NIR_obs = observed reflectance factors; NIR_mod = modelled reflectance; NIR_norm = normalised reflectance; SZA = solar zenith angle; RAA = relative azimuth angle. The model parameters retrieved are shown below the chart title. "Negative" view zenith angles indicate backscattering.
This NIR channel distribution is for a Stipa grandis grassland at
the peak of the growing season (late August). The sensor - a 4-channel Milton
radiometer - was 4 metres above the surface when viewing at nadir and was
tilted from 40 degrees in the backscattering direction to 40 degrees in the
forward-scattering direction, close to the principal plane (the plane made by
the target, the sensor and the sun) as shown here. A photograph of the radiometer and mast is
shown
here in the Stipa gobica desert steppe zone.
The chart also shows values modelled by the Roujean model and the same data
normalised by a BRDF adjustment based on the model.