Isotropic Bihemispherical Reflectance (White Sky Albedo)
The bi-hemispherical reflectance is defined as the albedo of a target under isotropic diffuse illumination (i.e., the intensity of the incident radiation is independent on direction). It is also known as white-sky albedo, and can be calculated as $$BHR(2\pi,2\pi)=\int \int BRF(\theta_i,\phi_i,\theta_r,\theta_r)d\Omega_i d\Omega_r$$ where the projected solid angle [sr] is given in terms of zenith ($\theta$) and azimuth ($\phi$) angles by $d\Omega = \sin\theta \cos\theta d\theta d\phi$. 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.
*: if available, otherwise set to −1.000000.
0.123456 -1.000000
