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/SWIR1) is a water index which provides information on open water extent. This product typically ranges from -1 to 0.25 where water is typically above 0.04 (Özelkan 2020). This product is useful for identifying open water to use in estimating water surface area or removal through masking.
NDWI (Green/SWIR1) is the normalized difference between the green and short wave near infrared 1 (SWIR1) bands following the equation NDWI = (Green-SWIR1)/(Green+SWIR1). Water reflects Green and absorbs SWIR1 electromagnetic radiation while vegetation and soil absorbs Green and reflects SWIR1 electromagnetic radiation (Xu 2006). The result is a high normalized difference (ND) over water and a low ND over land with high contrast.
Short Wave Infrared 1 (SWIR1): 1.628-1.652 μm
Green: 0.545-0.565 μm
Period of Record
Özelkan, E. (2020). Water body detection analysis using NDWI indices derived from Landsat-8 OLI. Polish Journal of Environmental Studies, 29(2), 1759-1769.
Xu, H. (2006). Modification of normalised difference water index (NDWI) to enhance open water features in remotely sensed imagery. International journal of remote sensing, 27(14), 3025-3033.
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