Sequoia captures 4 discrete spectral bands (Green, Red, RedEdge, NIR) and 3 non-discrete spectral bands (as part of the RGB imager).
Within the discrete spectral bands…
Green corresponds to the reflected energy in the 530–570 nm spectral band. It is interesting to note that, out of the entire visible spectrum, the greatest reflectance of a plant is in this band. The reflectance peak is at around 550 nm. This spectral band is often strongly correlated with leaf chlorophyll content.
Red corresponds to the reflected energy in the 640–680 nm spectral band. The strong absorption in this band results in low reflectance. Reflectance varies significantly in relation to factors such as biomass, LAI, soil minerals, humidity and plant stress. For most crops this band gives an excellent contrast between the plants and the soil and it is extensively used for compiling most of the vegetation indices in agriculture
Red Edge is a very narrow band (730–740 nm) that corresponds to the rapid change from low Red reflectance to high Near Infrared reflectance. This band is very sensitive to plant stress and provides information on the chlorophyll and nutrient status of plants. Moreover, an increase in the reflectance of this band often results when a plant is under nutrient stress.
Near Infrared, which corresponds to the wavelengths in the 770 nm to 810 nm range, has the strongest reflectance of the bands studied. This band is sensitive to plant vigor and crop type. Pigments such as chlorophyll do not influence the Near Infrared so it is often used to normalize chlorophyll-sensitive wavebands. Moreover, a reduction of the reflectance in this band results when a plant is under stress. Along with the Red spectral band, Infrared is extensively used for compiling most of the vegetation indices in agriculture.