Total transmission at lower boundary level for direct illumination only
This is the fraction of the incident direct radiation - passing through a (virtual) reference surface of specified lateral dimension and elevation above the target, and oriented perpendicular to the underlying surface normal - that passes in downward direction through a second identical (virtual) reference plane located at the level of the background surface at z = ~ 0. ftran_tot_dir includes uncollided radiation, radiation collided with the canopy only, and also contributions due to radiation that is reflected back up from background before being scattered down to the background again by the canopy. ftran_tot_dir does not include contributions from isotropic-diffuse illumination sources (should they be prescribed in the illumination conditions of a given RAMI experiment).
ftran_tot_dir = ftran_uc_dir + ftran_coco_dir + contribution from radiation bouncing back and forth between canopy and background.
|standard deviation of bhr_iso estimate*||%.6f|
*: if available, otherwise set to −1.000000.