European Commission - ROMC website

Within ROMC the Bi-directional Reflectance Factor (BRF) at a specific wavelength is defined as the radiant flux exiting from a target area in a particular direction - passing through a planar reference surface of specified lateral dimension and elevation above the target, and oriented perpendicular to the underlying surface normal - normalized by the equivalent quantity leaving from an infinitely large Lambertian background via the same reference surface and for the same directions of illumination and reflectance.

Measurement geometries along the principal observation plane for each illumination azimuth angle.

Measurement geometries along the orthogonal observation plane for each illumination azimuth angle.

The BRF measurement acquired e extend of that scene - unless specified otherwise in the experiment description page.

Formatting of measurement-file content

Header line content	# rows	# columns in file	Ratio of filtered rays ***
Header line format	integer	integer	real
Body lines content	SZA [rad]	VZA [rad]*	SAA - VAA [rad]*	BRF	Std. Dev. BRF **
Body lines format	real	real	real	real	real

*: if not defined (i.e. measurement #10: brf1) set to -1.000000.
**: if available, otherwise set to -1.000000.

where

SZA: Solar Zenith Angle (as indicated on the experimental description page)
SAA: Solar Azimuth Angle (as indicated on the xperimental description page)
VZA: Viewing Zenith Angle (as indicated on the experimental description page)
VAA: Viewing Azimuth Angle (0 radians for backward scattering in the principal plane, PI radians for forward scattering in the principal plane. For the orthogonal plane: PI/2 and 3PI/2 radians. Check the angular definitions section)
Ratio of filtered rays: The number of rays that perform the measurement divided by the total number of incident rays (for ray-tracingRT models only).
Std. Dev. BRF: Indication of the uncertainty in the BRF estimate as estimated from the radiative transfer model itself
A real is defined as having 6 digits after the decimal point, e.g., 1.000000.

Example of a correctly formatted file

17  5  1.000000
0.000000	0.3490658	3.141593	1.123456789	0.000286
0.000000	0.4363323	3.141593	0.265415465	0.000193
0.000000	0.4363323	4.712389	0.515161616	0.001069
0.000000	0.4363323	1.570796	0.251863158	0.000769
0.000000	0.5235988	3.141593	0.221654154	0.001226
0.000000	0.6981317	3.141593	0.136596353	0.000649
0.000000	0.7853981	3.141593	0.214415416	0.000434
0.000000	0.7853981	4.712389	0.524141354	0.000345
0.000000	0.7853981	1.570796	0.246346363	0.000375
0.000000	0.8726646	3.141593	0.264983962	0.001108
0.000000	1.047198	3.141593	0.248687463	0.001047
0.000000	1.047198	4.712389	0.624638462	0.000051
0.000000	1.047198	1.570796	0.246346343	0.000257
0.000000	1.221730	3.141593	0.246346545	0.000443
0.000000	1.308997	3.141593	0.324546333	0.000697
0.000000	1.308997	4.712389	0.354635456	0.000354
0.000000	1.308997	1.570796	0.234654453	0.000631

Prior to the performing of any RT model simulations, please refer to the Radiative transfer simulation definitions page located under the ROMC Info menu in the top navigation bar. Here you may find detailed instructions regarding the angular sign conventions for BRF simulations, as well as precise definitions of the required leaf normal distributions, the location and extend of the reference plane and other RT model technicalities. Also read the relevant file naming and formatting conventions that must be adhered to in order to avoid rejection of your results by the ROMC format checker.
Further information may also be found in the FAQs.

Measurement: gonio

Formatting of measurement-file content

Example of a correctly formatted file