What aspect does NDVI primarily assess?

The normalized difference vegetation index (NDVI) is primarily used to assess vegetation health and density. This index is calculated using the reflectance values of red and near-infrared light, which are critical indicators of plant photosynthesis and overall vigor. Healthy vegetation absorbs visible light for photosynthesis, while it reflects a significant amount of near-infrared light. By comparing these reflectance values, NDVI provides a quantifiable measure that can indicate the density and health of vegetation in a given area.

Higher NDVI values indicate denser, healthier vegetation, while lower values suggest stress or less dense vegetation. This makes NDVI an essential tool in remote sensing for monitoring changes in vegetation over time, assessing agricultural productivity, and evaluating ecological health. By focusing specifically on plant life, NDVI does not directly assess other aspects like water quality, soil moisture, or urban development, which involve different measurement parameters and techniques.