Soil Adjusted Vegetation Index is sort of a hybrid between ratio-based indices and perpendicular indices. This index recognizes that the isovegetation lines do not run along side one another nor do they necessarily converge to a single point. It is a way to correct for the impact of soil line disparities on two-band vegetation indices (Red, NIR). SAVI is calculated with the following formula:
SAVI = (1 + L) * (Bnir – Bred) / (Bnir + Bred + L) L represents the correction (ranges between 0-1) for high vegetation cover (1) or very low vegetation cover (0). Most use .5 for middle of the range. Bnir and Bred are the two bands of light wavelengths. The L constant used for correcting the noise of the differing light reflectance factors among the soil variations can be difficult to accurately determine.
(Last Edit 12 Feb 2023, Kellee)