satellite (version 1.0.5)

calcTOAIrradModel: Compute top of atmosphere solar irradiance for sensor bands using LUTs

Description

Compute mean extraterrestrial solar irradiance (ESun) using tabulated mean solar spectral data and the band specific relative spectral response (rsr) functions.

Usage

# S4 method for Satellite
calcTOAIrradModel(x, model = "MNewKur", normalize = TRUE, esd)
# S4 method for data.frame
calcTOAIrradModel(x, model = "MNewKur", normalize = TRUE, esd)

Value

If x is a Satellite object, a Satellite object with ESun information added to the metadata; if x is a data.frame, a vector containing ESun for the respective band(s).

Arguments

x

A Satellite object or the relative spectral response function for the respective band as data.frame (see details for structure).

model

Tabulated solar radiation model to be used (one of MCebKur_MChKur, MNewKur, MthKur, MoldKur, MODWherli_WMO, NN, see reference on tabulated solar irradiance below).

normalize

Logical; if TRUE, ESun is normalized to mean earth-sun distance.

esd

Earth-sun distance (AU, can be estimated using calcEarthSunDist). If x is a Satellite object and esd is not supplied and necessary for normalization, it is tried to take it from the metadata, otherwise it is estimated by the day of the year using calcEarthSunDist.

Details

Computation of ESun is taken from Updike and Comp (2011).

Tabulated values for mean earth-sun distance are taken from the data sources mentioned in the references.

If results should not be normalized to a mean earth-sun distance, the actual earth-sun distance is approximated by the day of the year using calcEarthSunDist.

Relative spectral response values have to be supplied as a data.frame which has at least the following three columns: (i) a column "Band" for the sensor band number (i.e. 1, 2, etc.), (ii) a column "WAVELENGTH" for the WAVELENGTH data in full nm steps, and (iii) a column "RSR" for the response information [0...1].

References

Updike T, Comp C (2011) Radiometric use of WorldView-2 imagery. Technical Note, available online at http://www.pancroma.com/downloads/Radiometric_Use_of_WorldView-2_Imagery.pdf.

Tabulated relative spectral response functions (nm-1) are taken from the spectral viewer of the USGS Landsat FAQ.

Tabulated solar irradiance (W m-2 nm-1) is taken from the National Renewable Energy Laboratory.

See Also

calcTOAIrradTable for tabulated solar irradiance values from the literature or calcTOAIrradRadRef for the computation of the solar irradiance based on maximum radiation and reflection values of the dataset.

See calcEarthSunDist for calculating the earth-sun distance based on the day of the year which is called by this function if ESun should be corrected for actual earth-sun distance.

Examples

path <- system.file("extdata", package = "satellite")
files <- list.files(path, pattern = glob2rx("LC08*.TIF"), full.names = TRUE)
sat <- satellite(files)
sat <- calcTOAIrradModel(sat)
getSatESUN(sat)

lut <- lutInfo()
calcTOAIrradModel(lut$L8_RSR, model = "MNewKur", normalize = FALSE, 
  esd = calcEarthSunDist("2015-01-01"))