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Tham khảo tài liệu 'geoscience and remote sensing, new achievements part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 308 Geoscience and Remote Sensing New Achievements A.2 Discretization Next concerning the implementation and in order to describe the upward and downward diffuses radiance hemispherical distribution Verhoef 1998 proposes a discretization of hemispheres zenithal and azimuthal angles into N segments. In this case L- and L are replaced by sub-fluxes defined over the hemisphere segments forming together vectors called E- and E respectively. The operators of Eq. 72 are discretized accordingly in particular s s become vectors called s and s respectively A B becomes square matrices called A and B respectively and v and h become vectors called v and v respectively. Eqs. 72 73 74 75 76 become Verhoef 1998 i Es i k 0 0 0 0 i Es d d E- -s A -B 0 0 E- 1 E s B -A 0 0 E dz e o w v v -K 0 e o I Eo- I -w -v -v 0 K I Eo- 85 Note that as in the continuous case cf. Eq. 80 A could be written as A K - B . 86 with K and B the discrete scattering matrices corresponding to k and B respectively. The final solution linking the layer output fluxes to the input ones is Verhoef 1998 i Es L Tss 0 0 0 0 Es t E- L Tsd T R 0 0 E- t E t psd R T 0 0 E L E t pso pị Td Too 0 E t Eo- L Tso Tdo pTo 0 Too Eo- L 87 where L and t refer to the bottom and top of the layer respectively. Now let us consider the case when the source changes. This change includes both the direction and the way that the direct flux is scattered under the vegetation. Since the scattering properties depend only on the vegetation parameters and the source solid angle the latter possibility of change does not have a physical meaning. However it is needed in our case to define the scattering parameter when an effective vegetation density is considered. The variation has an impact over the scattering parameters of Eq. 85 as follows. The terms k s s and w change and the other matrix terms remain constant. The consequences over the boundary condition matrix concern elements that depend on the source and are Tss Tsd psd pso and Tso. Thus
