Vegetation variables are important for evaluating the status and temporal processes of vegetated land surfaces. Using the AVHRR reflectance data it is possible to derive such vegetation variables consistently over large regions (regional and continental) and for long time periods.
The Normalized Difference Vegetation Index (NDVI) is an indicator of the greenness of vegetation and thus closely linked to vegetation density and productivity (Tucker & Sellers 1986). The NDVI is calculated using the spectral reflectance measurements of the red and infrared (NIR) wavelength and can range from -1 to +1.
NDVI = (NIR – red)/(NIR + red)
The TIMELINE NDVI is derived from atmospherically corrected and BRD (Bidirectional Reflection Distribution) normalized surface reflectances values from the TIMELINE SR (Surface Reflectance) product.
Example of the NDVI product from August 1990.
Tucker, CJ & Sellers, PJ (1986) Satellite remote sensing of primary production. Int. J. Remote Sens., 7, 1395–1416.