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17-May-2022   
Path: RAMI-IV : EXPERIMENTS : ABSTRACT CANOPIES : HOMOGENEOUS : TWO CANOPY LAYERS
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Homogeneous discrete cases with two canopy layers: HOM26, HOM27, HOM28 and HOM36, HOM37, HOM38

This set of experiments is suggested to simulate the radiative transfer regime in the red and near infra-red spectral bands for spatially homogeneous leaf canopies composed of two different horizontal layers (reminiscent of the overstorey and understorey of plant canopies). Each layer contains a large number of non overlapping disc-shaped objects representing the foliage elements. The structural and spectral properties of the scatterers are different from one layer to the other. The underlying background is Lambertian. 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 is provided.

The foliage objects are randomly distributed finite size disc-shaped scatterers characterized by the specified radiative properties (reflectance, transmittance) for each layer, and the orientation of the normals to the scatterers which follow erectophile and planophile distribution functions. The particular values selected for the various input variables represent typical plant canopy conditions.

The following figure exhibits a graphical representation of such a scene:

The tables below provide the details required to implement and perform each of the experiments in this category. Every table is preceded 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 first set of two-layer plane-parallel discrete experiments refers to a vegetation canopy with a top layer having a thickness of 1m, an erectophile leaf normal distribution, a scatterer radius of 0.05 m, and a Leaf Area Index of 1 m² ⁄ m². The bottom layer features a planophile leaf normal distribution, identical scatterer radius (0.05m) and height (1m) as the top layer, and three different LAI values (1, 2 and 5 m² ⁄ m²). The overall canopy height is 2m. The scattering laws of (both sides of the) foliage elements and the background surface are Lambertian. Two spectral bands (red and NIR) and two illumination conditions (direct only with SZA=20° and 50°) are proposed for each one of the above three structural scenarios, referred to as HOM26, HOM27 and HOM28 in the tables below.

For 3D RT models capable of using the deterministic position and orientation of all scatterers in the scenes three ASCII files are provided that contain the layer ID (TLL=top layer leaf and BLL=bottom layer leaf), the leaf/disc radius (R), the leaf/disc centre coordinates (Xc,Yc,Zc), and the direction cosines (Dx,Dy,Dz) of every single leaf/disc in a 25×25 m² canopy section. The size of these ASCII files is several Mbytes and the format of its content is L_id R Xc Yc Zc Dx Dy Dz. The deterministic foliage location and orientation information can be found via the next three links: HOM26 (20.7 Mbytes), HOM27 (10.4 Mbytes), and HOM28 (6.9 Mbytes).

Experiment identifier tag <EXP> : HOM26_DIS_EAP_RED_20 HOM27_DIS_EAP_RED_20 HOM28_DIS_EAP_RED_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Top Layer Leaf scatterer reflectance 0.04 0.04 0.04
Top Layer Leaf scatterer transmittance 0.04 0.04 0.04
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Planophile Planophile Planophile
Bottom Layer Leaf scatterer reflectance 0.06 0.06 0.06
Bottom Layer Leaf scatterer transmittance 0.02 0.02 0.02
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.13 0.13 0.13

Experiment identifier tag <EXP> : HOM26_DIS_EAP_NIR_20 HOM27_DIS_EAP_NIR_20 HOM28_DIS_EAP_NIR_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Top Layer Leaf scatterer reflectance 0.50 0.50 0.50
Top Layer Leaf scatterer transmittance 0.44 0.44 0.44
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Planophile Planophile Planophile
Bottom Layer Leaf scatterer reflectance 0.48 0.48 0.48
Bottom Layer Leaf scatterer transmittance 0.48 0.48 0.48
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.16 0.16 0.16

Experiment identifier tag <EXP> : HOM26_DIS_EAP_RED_50 HOM27_DIS_EAP_RED_50 HOM28_DIS_EAP_RED_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Top Layer Leaf scatterer reflectance 0.04 0.04 0.04
Top Layer Leaf scatterer transmittance 0.04 0.04 0.04
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Planophile Planophile Planophile
Bottom Layer Leaf scatterer reflectance 0.06 0.06 0.06
Bottom Layer Leaf scatterer transmittance 0.02 0.02 0.02
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.13 0.13 0.13

Experiment identifier tag <EXP> : HOM26_DIS_EAP_NIR_50 HOM27_DIS_EAP_NIR_50 HOM28_DIS_EAP_NIR_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Top Layer Leaf scatterer reflectance 0.50 0.50 0.50
Top Layer Leaf scatterer transmittance 0.44 0.44 0.44
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Planophile Planophile Planophile
Bottom Layer Leaf scatterer reflectance 0.48 0.48 0.48
Bottom Layer Leaf scatterer transmittance 0.48 0.48 0.48
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.16 0.16 0.16

