Normalized Difference Water Index (NDWI)
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The NDWI, or Normalized Difference Water Index, is an important tool in remote sensing and has two main meanings. Both indices focus on important water characteristics, although each has specific applications.
- NDWI (Gao, 1996):
- This index was proposed by Bo-Cai Gao in 1996.
- It focuses on monitoring changes in leaf water content.
- It uses NIR (near infrared) and SWIR (short-wave infrared) wavelengths.
- It is important for vegetation analysis in arid regions and for various applications such as agricultural monitoring, rangeland management and fire risk assessment.
- Calculation formula: NDWI=(NIR-SWIR)/(NIR+SWIR). In case of Sentinel-2: NDWI=(B8a-B11)/(B8a+B11) or NDWI=(B8a-B12)/(B8a+B12)
- NDWI (K. McFeeters, 1996):
- This index was proposed by Stuart K. McFeeters also in 1996.
- It focuses on the analysis of water bodies.
- It uses green and NIR spectra.
- Formula for calculation: NDWI=(Green-NIR)/(Green+NIR). In the case of Sentinel-2: NDWI=(B3-B8a)/(B3+B8a)