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WHAT IS NDVI?

July 25, 2021

Satellites can carry one or more sensors These sensors do not sense the entire electromagnetic spectrum but are sensitive to different ranges of frequencies. They can sense parts of the wavelengths of the solar radiation reflected from the Earth surface.

In other words, a multispectral optical sensor can collect data within different visible and infrared wavelength ranges called spectral bands. Visible wavelengths -blue, red, and green- of the solar radiation reflected from vegetation have low to high values and infrared wavelengths can have very high values.

The spectral bands are useful in deriving the Normalized Difference Vegetation Index (NDVI) images, which can detect patterns of change of vegetation across an area.

The value of the NDVI, which is derived from the red and near-infrared bands typically ranges from -1 up to +1. High positive values are associated with denser, healthy vegetation.

Bare soil value is close to zero and negative values indicate water bodies. NDVI images can be used to detect patterns of change of vegetation across an area.

The satellite data comes from the MultiSpectral Instrument (MSI) on board the Copernicus Sentinel-2 satellites.