skyviewveg: Calculates a sky view correction factor underneath vegetation

In ilyamaclean/microclima: microclimate modelling with R

Calculates a sky view correction factor underneath vegetation

Description

skyviewveg is used to calculate a coefficient to correct for the proportion of sky obscured by topography when calculating net shortwave or longwave radiation above the canopy.

Usage

skyviewveg(dtm, l, x, steps = 36, reso = 1)

Arguments

dtm	a SpatRaster object, two-dimensional array or matrix of elevations (m).
l	a SpatRaster object, two-dimensional array or matrix of leaf area index values as returned by lai().
x	a SpatRaster object, two-dimensional array of numeric values representing the ratio of vertical to horizontal projections of leaf foliage as returned by leaf_geometry().
steps	an optional integer. The sky view is calculated from the horizon angle in specified directions. Steps defines the total number of directions used. If the default 36 is specified, then the horizon angle is calculated at 10º intervals.
reso	a single numeric value representing the spatial resolution of dtm (m).

Details

If dtm is a SpatRaster object, a SpatRaster object is returned. The projection system associated with dtm must be such that units of x, y and z are identical. Use terra::project() to convert the projection to a Universal Transverse Mercator type projection system. If a proportion of the sky of partially obscured, then the isotropic radiation flux received by a surface underneath canopy can be determined by integrating the single direction radiation transmission over the proportion of sky in view. This function returns a computationally efficient approximation of the integrated transmission over the proportion of sky in view expressed as a proportion of the integrated transmission over the entire hemisphere.

Value

a SpatRaster object or a two-dimensional array of numeric values representing the proportion of isotropic radiation received by a surface partially obscured by topography relative to the full hemisphere underneath vegetation.

See Also

The function skyviewtopo() calculates a sky view correction factor above vegetation.

Examples

library(terra)
l <- lai(aerial_image[,, 3], aerial_image[,, 4])
x <- leaf_geometry(rast(veg_hgt))
sv <- skyviewveg(rast(dtm1m), l, x)
plot(sv, main = "Sky view factor")

ilyamaclean/microclima documentation built on Sept. 5, 2024, 8:37 p.m.