The MODIS sensors aboard the twin satellites Aqua and Terra provide global coverage of earth’s surface every 1 to 2 days. MODIS’s spatial, spectral, and temporal resolution allow for imagery to be utilized for regional monitoring of vegetation, land surface temperature, and the environment. MODIS data is available for Terra (daily, 8 day, or 16 day composites), Aqua (daily, 8 day, or 16 day composites), and composite of Terra/Aqua 16 day using at surface reflectance data.
Normalized Difference Water Index (NDWI) (NIR/SWIR1) provides information on vegetation liquid water contents and water inundation. It typically ranges from -0.1 to 0.4 for green vegetation where larger values indicate higher water content. This index is useful for comparing water content among vegetation with similar scattering properties (Gao 1996).
NDWI (NIR/SWIR1) uses the normalized difference between the near infrared (NIR) and short wave infrared 1 (SWIR1) bands following (NIR-SWIR1)/(NIR+SWIR1). This method is sensitive to water changes in vegetation canopy and water inundated areas (Gao 1996).
Near Infrared (NIR): 0.841-0.876 μm
Short Wave Infrared 1 (SWIR1): 1.628-1.652 μm
Period of Record
Gao, B.C., 1996, NDWI – A normalized difference water index for remote sensing of vegetation liquid water from space. Remote Sensing of Environment, 58, 257–266.
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