In this document we will try to give some comparizon of the two versions of the Illumina model.
| Feature
| v1
| v2
|
| Resolution
| Fixed to 1km with some degradation with distance
| Multilayer/Multiscale from 20m
|
| Point spread function with 1st scattering only
| 
| 
|
| Point spread function with 2nd scattering
| 
| 
|
| Radial comparizon v1 v2
| 
Single scattering
| 
1st and 2nd order of scattering
|
| Line of sight
| Voxels sticked to a fixed 3D grid (1km x 1km x dz)
| Mini voxels of 1m3 with an initial resolution of 19m with a multiplicative factor of 1.12
|
| Modeling grid
| fixed horizontal grid (1 km) plus a fixed exponential vertical grid
| No vertical grid for the line of sight but fixed resolution grid for the calculation of the 2nd order of scattering. That grid is centered on the mean position between the lamp and the line of sight point and is approching a sphere in shape with a resolution of 2.5km. The maximal allowed height is either 35km or the cloud base height.
|
| Ground reflectance
| Variable on each grid point according to the reflectance product of MODIS
| Fixed all over the domain but obtained by combining some typical surface reflectance spectra
|
| Overhead clouds
| Fixed cloud base height per cloud type. Cloud type to be defined by user.
| Cloud base height and cloud type both defined by the user separatly.
Cloud fraction introduced
|
| Topography screening
| -
| Improved horizon blocking scheme
|
| Scattering probability
| -
| Completly new and more accurate scattering probability equations
|
| Extinction
| -
| Completly new and more accurate transmission equations
|
| Solid angles calculations
| Using the coarse fixed 3d grid of the model and some approximations depending of the viewing angle and the vertical layer thickness.
| Accurate calculation using a unity 1m3 volume
|
| Separated cloud radiance printout
| Cloud radiance not separated from the total radiance
| The radiance from clouds and the total radiance is given in the output file
|
| Adding the calculation of the direct radiance radiance
| No direct radiance considered
| Direct radiance both from lamps and from refleting surfaces
|
| Line of sight below horizon
| Minimum elevation angle of 0.5 deg
| Any elevation angle allowed
|
