RAMI1 phase
Within this section of the RAMI initiative homogeneous environments have to be simulated where scatterers possess the typical optical properties of vegetation in the red and near-infrared spectral domain. Two types of homogeneous environments are being considered:
Homogeneous environments are typically represented with 1-dimensional models, where the only spatial coordinate represented explicitly is along the vertical.
However, for the case of finite-sized scatterers, the geophysical medium is intrinsically 3-dimensional, since the individual scatterers are oriented finite size objects, even though it may be simulated statistically without an explicit representation of horizontal variations.
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 precise definitions of the required leaf normal distributions and other RT model technicalities. Also read the relevant file naming and formatting conventions that must be adhered to by all participants.
Results for homogeneous scenes are exhibited in the following Figure, which shows the envelope of a series of histograms of local angular model deviation values estimated for viewing conditions in the principal plane (left panels), cross plane (middle panels) and the principal and cross planes together (right panels).
The top, center and bottom panels display the results obtained at the red, the near-infrared and, at the red and near-infrared wavelengths together, respectively. As such, this figure demonstrates the large spread of results delivered by a set of seven BRF models participating.
All except DART performed the experiments suggested for the homogeneous scenes) representative of the community modeling capacity. Almost all graphs reveal the presence of a first well-marked peak extending from about 8 to 12% and 3 to 6% at the red and near-infrared wavelengths, respectively, and a second peak, less intense close to 15% at the red wavelength. The relative increase in model discrepancies at the red wavelength represents presumably the diversity of approaches to address the fundamental plant canopy specific issue of leaf size effects.
The values obtained when estimating the local model deviation at the near-infrared wavelength reflects mainly the difference in the methods used to estimate the multiple scattering components in the plant-soil system.
The following Figure shows the detailed contributions of the individual models to a series of histograms of local angular model deviation values estimated for viewing conditions in the principal plane (left panels), cross plane (middle panels) and the principal and cross planes together (right panels) for the ensemble of discrete homogeneous test cases.
The top, center and bottom panels display the results obtained at the red, the near-infrared and, at the red and near-infrared wavelengths together, respectively.
