solarIncidenceAngle: Compute solar incidence angle

Description Usage Arguments Value Note References See Also Examples

Description

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

Usage

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## 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

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## 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 March 24, 2018, 4:08 a.m.