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17-May-2022   
Path: RAMI-IV : EXPERIMENTS : ABSTRACT CANOPIES : HETEROGENEOUS : ANISOTROPIC BACKGROUND
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Heterogeneous canopies with anisotropic background:HET10, HET11, HET12 and HET20, HET21, HET22

This set of experiments is suggested to simulate the radiative transfer regime in the red and near infra-red spectral bands for heterogeneous leaf canopies composed of a large number of identical, non-overlapping spherical objects - representing the individual plant crowns - located over and only partially covering a NON-LAMBERTIAN horizontal plane standing for the underlying background surface. These 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) 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 (i.e., number of spheres per scene) are proposed: medium=0.2 and dense=0.4 coverages. 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 5.0 [m² ⁄ m²]. Within a given sphere the Bi-Lambertian foliage elements are characterized by specified radiative properties (reflectance, transmittance) defined separately for both the visible and near-infrared spectral domains. The orientation of the normals of the foliage elements (scatterers) follows a uniform (or what is sometimes called a 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). The BRF of the anisotropically scattering background (which is intended to represent snow, bare soil and understorey vegetation conditions, respectively) is expressed with the parametric RPV model. Participants who wish to fit their own anisotropic background model to the RPV-simulated BRF data should inform the RAMI coordinators of this via the report files.

The following figures exhibit graphical representations of the sparse and dense scenes:

The tables below provide the details required to build and run a RT model on the sparse scene with anisotropic scattering properties of the underlying background (snow, vegetation, soil).

Scene properties:

( 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
Number of spheres 2547
Fractional scene area coverage of spheres 0.1961
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)

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 ~ 2.7 Mbytes and) contains 49999 lines of format R Xc Yc Zc Dx Dy Dz that 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 for the medium dense scene can be found here.

The tables below provide detailed information regarding the illumination conditions and spectral properties of the foliage and background constituents of the sparse canopy scenarios. 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). Two spectral bands (red and NIR) and two illumination conditions (direct only with SZA=20° and 50°) are proposed for three different background anisotropy scenarios, referred to as HET10, HET11 and HET12 in the tables below. The difference between experiments HET10, HET11 and HET12 thus lies only in the BRF of the anisotropically scattering background (assumed to be reminiscent of snow, bare soil, and understorey vegetation). The background BRF is described by the three parameter of the RPV model.

Experiment identifier tag <EXP> : HET10_DIS_UNI_RED_20 HET11_DIS_UNI_RED_20 HET12_DIS_UNI_RED_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.06 0.06 0.06
Leaf scatterer transmittance 0.02 0.02 0.02
background BRF pattern
(RPV model parameters)
ρ0=0.075
k=0.55
Θ=−0.25
RPV simulated BRF data
ρ0=0.750
k=0.95
Θ=0.15
RPV simulated BRF data
ρ0=0.050
k=0.95
Θ=−0.10
RPV simulated BRF data

Experiment identifier tag <EXP> : HET10_DIS_UNI_NIR_20 HET11_DIS_UNI_NIR_20 HET12_DIS_UNI_NIR_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.50 0.50 0.50
Leaf scatterer transmittance 0.44 0.44 0.44
background BRF pattern
(RPV model parameters)
ρ0=0.10
k=0.60
Θ=−0.20
RPV simulated BRF data
ρ0=0.70
k=0.95
Θ=0.10
RPV simulated BRF data
ρ0=0.15
k=0.80
Θ=−0.05
RPV simulated BRF data

Experiment identifier tag <EXP> : HET10_DIS_UNI_RED_50 HET11_DIS_UNI_RED_50 HET12_DIS_UNI_RED_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.06 0.06 0.06
Leaf scatterer transmittance 0.02 0.02 0.02
background BRF pattern
(RPV model parameters)
ρ0=0.075
k=0.55
Θ=−0.25
RPV simulated BRF data
ρ0=0.750
k=0.95
Θ=0.15
RPV simulated BRF data
ρ0=0.050
k=0.95
Θ=−0.10
RPV simulated BRF data

Experiment identifier tag <EXP> : HET10_DIS_UNI_NIR_50 HET11_DIS_UNI_NIR_50 HET12_DIS_UNI_NIR_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.50 0.50 0.50
Leaf scatterer transmittance 0.44 0.44 0.44
background BRF pattern
(RPV model parameters)
ρ0=0.10
k=0.60
Θ=−0.20
RPV simulated BRF data
ρ0=0.70
k=0.95
Θ=0.10
RPV simulated BRF data
ρ0=0.15
k=0.80
Θ=−0.05
RPV simulated BRF data

The tables below provide the details required to build and run a RT model on the dense scene with anisotropic scattering properties of the underlying background (snow, vegetation, soil).

