solarIncidenceAngle: Compute solar incidence angle

In environmentalinformatics-marburg/satelliteTools: What the package does (short line)

Description

Compute the solar incidence angle over non-planar surfaces following the equation from Duffie and Beckman (2013).

Usage

## S4 method for signature 'POSIXt'
solarIncidenceAngle(x, dem, formula = c("Cooper",
  "Spencer"), neighbors = 8L, unit = c("radians", "degrees"))

## S4 method for signature 'character'
solarIncidenceAngle(x, dem, formula = c("Cooper",
  "Spencer"), neighbors = 8L, unit = c("radians", "degrees"), ...)

## S4 method for signature 'Raster'
solarIncidenceAngle(x, origin = strptime("1993-01-01",
  "%Y-%m-%d"), dem, formula = c("Cooper", "Spencer"), neighbors = 8L,
  unit = c("radians", "degrees"), ...)

Arguments

x	A date-time object of class POSIX*, or a character object that can be coerced by strptime, or a Raster* object holding such information.
dem	RasterLayer, digital elevation model in EPSG:4326 (see http://spatialreference.org/ref/epsg/wgs-84/).
formula	character, formula from which to calculate the angular declination of the sun, see declination.
neighbors	integer, number of focal cells from which to calculate surface slope and aspect, see terrain.
unit	character, determines whether to return the solar incidence angle in radians (default) or degrees.
...	If x is a character object, formatting arguments passed on to strptime, or if x is a Raster* object, formatting arguments related with the specified origin.
origin	A POSIX* or character object that defines the origin of x, see solarHourAngle.

Value

A Raster* object with pixel-wise solar incidence angles.

Note

An angle of more than 90 degrees, or likewise pi/2, indicates that the sun is behind the surface.

References

Duffie JA, Beckman WA (2013) Solar Engineering of Thermal Processes. Wiley: Hoboken, New Jersey, ISBN: 978-0-470-87366-3, http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470873663.html.

See Also

declination, solarHourAngle, terrain.

Examples

## import sample data
dem <- system.file("extdata/DEM.TIF", package = "satellite")
dem <- trim(projectRaster(raster(dem), crs = "+init=epsg:4326"))

## current solar incidence angle
solarIncidenceAngle(Sys.time(), dem, formula = "Spencer", 
                    unit = "degrees")

environmentalinformatics-marburg/satelliteTools documentation built on May 16, 2019, 8:16 a.m.