Sample sun luminance at the disk center. — calculate_sun

Evaluate the Prague or Hosek sky model at the sun center and integrate against the CIE Y curve to return a luminance value. This is useful for relative attenuation (e.g., comparing zenith sun to a low sun).

Usage

calculate_sun_brightness(
  elevation = 10,
  azimuth = 90,
  albedo = 0.5,
  turbidity = 3,
  altitude = 0,
  visibility = 50,
  hosek = TRUE,
  wide_spectrum = FALSE,
  lambda_nm = NULL
)

Arguments

elevation: Default 10. Solar elevation angle above/below the horizon (degrees). Range [-4.2, 90] for Prague, [0, 90] for Hosek.
azimuth: Default 90. Solar azimuth (degrees).
albedo: Default 0.5. Ground albedo, range 0 to 1.
turbidity: Default 3. Atmospheric turbidity, range 1.7 to 10 (Hosek only).
altitude: Default 0. Observer altitude (m), range 0 to 15000 (Prague only).
visibility: Default 50. Meteorological range (km); Prague only.
hosek: Default TRUE. FALSE selects the Prague model.
wide_spectrum: Default FALSE. Use wide-spectrum (55-channel) coefficients for Prague at sea level only.
lambda_nm: Optional vector of wavelengths for Hosek sampling.

Value

Numeric scalar of sun luminance (CIE Y, relative scale).

Examples

if(run_documentation()) {
  calculate_sun_brightness(elevation = 45, hosek = TRUE)
}
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