The Landsat program provides the longest continuous record of satellite earth observations. Landsat 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. Landsat data is available for Landsat 5, 7, 8, and composites of 4/5/7/8 using top of atmosphere or at surface reflectance data.
Normalized Difference Water Index (NDWI) (Green/SWIR2) 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/SWIR2) is the normalized difference between the green and short wave near infrared 1 (SWIR2) bands following the equation (Green-SWIR2)/(Green+SWIR2). Water reflects Green and absorbs SWIR2 electromagnetic radiation while vegetation and soil absorbs Green and reflects SWIR2 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 2 (SWIR2): 2.08-2.35 μm
Green: 0.52-0.60 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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