HET10,11,12/HET20,21,22
This set of scenes are provided to simulate the radiative transfer regimes in the RAMI-V spectral bands for two heterogeneous canopies composed of a large number of identical and non-overlapping spherical objects (plant crowns) distributed over a horizontal background surface with different non-lambertian reflectance properties. Six flavors of the scene originates from the combination of two by three different surface parameterizations as listed in Table 1.
| HETnn_DIS_d1r | Overstorey | Surface properties (BRF model) |
|---|---|---|
| HET10_DIS_S1A | sparse | A (soil, RPV4_) |
| HET11_DIS_S1B | sparse | B (snow, RPV8_) |
| HET12_DIS_S1C | sparse | C (understorey vegetation, RPVS_) |
| HET20_DIS_D1A | dense | A |
| HET21_DIS_D1B | dense | B |
| HET22_DIS_D1C | dense | C |
These spherical objects have a radius of 0.5m and their centres are located 0.51 ± 0.0001 meters above the background plane (random height distribution) to yield a maximum canopy height of ~1.01m. To address the needs of different RT models, both a statistical scene description, as well as a file with the exact coordinates of every single scatterer in the canopy are provided.
Two different fractional coverages are proposed: sparse with fractional coverage of 0.2 and dense (0.4). Each individual sphere contains a 'cloud' of oriented finite-sized particles representing the foliage.
The leaf area index (LAI) of a single sphere (LAI = area of leaves/maximum cross section of sphere) is fixed and amounts to 5.0m2/m2.
The orientation of the normals of the foliage elements (scatterers) follows a uniform (or spherical) distribution function, i.e., the probability to be intercepted by a leaf is independent of the direction of travel of the radiation (see the definitions page).
Tables 2 provides the details of the vegetation part for sparse (HET10,11,12) and dense (HET 20,21,22) scenes. The optical properties of the leaf (standard green leaf, STDL) and of the underlying surfaces (flavor: A, B, C) are given in the Spectral characteristics section.
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, meant to build an individual crown contains 49999 leaf instances. Its header is R Xc Yc Zc Dx Dy Dz.
Each tree should then be translated in space accordingly to the two different files for sparse and dense scene flavors given in Table 2 (Tree positions).
| Properties | Sparse | Dense |
|---|---|---|
| ( X × Y × Z) | 101.0 × 101.0 × 1.01 [m × m × m] | |
| (Xmin, Ymin, Zmin) | −50.5, −50.5, 0.0 [m, m, m] | |
| (Xmax, Ymax, Zmax) | +50.5, +50.5, 1.0101 [m, m, m] | |
| Scatterer shape | Disc of negligible thickness | |
| Scatterer radius | 0.005 [m] | |
| LAI of individual sphere | 5.0 | |
| Scatterer normal distribution | Uniform | |
| Foliage scattering law | Bi-Lambertian | |
| Sphere radius | 0.5 [m] | |
| Minimum sphere center height | 0.5099 [m] | |
| Maximum sphere center height | 0.5101 [m] | |
| Background BRF pattern | Non-Lambertian (see tables below) | |
| Number of spheres | 2547 | 5093 |
| Fractional scene area coverage of spheres | 0.1961 | 0.3921 |
| Tree position | link | link |
Within a given sphere the Bi-Lambertian foliage elements are characterized by specified radiative properties (reflectance, transmittance) defined by STDL_REFL and STDL_TRAN spectral values given here for each RAMI-V spectral band.
The BRF of the anisotropic scattering background (which is intended to represent bare soil, snow, and understorey vegetation conditions) is expressed in terms of $\rho_0$,k and $\Theta$ parameters of the RPV model. The parameters labeled with RPV4_ should be used for HET10, HET20 (soil background), RPV8_ for HET11, HET21 (snow background) and RPVS_ for HET12, HET22 (understorey vegetation) scenes, can be found here.
loading...
loading...
The illumination conditions are very likely dependent on the kind of measurement in RAMI-V more than in previous RAMI phases. For brf*, dhr, fabs*, ftran* measurements, except brf_sat, the illumination were listed in the description of measure brfpp, and duplicated in other measure description pages. For these geometries the tag will be _zZZaAAA_ with ZZ and AAA defining $\theta_i$ and $\phi_i$, respectively. In addition, diffuse isotropic illumination is foreseen for bhr, fabs*, ftran* measures (geometry tag will then be _DIFFUSE_).
