Full of colors
with orthogonal components of water

Concept: We expanded the concept of orthogonal transformations for aquatic systems, for the first time, through a novel approach termed Orthogonal Components of Water (OCW). The OCWs consist of three orthogonal components – “Brightness”, “Greenness”, and “Blueness” – each constructed to amplify key optical features associated with inorganic and detrital particles, phytoplankton, and optically clear waters, respectively.

Impact: These components support the spectral dimensionality reduction from hyperspectral and multispectral bands, spectral unmixing to improve the characterization of spectral composition in water, and can also serve as input features, similar to spectral indices, for aquatic bio-optical modeling.
 
Approach:
The OCW approach was developed using a rigorous selection of endmember spectra from a global hyperspectral dataset (n=12,867) to implement the Gram–Schmidt orthogonalization technique, and then per-component coefficients were derived for seven satellite missions, including PACE OCI hyperspectral, Aqua/Terra MODIS, JPSS1/JPSS2 VIIRS, Sentinel-3 OLCI, Sentinel-2 MSI, Landsat8/9 OLI, and PlanetScope SuperDove. OCW applications were evaluated at regional and global scales, and the results confirmed the reliability of each OCW in reducing spectral dimensionality while preserving interpretability to dominant optical regimes.