spectral-indices

○unverified

Five canonical spectral indices over a named AOI from Sentinel-2 L2A: NDVI, NDSI, NDWI, NBR and BSI. Each is computed per scene, cloud-masked from the scene classification layer, and reduced to a median over the date window. One snapshot per run, not a time series; rerunning on a schedule updates the snapshot. NDVI = (N - R) / (N + R) vegetation greenness (NIR vs red) NDSI = (G - S1) / (G + S1) snow / cloud discrimination (green vs SWIR-1) NDWI = (G - N) / (G + N) surface water (McFeeters; green vs NIR) NBR = (N - S2) / (N + S2) burn severity / health (NIR vs SWIR-2) BSI = ((S1 + R) - (N + B)) / ((S1 + R) + (N + B)) bare soil (SWIR-1 + red vs NIR + blue) On NDSI: this recipe treats snow as a real surface signal rather than something to remove, so nothing here masks the snow class. The platform cloud mask drops cloud, shadow and cirrus only. For snow-cover fraction as a question in its own right, use snow-cover-fsc, which drives per-scene NDSI through a sigmoid calibrated to FSCTOC.