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) (Green/NIR) is a water index which provides information on open water extent. This product typically ranges from -1 to 0.2 where water is typically above 0 (Özelkan 2020). This product is useful for identifying open water to use in estimating water surface area or removal through masking.
NDWI (Green/NIR) is the normalized difference between the green and near infrared (NIR) bands following the equation NDWI = (Green-NIR)/(Green+NIR). Water reflects Green and absorbs NIR electromagnetic radiation while vegetation and soil absorbs Green and reflects NIR electromagnetic radiation (McFeeters 1996). The result is a high normalized difference (ND) over water and a low ND over land with high contrast.
Near Infrared (NIR): 0.841-0.876 μm
Green: 0.545-0.565 μm
Period of Record
McFeeters, S. K. (1996). The use of the Normalized Difference Water Index (NDWI) in the delineation of open water features. International journal of remote sensing, 17(7), 1425-1432.
Özelkan, E. (2020). Water body detection analysis using NDWI indices derived from Landsat-8 OLI. Polish Journal of Environmental Studies, 29(2), 1759-1769.
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