5.5 Algorithms

The retrieval of FVC, LAI and fAPAR in the LSA SAF rely on Spectral Mixture Analysis (SMA); the signal from a single pixel (surface reflectance) is assumed to be the contribution of different vegetation and bare soil components within the scene (next figure).

SMA_figure

As detailed in Chapter 2, the surface BRDF may be written as:

ρ (θs, θv, φ) = K0 + K1 x F1s, θv, φ) + K2 x F2s, θv, φ)

Where:

    K0 - represents isotropic reflectance;
    K1 - represents geometric reflectance;
    K2 - represents volumetric reflectance;

Parameters K0 in the SEVIRI channels VIS 0.6 μm, VIS 0.8 μm and NIR 1.6 μm are used to determine FVC and LAI, while fAPAR uses K0, K1 and K2.