Scene properties:

( 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
Number of spheres 5093
Fractional scene area coverage of spheres 0.3921
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)

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 ~ 2.7 Mbytes and) contains 49999 lines of format R Xc Yc Zc Dx Dy Dz that 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 for the medium dense scene can be found here.

The tables below provide detailed information regarding the illumination conditions and spectral properties of the foliage and background constituents of the sparse canopy scenarios. 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). Two spectral bands (red and NIR) and two illumination conditions (direct only with SZA=20° and 50°) are proposed for three different background anisotropy scenarios, referred to as HET20, HET21 and HET22 in the tables below. The difference between experiments HET20, HET21 and HET22 thus lies only in the BRF of the anisotropically scattering background (assumed to be reminiscent of snow, bare soil, and understorey vegetation). The background BRF is described by the three parameter of the RPV model.

Experiment identifier tag <EXP> : HET20_DIS_UNI_RED_20 HET21_DIS_UNI_RED_20 HET22_DIS_UNI_RED_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.06 0.06 0.06
Leaf scatterer transmittance 0.02 0.02 0.02
background BRF pattern
(RPV model parameters)
ρ0=0.075
k=0.55
Θ=−0.25
RPV simulated BRF data
ρ0=0.750
k=0.95
Θ=0.15
RPV simulated BRF data
ρ0=0.050
k=0.95
Θ=−0.10
RPV simulated BRF data

Experiment identifier tag <EXP> : HET20_DIS_UNI_NIR_20 HET21_DIS_UNI_NIR_20 HET22_DIS_UNI_NIR_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.50 0.50 0.50
Leaf scatterer transmittance 0.44 0.44 0.44
background BRF pattern
(RPV model parameters)
ρ0=0.10
k=0.60
Θ=−0.20
RPV simulated BRF data
ρ0=0.70
k=0.95
Θ=0.10
RPV simulated BRF data
ρ0=0.15
k=0.80
Θ=−0.05
RPV simulated BRF data

Experiment identifier tag <EXP> : HET20_DIS_UNI_RED_50 HET21_DIS_UNI_RED_50 HET22_DIS_UNI_RED_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.06 0.06 0.06
Leaf scatterer transmittance 0.02 0.02 0.02
background BRF pattern
(RPV model parameters)
ρ0=0.075
k=0.55
Θ=−0.25
RPV simulated BRF data
ρ0=0.750
k=0.95
Θ=0.15
RPV simulated BRF data
ρ0=0.050
k=0.95
Θ=−0.10
RPV simulated BRF data

Experiment identifier tag <EXP> : HET20_DIS_UNI_NIR_50 HET21_DIS_UNI_NIR_50 HET22_DIS_UNI_NIR_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Leaf scatterer reflectance 0.50 0.50 0.50
Leaf scatterer transmittance 0.44 0.44 0.44
background BRF pattern
(RPV model parameters)
ρ0=0.10
k=0.60
Θ=−0.20
RPV simulated BRF data
ρ0=0.70
k=0.95
Θ=0.10
RPV simulated BRF data
ρ0=0.15
k=0.80
Θ=−0.05
RPV simulated BRF data


Below is a list of the various measurements that are required for these test cases:


Prior to the performing of any RT model simulations, please refer to the 'definitions' pages for detailed instructions regarding the angular sign conventions for BRF simulations, as well as other RT model technicalities. Also read the relevant file naming and formatting conventions that must be adhered to by all participants. In addition, RAMI-IV offers participants the possibility to test the compliance of their model-generated results files with these file-naming and formatting convention, prior to their submission via ftp: To do so follow the on-line format checker link that appears in the top navigation bar during the active submission period.

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