The Sentinel program is composed of two satellites (Sentinel 2A, 2B) and was developed to monitor land surface changes in vegetation, the environment, and land cover. Sentinel-2 spatial, spectral, and temporal resolutions allow for imagery to be processed at sufficient spatial and temporal detail that is optimal for field scale land surface monitoring, management, and research. Sentinel-2 datasets are available for Sentinel 2A, 2B, and composite of 2A/2B using top of atmosphere or 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.
Green: 0.560 μm (S2A) / 0.559 μm (S2B)
Short Wave Infrared 1 (SWIR1): 1.6137 μm (S2A) / 1.6104 μm (S2B)
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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