene center for the entire process
angle <- 1 # defines the angular resolution for the entire process

#- remove noise to avoid visibility estimates error
tls_clean <- viewshed3d::denoise_scene(tls,method="sd",
                                       filter=6)

#- compute the horizontal visibility.
view.data <- viewshed3d::h_visibility(data = tls_clean,
                                      position = center,
                                      angular_res = angle,
                                      scene_radius = 17)

# viewshed metrics
view.data$metrics

# plot the view sheds in a radial plot
plotrix::radial.plot(view.data$viewshed$r,rp.type = "p",poly.col = "blue",
                     radial.lim = c(0,max(view.data$viewshed$r)))

Blecigne/viewshed3d documentation built on Nov. 5, 2022, 9:08 p.m.