Normalized-Difference Snow Index (NDSI)
Normalized-Difference Snow Index (NDSI) – normalized difference of two bands (one in the visible and one in the near-infrared or short-wave infrared parts of the spectrum) is used to map snow. Snow is highly reflective in the visible part of the EM spectrum and highly absorptive in the near-infrared or short-wave infrared part of the spectrum, whereas the reflectance of most clouds remains high in those same parts of the spectrum, allowing good separation of most clouds and snow.
The NDSI has a long history. The use of ratioing visible (VIS) and near-infrared (NIR) or short-wave infrared (SWIR) channels to separate snow and clouds was documented in the literature beginning in the mid-1970s by Valovcin (1976, 1978) and also by Kyle et al. (1978). A considerable amount of work on this subject was conducted at, and published by, the Air Force Geophysics Laboratory (AFGL) (e.g., see Bunting and d’Entremont, 1982). The objective of the AFGL work was to discriminate...
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