The next set of two-layer plane-parallel discrete experiments refers to a vegetation canopy with a top layer having a thickness of 1m, a planophile leaf normal distribution, a scatterer radius of 0.05 m, and a Leaf Area Index of 1 m² ⁄ m². The bottom layer features an erectophile leaf normal distribution, identical scatterer radius (0.05m) and height (1m) as the top layer, and three different LAI values (1, 2 and 5 m² ⁄ m²). The overall canopy height is 2m. The scattering laws of (both sides of the) foliage elements and the background surface are Lambertian. Two spectral bands (red and NIR) and two illumination conditions (direct only with SZA=20° and 50°) are proposed for each one of the above three structural scenarios, referred to as HOM36, HOM37 and HOM38 in the tables below.

For 3D RT models capable of using the deterministic position and orientation of all scatterers in the scenes three ASCII files are provided that contain the layer ID (TLL=top layer leaf and BLL=bottom layer leaf), the leaf/disc radius (R), the leaf/disc centre coordinates (Xc,Yc,Zc), and the direction cosines (Dx,Dy,Dz) of every single leaf/disc in a 25×25 m² canopy section. The size of these ASCII files is several Mbytes and the format of its content is R Xc Yc Zc Dx Dy Dz. The deterministic foliage location and orientation information can be found via the next three links: HOM36 (20.7 Mbytes), HOM37 (10.4 Mbytes), and HOM38 (6.9 Mbytes).

Experiment identifier tag <EXP> : HOM36_DIS_PAE_RED_20 HOM37_DIS_PAE_RED_20 HOM38_DIS_PAE_RED_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Planophile Planophile Planophile
Top Layer Leaf scatterer reflectance 0.04 0.04 0.04
Top Layer Leaf scatterer transmittance 0.04 0.04 0.04
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Bottom Layer Leaf scatterer reflectance 0.06 0.06 0.06
Bottom Layer Leaf scatterer transmittance 0.02 0.02 0.02
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.13 0.13 0.13

Experiment identifier tag <EXP> : HOM36_DIS_PAE_NIR_20 HOM37_DIS_PAE_NIR_20 HOM38_DIS_PAE_NIR_20
Solar Zenith Angle (SZA) 20 [deg] 20 [deg] 20 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Planophile Planophile Planophile
Top Layer Leaf scatterer reflectance 0.50 0.50 0.50
Top Layer Leaf scatterer transmittance 0.44 0.44 0.44
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Bottom Layer Leaf scatterer reflectance 0.48 0.48 0.48
Bottom Layer Leaf scatterer transmittance 0.48 0.48 0.48
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.16 0.16 0.16

Experiment identifier tag <EXP> : HOM36_DIS_PAE_RED_50 HOM37_DIS_PAE_RED_50 HOM38_DIS_PAE_RED_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Planophile Planophile Planophile
Top Layer Leaf scatterer reflectance 0.04 0.04 0.04
Top Layer Leaf scatterer transmittance 0.04 0.04 0.04
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Bottom Layer Leaf scatterer reflectance 0.06 0.06 0.06
Bottom Layer Leaf scatterer transmittance 0.02 0.02 0.02
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.13 0.13 0.13

Experiment identifier tag <EXP> : HOM36_DIS_PAE_NIR_50 HOM37_DIS_PAE_NIR_50 HOM38_DIS_PAE_NIR_50
Solar Zenith Angle (SZA) 50 [deg] 50 [deg] 50 [deg]
Solar Azimuth Angle (SAA) 0 [deg] 0 [deg] 0 [deg]
Top Layer Leaf Area Index 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Top Layer Scatterer Normal Distribution Planophile Planophile Planophile
Top Layer Leaf scatterer reflectance 0.50 0.50 0.50
Top Layer Leaf scatterer transmittance 0.44 0.44 0.44
Bottom Layer Leaf Area Index 5.0 [m² ⁄ m²] 2.0 [m² ⁄ m²] 1.0 [m² ⁄ m²]
Bottom Layer Scatterer Normal Distribution Erectophile Erectophile Erectophile
Bottom Layer Leaf scatterer reflectance 0.48 0.48 0.48
Bottom Layer Leaf scatterer transmittance 0.48 0.48 0.48
Scatterer Radius (Top + Bottom layer) 0.05 [m] 0.05 [m] 0.05 [m]
Canopy Height = (Top + Bottom layer widths) 2 = 1 + 1 [m] 2 = 1 + 1 [m] 2 = 1 + 1 [m]
Foliage + background scattering law
Lambertian Lambertian Lambertian
background reflectance
0.16 0.16 0.16


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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