This set of experiments was suggested to simulate the radiative transfer regime in the red and near infra-red spectral bands for heterogeneous environmental scenes composed of a large number of non overlapping spherical objects representing the individual plant crowns, located over and only partially covering a horizontal plane standing for the underlying soil surface.
These objects, in turn, contained randomly distributed finite size disc-shaped scatterers characterized by the specified radiative properties (reflectance, transmittance), and the orientation of the normals to the scatterers followed exclusively a uniform distribution function. The radiative properties of the underlying soil were also specified (in this case a simple Lambertian scattering law). The particular values selected for these input variables represented classical plant canopy conditions.
The following figures exhibit a graphical representation of such a scene,
from the side
and from the top:
The zero azimuth line is defined along the northern direction and coincides with the positive x axis as indicated in the diagram below:
The architecture of this scene (HET01) is precisely characterized as follows:
|( X × Y × Z)||100.0 × 100.0 × 30.0 [m × m × m]|
|(Xmin, Ymin, Zmin)||−50.0, −50.0, 0.0 [m, m, m]|
|(Xmin, Ymax, Zmin)||−50.0, +50.0, 0.0 [m, m, m]|
|(Xmax, Ymin, Zmin)||+50.0, −50.0, 0.0 [m, m, m]|
|(Xmax, Ymax, Zmin)||+50.0, +50.0, 0.0 [m, m, m]|
|(Xmin, Ymin, Zmax)||−50.0, −50.0, 30.0 [m, m, m]|
|(Xmin, Ymax, Zmax)||−50.0, +50.0, 30.0 [m, m, m]|
|(Xmax, Ymin, Zmax)||+50.0, −50.0, 30.0 [m, m, m]|
|(Xmax, Ymax, Zmax)||+50.0, +50.0, 30.0 [m, m, m]|
|Scatterer shape||Disc of negligible thickness|
|Scatterer radius||0.1 [m]|
|LAI of individual sphere||5.0|
|Scatterer normal distribution||Uniform|
|Number of spheres||15|
|Fractional scene area coverage of spheres||0.471|
|Sphere radius||10.0 [m]|
|Minimum sphere center height||11.0 [m]|
|Maximum sphere center height||19.0 [m]|
where the Leaf Area Index (LAI) is calculated as follows:
LAI = (# of leaves × one-sided area of single leaf) ⁄ (π × square of the radius of sphere)
The coordinates (X, Y, Z) of the sphere centers are as follows:
|−24.8302; 11.6110; 15.6210||−38.3380; −9.06342; 17.6094||−31.3562; 32.5297; 14.3051|
|11.9126; 8.32062; 12.1220||39.4855; 37.1247; 16.3647||−8.30999; −4.39422; 14.4241|
|12.2769; −25.1402; 12.4492||32.4756; −26.9023; 16.3684||−7.46991; −32.2138; 12.6678|
|−27.4794; −32.0266; 15.9146||33.5709; −6.31039; 14.5332||−5.24326; 39.8405; 16.8247|
|18.1699; 35.8223; 11.5683||−5.26569; 18.9618; 17.2535||37.8226; 14.6769; 11.5936|
The underlying soil is occupying the entire lower surface of the scene, i.e., the area enclosed between the following coordinates: (−50.0, −50.0, 0.0), (−50.0, +50.0, 0.0), (+50.0, −50.0, 0.0), and (+50.0, +50.0, 0.0), where all values are in meters.
The tables below provide the details required to execute each of the experiments in this category. Every table is preceeded by the corresponding experiment identifier tag <EXP> that is needed in the naming of the various measurement results files (see file naming and formatting conventions).
The various testcases that are defined within this phase of the RAMI initiative can be visualized on their respective description pages:
The following Figure shows the detailed contributions of the individual models to a series of histograms of local angular model deviation values estimated for viewing conditions in the principal plane and cross planes, in both the red and near-infrared wavelengths, for the ensemble of the discrete representations of the "Floating Spheres" heterogeneous test cases. Clockwise from the top left panel are shown: the total, the multiple scattered, the single-scattered by vegetation, and the single-scattered by soil BRF components.