Surface Reflectance - Process to L2A

Water Network

For each L1C data file (one per relative azimuth angle), the surface reflectances and water radiances (computed at each \(L_u\) timestamp) are averaged, respectively. This results in L2A files containing one spectrum for each variable (i.e., water-leaving radiance, and, water reflectance with and without the NIR similarity correction) and the associated uncertainties.

Land Network

For the land network, the surface reflectances can now be calculated from the L1C radiances (\(L_u\)) and irradiances (\(E_d\)) as:

\[\rho =\pi\frac{L_u}{E_d}\]

We note that this surface reflectance is technically the hemispherical-conical reflectance factor and not the bidirectional reflectance factor, as the contribution from sky reflectance is included in the measurements and the field-of-view of the LANDHYPERNET instruments is 5°.