Discrete

RAMI3 phase


This set of experiments is the same as for RAMI phase 1 and 2 and requires to simulate the radiative transfer regime in the red and near infra-red spectral bands for heterogeneous environments.

These scenes - which are structurally identical to those used for the discrete floating spheres test cases in the purist corner - are 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. To address the needs of different RT models, we are providing both a statistical scene description, as well as, a file with the exact coordinates of every leaf in one of the spherical volumes. You may or may not make use of this information depending on the needs of your particular model.

Side scene representation
The figure exhibits a graphical representation of such a scene, from the side.
Top scene representation
The figure exhibits a graphical representation of such a scene, from the top.
The zero azimuth line
The zero azimuth line.

The architecture of this scene (HET01) is precisely characterized as follows:

Scene dimensions:

( 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 shapeDisc of negligible thickness
Scatterer radius0.1 [m]
LAI of individual sphere5.0
Scatterer normal distributionUniform
Number of spheres15
Fractional scene area coverage of spheres0.471
Sphere radius10.0 [m]
Minimum sphere center height11.0 [m]
Maximum sphere center height19.0 [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)

An ASCII file with the radius (R), centre coordinates (Xc,Yc,Zc), and direction cosines (Dx,Dy,Dz) of every single leaf in a spherical volumes centered at 0,0,0 can be found here. This file (is ~ 2.2 Mbytes and) contains 49999 lines of format R Xc Yc Zc Dx Dy Dz and may serve as input to your scene creation process (provided that you are able to create multiple instances of its content, each one of which is then translated to the actual locations of the sphere centers in the scene. The coordinates (X, Y, Z) of the various 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; 12.122039.4855; 37.1247; 16.3647−8.30999; −4.39422; 14.4241
12.2769; −25.1402; 12.449232.4756; −26.9023; 16.3684−7.46991; −32.2138; 12.6678
−27.4794; −32.0266; 15.914633.5709; −6.31039; 14.5332−5.24326; 39.8405; 16.8247
18.1699; 35.8223; 11.5683−5.26569; 18.9618; 17.253537.8226; 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 that is needed in the naming of the various measurement results files (see file naming and formatting conventions).

brf1

Results for Spectral albedo (Directional Hemispherical Reflectance)

brfop

Results for BRF in the cross plane (perpendicular to the principal plane)

brfop_co_sgl

Results for BRF in the cross plane for single-scattered radiation

brfop_mlt

Results for BRF in the cross plane for multiple-scattered (two or more scattering events) radiation

brfop_uc_sgl

Results for BRF in the cross plane for single-scattered radiation collided by the soil

brfpp

Results for BRF in the principal plane (total)

brfpp_co_sgl

Results for BRF in the principal plane for single-scattered radiation

brfpp_mlt

Results for BRF in the principal plane for multiple-scattered (two or more scattering events) radiation

brfpp_uc_sgl

Results for BRF in the principal plane for single-scattered radiation collided by the soil

fabs

Results for Absorption by the canopy (turbid or discrete)

ftran

Results for Total transmission through the medium at the lower boundary level