Vegetationsindex

Vegetationsindex is a family of quantitative metrics used in remote sensing to describe the state and dynamics of vegetation by comparing reflectance in different parts of the spectrum. They are widely used in environmental monitoring, agriculture, forestry, and land management to assess greenness, cover, and productivity over large areas and time.

Most indices rely on reflectance captured in the red and near-infrared (NIR) portions of the spectrum. A common form is NDVI, defined as (NIR − Red) / (NIR + Red). Other indices modify this with soil brightness adjustments (e.g., SAVI) or incorporate additional bands (e.g., EVI uses blue, red, and NIR).

Interpretation: higher values typically indicate denser or healthier vegetation, while lower values point to bare soil or non-vegetated surfaces. NDVI ranges roughly from −1 to +1, with values near zero for barren land and near +1 for very lush vegetation. However, saturation can occur in dense canopies, reducing sensitivity.

Data for vegetation indices are produced by satellite sensors such as Landsat, MODIS, Sentinel-2, and VIIRS. Time series of indices enable monitoring of phenology, drought stress, crop development, and land-use change. They are also used in model assimilation and global vegetation productivity assessments.

Limitations include atmospheric effects, varying soil backgrounds, topography, and cloud cover. Indices provide surrogate measures of greenness rather than direct biomass or leaf area, so they are often combined with other data sources for robust assessments.