Isotropic Bihemispherical Reflectance (White Sky Albedo)
The isotropic bi-hemispherical reflectance is defined as the albedo of a target that is illuminated in a spatially-uniform manner at the top-of-canopy level by an isotropic diffuse light source, i.e., the intensity of the incident radiation is independent of direction. Based on these illumination conditions, the bhr_iso can then be said to be equal to:
where the projected solid angle [sr] is given in terms of zenith (θ) and azimuth (ϕ) angle by:
Notice that within RAMI all incident and exiting radiation has to pass through a (virtual) planar reference surface of specified lateral dimension and elevation above the target, and oriented perpendicular to the underlying surface normal.
|isotropic bihemispherical reflectance||%.6f|
|standard deviation of bhr_iso estimate*||%.6f|
*: if available, otherwise set to −1.000000.