Directional Hemispherical Reflectance (Black Sky Albedo)
The directional hemispherical reflectance (DHR) is defined as the albedo of a
target under direct illumination only.
Known also as black-sky albedo is, along with the white-sky albedo
(or bi-hemispherical reflectance, BHR), a typical
remote sensing product. It is related to th bidirectional reflectance factor (BRF)
through the equation
$$DHR(\theta_i,\phi_i;2\pi)=\frac{1}{\pi} \int BRF(\theta_i,\phi_i;\theta_r,\theta_r) d\Omega_r$$
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.
Simulations can be performed for all RAMI-V bands excluding GED. Sun geometries are the same as
defined for brfpp and brfop measurements types, hence they depends on the specific scene (link or table again).
| Content | Format |
|---|---|
| directional hemispherical reflectance | %.6f |
| standard deviation of dhr estimate* | %.6f |
*: if available, otherwise set to −1.000000.
0.123456 -1.000000