Isotropic Bihemispherical Reflectance (White Sky Albedo): bhr_iso
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.
Within RAMI-IV this measurement applies only to a selection of canopy scenes:
- ACTUAL CANOPIES : JARVSELJA SUMMER PINESTAND
- ACTUAL CANOPIES : OFENPASS WINTER PINESTAND
- ACTUAL CANOPIES : JARVSELJA SUMMER BIRCHSTAND
- ACTUAL CANOPIES : JARVSELJA WINTER BIRCHSTAND
Formatting of measurement-file content:
|Content||isotropic bihemispherical reflectance||standard deviation of bhr_iso estimate*|
A real is defined as having 6 digits after the decimal point, e.g., 1.000000.