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) (SWIR1/Green) is a water index which provides information on the extent of small turbid ponds (Lacaux 2007) or larger water bodies. This product typically ranges from -0.25 to 1 where water is typically below 0 (Özelkan 2020).
NDWI (SWIR1/Green) is the normalized difference between the short wave near infrared 1 (SWIR1) and green bands following the equation (SWIR1-Green)/(SWIR1+Green) (Lacaux 2007; Allen et al., 2014). 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 low NDWI over water and a high NDWI over land with high contrast.
Short Wave Infrared 1 (SWIR1): 1.628-1.652 μm
Green: 0.545-0.565 μm
Period of Record
Allen, R., Trezza, R., Tasumi, M., & Kjaersgaard, J. (2014). METRIC: Mapping Evapotranspiration at High Resolution Using Internalized Calibration Applications Manual for Landsat Satellite Imagery. V, 3.
Lacaux, J. P., Tourre, Y. M., Vignolles, C., Ndione, J. A., & Lafaye, M. (2007). Classification of ponds from high-spatial resolution remote sensing: Application to Rift Valley Fever epidemics in Senegal. Remote Sensing of Environment, 106(1), 66-74.
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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