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HET16,17,18/HET26,27,28

This set of experiments is proposed in order to simulate the radiative transfer regime in the RAMI-V spectral bands for heterogeneous leaf canopies composed of two structurally different layers with three (**overstories**) and two (**understories**) different densities, respectively. Each of these layers is represented by a large number of identical, non-overlapping spherical objects that are located over a horizontal background surface with uniform lambertian reflectance.

HETnn_DIS_d2d | Overstories density | Understories density |
---|---|---|

HET16_DIS_S2S | sparse | sparse |

HET17_DIS_M2S | medium | sparse |

HET18_DIS_D2S | dense | sparse |

HET26_DIS_S2D | sparse | dense |

HET27_DIS_M2D | medium | dense |

HET28_DIS_D2D | dense | dense |

The structural properties of these spherical objects are different between the upper (overstorey) and lower (understorey) layers. In the **understorey** layer, the spherical objects have a radius of 0.5 m and their centers are located 0.51 ± 0.0001 meters above the background plane (random height distribution). In the **overstorey** layer the spherical objects (crowns) have a radius of 5 m and center coordinates that vary between 7 and 11 meter above the background level (such that the maximum canopy height is 16m).

Each individual sphere contains a cloud of 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 to 5.0 $m^2/m^2$ for both the overstorey and understorey. 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 definition page). 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 is available for both understorey and overstorey spheres. This set of experiments is proposed in order to simulate the radiative transfer regime in the RAMI-V spectral bands for heterogeneous leaf canopies composed of two structurally different layers. Each of these layers is represented by a large number of identical, non-overlapping spherical objects that are located over and only partially covering a horizontal plane standing for the underlying background surface. The structural properties of these spherical objects are different between the upper (overstorey) and lower (understorey) layers. In the understorey layer, the spherical objects have a radius of 0.5m and their centers are located 0.51 ± 0.0001 meters above the background plane (random height distribution). In the overstorey layer the spherical objects have a radius of 5m and center coordinates that vary between 7 and 11 meter above the background level (such that the maximum canopy height is 16m). To address the needs of different RT models, both a statistical scene description, as well as ASCII files with the exact coordinates of the scatterers in the sphere (or the sphere locations in the scene) are provided.

These files contain 49999 lines with the values of R Xc Yc Zc Dx Dy Dz for each single leaf instance, to define a single crown.

Each crown should then be translated in space accordingly to the Table 2 and Table 3 below (Tree position property).

Overall, three different overstorey and two understorey densities are defined. As the spheres are identical copies of the two model defined above for understorey and overstorey, the overall canopy density is defined by the number of spheres (crowns) instantiated.

Understorey | Sparse | Dense |
---|---|---|

( X × Y × Z) [m × m × m] | 101.0 × 101.0 × ~1.01 | |

(Xmin, Ymin, Zmin) [m, m, m] | −50.5, −50.5, 0.0 | |

(Xmax, Ymax, Zmax) [m, m, m] | +50.5, +50.5, 15.90 | |

Scatterer shape | Disc of negligible thickness | |

Scatterer radius [m] | 0.005 | |

LAI of individual sphere | 5.0 | |

Scatterer normal distribution | Uniform | |

Foliage scattering law | Bi-Lambertian | |

Sphere radius [m] | 0.5 | |

Sphere center height range [m] | 0.5099 - 0.5101 | |

Background scattering law | Lambertian | |

Number of spheres | 2547 | 5093 |

LAI understorey ($m^2/m^2$) | 0.196 | 0.392 |

Tree position | link | link |

Overstories | Sparse | Medium | Dense |
---|---|---|---|

( X × Y × Z) [m × m × m]< | 101.0 × 101.0 × 15.90 | ||

(Xmin, Ymin, Zmin) [m, m, m] | −50.5, −50.5, 0.0 | ||

(Xmax, Ymax, Zmax) [m, m, m] | +50.5, +50.5, 15.90 | ||

Scatterer shape | Disc of negligible thickness | ||

Scatterer radius [m] | 0.05 | ||

LAI of individual sphere | 5.0 | ||

Scatterer normal distribution | Uniform | ||

Foliage scattering law | Bi-Lambertian | ||

Sphere radius [m] | 5.0 | ||

Number of spheres | see below for (overstorey) | ||

Sphere center height range [m] | 7.0 - 11.0 | ||

Background scattering law | Lambertian | ||

Number of trees | 18 | 37 | 59 |

LAI overstorey ($m^2/m^2$) | 0.69 | 1.42 | 2.27 |

Tree position | link | link | link |

Within a given sphere the Bi-Lambertian foliage elements of the **overstorey** layer are characterized by specified radiative properties (reflectance, transmittance) defined by **STDL_REFL** and **STDL_TRAN** spectral values given in file for each RAMI-V spectral bands. The corresponding optical properties of the **understorey** layer are defined by the values labelled as **LEAF2_REFL** and **LEAF2_TRAN**.

The soil background is characterized by a lambertian reflectance defined by the **SOIL2** values given in the optical properties file.

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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_**).