Questo layer mappa le alghe galleggianti e la vegetazione acquatica superficiale sui corpi idrici tramite il Floating Algae Index (FAI). Deriva dalle immagini di riflettanza superficiale Sentinel-2 L2A (Copernicus, circa 20 m) elaborate su Google Earth Engine. Valori FAI elevati (dal verde al rosso) indicano film o tappeti algali piu densi sulla superficie dell'acqua, mentre valori bassi (blu) indicano acqua limpida priva di alghe galleggianti.
The Floating Algae Index (FAI) detects floating algae and surface aquatic vegetation on water bodies through a spectral baseline-subtraction technique. Sentinel-2 acquisitions over the selected period are cloud- and shadow-masked using the Scene Classification Layer (SCL), optionally restricted to water pixels, and averaged into a composite; the FAI is then computed per pixel and rendered as a continuous gradient.
| Code | Provider | Resolution | Year |
|---|---|---|---|
| WRD_S2XXX_99 | ESA / Copernicus (Sentinel-2 L2A, COPERNICUS/S2_SR_HARMONIZED via Google Earth Engine) | ~20 m | 2017-present |
FAI = B8A - [B4 + (B11 - B4) * lambda], with lambda = (865 - 665) / (1610 - 665) = 0.211, using the narrow NIR band B8A (865 nm), red B4 (665 nm) and SWIR1 B11 (1610 nm). This baseline subtraction isolates the near-infrared reflectance peak of floating vegetation against the surrounding water (after Hu, 2009).