Physical Products
The GVPS operationally outputs the following physical parameters in various categories at weekly interval:- Smoothed NDVI (SMN) and Smoothed T (SMT)
SMN: smoothed NDVI with ACDF adjustment
SMT: smoothed AVHRR channel 4 temperature
SMN, SMT: are essentially the NDVI and T but smoothed by a 15-week temporal filter, no atmospheric correction was applied to NDVI and T.
- Green Vegetation Fraction (GVF)
GVF : green vegetation fraction, valued from 0 to 100 percent. For each week, GVF is derived directly from smoothed NDVI by linear scaling:
GVF= (SMN-0.05)/0.44 *100
- Vegetation Health Indices (VCI, TCI and VTI)
VCI=(SMN-NDVImin)/(NDVImax-NDVImin) *100
where, NDVImax, and NDVImin are the multi-year maximum and minimum NDVI for a pixel;
VCI is vegetation condition index, valued from 0 to 100, shows moisture conditions. Lower VCI values indicate less vegetation cover.
TCI=(Tmax-SMT)/(Tmax-Tmin) *100
where, Tmax, Tmin are the multi-year maximum and minimum temperature for a pixel.
TCI is temperature condition index, valued from 0 to 100, shows thermal conditions. Higher values of TCI indicate wetter conditions at surface.
VTI=(VCI+TCI)/2.
VTI is vegetation-temperature index or the so-called "Vegetation Health Index", valued from 0 to 100.VTI is a draught indicator - the lower the value, the drier the surface.