The document explains the Normalized Difference Vegetation Index (NDVI), which measures the density of green vegetation using distinct wavelengths of light reflected by plants. NDVI is calculated using the formula (NIR - VIS) / (NIR + VIS) and produces values ranging from -1 to +1, where lower values indicate little to no vegetation and values close to +1 indicate high density of green leaves. Chlorophyll in plant leaves absorbs visible light for photosynthesis, while leaf cell structure reflects near-infrared light, making NDVI a useful tool for assessing vegetation health.

1. NDVI
Normalized Difference Vegetation Index

2. NormalizedDifferenceVegetation Index (NDVI)
•Distinct colors(wavelengths) of visible and near-infrared sunlight reflected by
the plantsdetermine the density of green on a patch of landand ocean.
•The pigment in plantleaves, chlorophyll, strongly absorbs visible light (from
0.4 to 0.7 μm) for use in photosynthesis. The cell structure of the leaves, on
the other hand, strongly reflects near-infrared light (from 0.7 to 1.1 μm).
•The more leaves a plant has or the more phytoplankton thereisin the column,
the more these wavelengthsof light are affected, respectively.

3. (courtesy http://earthobservatory.nasa.gov)
NDVI= (NIR — VIS)/(NIR + VIS)
Calculationsof NDVI for a given
pixel alwaysresult in a number
thatranges from minus one (-1)
to plus one (+1)
-- no green leaves gives a value
close to zero.
-- zero means no vegetation
-- close to +1 (0.8 - 0.9)
indicatesthe highest possible
densityof green leaves.