View source: R/radiationtools.R
skyviewtopo | R Documentation |
skyviewtopo
is used to calculate a coefficient to correct for the proportion of sky in view when calculating net shortwave or longwave radiation above the canopy.
skyviewtopo(dtm, steps = 36, reso = 100)
dtm |
dtm a SpatRaster object, two-dimensional array or matrix of elevations (m). |
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 |
If a proportion of the sky of partially obscured, then the isotropic radiation flux received by a surface can be determined by integrating the single direction radiation flux over the proportion of sky in view. This function returns the integrated flux over the proportion of sky in view expressed as a proportion of the integrated flux over the entire hemisphere.
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.
a SpatRaster object or two-dimension array of values representing the proportion of isotropic radiation received by a partially obscured surface relative to the full hemisphere.
The function skyviewveg()
calculates a sky view correction factor underneath vegetation.
library(terra)
sv <- skyviewtopo(rast(dtm100m))
plot(sv, main = "Sky view factor")
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