NDVI

NDVI, the Normalized Difference Vegetation Index, is a simple remote sensing measure used to assess vegetation health and vigor. It uses the difference between near-infrared (NIR) and red reflectance from satellite imagery to quantify vegetation signal. The index is computed for each pixel as NDVI = (NIR − Red) / (NIR + Red). Typical spectral bands used are red around 0.63–0.69 μm and NIR around 0.76–0.90 μm.

NDVI data come from various satellite sensors that provide red and NIR bands, such as Landsat, Sentinel-2, and MODIS, as well as commercial platforms. NDVI can be derived from any calibrated image with compatible spectral bands, enabling time series analysis to monitor vegetation dynamics over large areas.

Interpretation of NDVI values follows a general scale: the index ranges from −1 to 1. Values near 1 indicate dense, healthy green vegetation; values around 0 indicate sparse vegetation or bare soil; negative values often correspond to water, snow, or clouds. In dense canopies, NDVI can saturate and lose sensitivity to further increases in biomass.

Applications include agricultural monitoring (crop vigor and stress), drought detection, forest health assessment, land cover classification, and phenological studies. Time-series NDVI supports trend analysis, anomaly detection, and regional planning.

Limitations include sensitivity to atmospheric conditions and lighting, soil background effects, and mixed pixels in heterogeneous landscapes. NDVI is not a direct measure of vegetation cover or biomass and may require ground truth for calibration. Sensor differences and atmospheric correction can affect cross-scene comparability. To address some limitations, alternative indices such as EVI, SAVI, and MSAVI are sometimes used, but NDVI remains widely adopted for its simplicity and broad compatibility.