get.brdf

get.brdf simulates the bidirectional reflectance (and, optionally, the directional thermal, fluorescence and xanthophyll-related radiance) of the canopy over a large set of viewing angles, by repeatedly calling getRTMo (and, depending on data.opts, get.RTMt.planck, get.RTMf, get.RTMz) for each requested angle combination. The viewing angles requested in data.directional are extended with a set of angles for hot-spot oversampling and principal-plane oversampling, and duplicate angle combinations are removed before the loop.

Usage

get.brdf(
  data.spectral,
  data.angles,
  data.rad,
  data.directional,
  atmo,
  data.soil,
  data.leafopt,
  data.leafbio,
  data.canopy,
  data.gap,
  data.meteo,
  data.thermal,
  data.bcu,
  data.bch,
  data.opts,
  get.plots = F
)

Arguments

data.spectral

list. Spectral band definitions used throughout the model (e.g. wlS, wlF, wlT).

data.angles

list. Base observation geometry, with element tts (solar zenith angle, degrees) used to construct the hot-spot oversampling angles.

data.rad

list. Radiation fluxes and top-of-canopy irradiance computed previously by getRTMo, passed through to the thermal/fluorescence/xanthophyll sub-models.

data.directional

list. User-requested directional observation geometry, with elements psi (relative azimuth angles, degrees) and tto (viewing zenith angles, degrees).

atmo

list or data.frame. Atmospheric input (MODTRAN transmittance functions or precomputed Esun_/Esky_), passed to getRTMo.

data.soil

list. Soil reflectance and related soil properties.

data.leafopt

list. Leaf optical properties (reflectance/transmittance spectra) computed by the leaf optical model.

data.leafbio

list. Leaf biochemical/biophysical parameters (Cab, Cw, Cdm, N, ...).

data.canopy

list. Canopy structural properties (LAI, leaf inclination distribution, hot-spot parameter, etc.).

data.gap

list. Gap fraction probabilities (Ps, Po, Pso) needed to combine sunlit/shaded contributions in the thermal, fluorescence and xanthophyll sub-models.

data.meteo

list. Meteorological forcing data (e.g. air temperature, vapour pressure).

data.thermal

list. Component temperatures from the energy balance: Tcu (sunlit canopy), Tch (shaded canopy), Tsu (sunlit soil), Tsh (shaded soil), all in deg C.

data.bcu

list. Biochemical outputs for sunlit leaves, including eta (relative fluorescence emission efficiency) and Kn (non-photochemical quenching rate constant).

data.bch

list. Biochemical outputs for shaded leaves, with the same structure as data.bcu.

data.opts

data.frame. Model configuration options; rows used here are calc_planck (compute thermal radiance spectrum), calc_fluor (compute chlorophyll fluorescence), and calc_xanthophyllabs (include xanthophyll de-epoxidation effect on reflectance).

get.plots

logical. If TRUE, diagnostic plots are produced by the underlying RTM calls. Default FALSE.

Value

A list directional with matrices indexed by wavelength (rows) and viewing angle (columns), including:

psi, tto

numeric vectors. The (deduplicated) relative azimuth and viewing zenith angles actually simulated.

refl_

TOC reflectance spectrum per angle.

rso_

Directional-directional BRDF per angle.

Lo_

TOC outgoing radiance per angle.

LoF_

TOC fluorescence radiance per angle (if calc_fluor is enabled).

Lot_

TOC thermal radiance per angle (if calc_planck is enabled).

Eoutte, BrightnessT

Placeholder outputs (currently left at their initialized zero values).

Author

Carlos Camino

Examples

if (FALSE) { # \dontrun{
directional <- get.brdf(data.spectral, data.angles, data.rad, data.directional, atmo,
                         data.soil, data.leafopt, data.leafbio, data.canopy, data.gap,
                         data.meteo, data.thermal, data.bcu, data.bch, data.opts)
} # }