- Leaf Area Index - LAI
- Fraction of Absorded PAR - FAPAR
- Fraction of Vegetation Cover - Fcover
- NDVI
- Land Surface Reflectance
- Burnt Areas
- Land Cover
- Land Surface Albedo
- BRDF
- Downwelling Shortwave Radiation
- Downwelling Longwave Radiation
- Land Surface Temperature
- Precipitation
- Soil Moisture
- Water Bodies
- Water Level
The algorithms applied to POLDER-1/ADEOS-1 and POLDER-2/ADEOS-2 data compute the LAI using a neural network, which inverts the radiative transfer model of Kuusk (1995), merged with the PROSPECT model (Jacquemoud et al., 1996) to take into account leaf optical properties, Price (1990)’s functions and the directional Walthall (1985) model to reproduce the spectral and angular properties of soil, respectively. Algorithmic details can be found on the scientific POLDER website. The network input is a single orbit of 11 directional reflectances in 3 spectral bands (565 nm, 670 nm, and 865 nm) and their angular configurations. The output is the LAI estimated for each POLDER track. A simple merging algorithm, with gaussian temporal weighting, averages these retrieved LAI over 30 days to get a monthly value characterizing mainly the central 10-day period.
Monthly maps of POLDER-2 LAI over part of Africa in 2003.
The POLDER-1 and POLDER-2 LAI are included in the product called "Albedo and Vegetation", provided through the POLDER Data Distribution Center. The POLDER-2 LAI has been validated by Medias-France : results are available in a validation report.
References :
Jacquemoud, S., S. L. Ustin, J. Verdebout, G. Scmuck, G. Andreoli and B. Hosgood, Estimating leaf biochemistry using the PROSPECT leaf optical properties model, Remote Sensing of Environment, 56, 194-202, 1996.
Kuusk, A., A fast invertible canopy reflectance model, Remote Sensing of Environment, 51 : 342-350, 1995.
Price, J. C., On the information content of soil reflectance spectra, Remote Sensing of Environment, 33 : 113-121, 1990.
Verhoef, W., Light scattering by leaf layers with applications to canopy reflectance modelling : the SAIL model, Remote Sensing of Environment, 16:125-141, 1984.
Walthall, C. L., J. M. Norman, J. M. Welles, G. Campbell and B. L. Blad, Simple equation to approximate the bidirectional reflectance from vegetative canopies and bare soil surfaces, Applied Optics, 24, 383-387, 1985.
