NDVI Index

  • Normalized Difference Vegetation Index is a satellite-based vegetation index used to measure plant health, density, and greenness.
  • It is one of the most widely used indicators in remote sensing, agriculture, forestry, and climate studies.
  • NDVI works on the principle that healthy vegetation absorbs red light and reflects near-infrared (NIR) light.

Formula

  • NDVI = (NIR − Red) / (NIR + Red)
  • Values range between −1 and +1

Interpretation of NDVI Values

  • +0.6 to +1.0 → Dense, healthy vegetation (forests, well-irrigated crops)
  • +0.3 to +0.6 → Moderate vegetation (grasslands, crops under growth)
  • 0.1 to +0.3 → Sparse vegetation or stressed crops
  • 0 to 0.1 → Bare soil, rocks
  • Negative values → Water bodies, snow, clouds, urban areas

Why NDVI is Important

  • Helps assess crop health and productivity
  • Used for drought monitoring and early warning systems
  • Tracks deforestation and land degradation
  • Supports climate change studies by monitoring vegetation trends
  • Assists in food security analysis and yield estimation

Applications

  • Agriculture
    • Crop condition monitoring
    • Identifying water stress and pest impact
  • Environment & Ecology
    • Forest cover assessment
    • Desertification studies
  • Disaster Management
    • Drought severity mapping
    • Post-flood or wildfire vegetation recovery
  • Urban & Regional Planning
    • Monitoring green cover loss or expansion

NDVI in India

  • Used extensively by ISRO, State Agriculture Departments, and research institutions.
  • Plays a key role in drought assessment, crop insurance (PMFBY), and monsoon impact analysis.
  • Helps monitor vegetation changes in regions like arid Rajasthan, Indo-Gangetic plains, and forest belts.

Limitations of NDVI

  • Saturates in very dense forests, reducing sensitivity
  • Affected by cloud cover, atmospheric conditions, and soil brightness
  • Cannot distinguish between crop types without additional indices
  • Less effective in areas with mixed land cover

Advanced Indices Beyond NDVI

  • EVI (Enhanced Vegetation Index) – better for dense vegetation
  • SAVI (Soil Adjusted Vegetation Index) – reduces soil background effect
  • NDWI – focuses on vegetation water content
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