Which of the following vegetation indices is/are designed to jointly address the issues of atmospheric effect, background soil effect, and vegetation saturation effect?
Show Hint
Think about which index adds a blue-band aerosol correction term on top of the SAVI soil correction.
Step 1: List the three named problems and match each to a design feature. Atmospheric effect, soil background effect, and saturation effect are three separate error sources in optical vegetation indices, and the question asks which single index tackles all three at once. Step 2: Rule out NDVI directly from its formula. $NDVI = \dfrac{NIR-Red}{NIR+Red}$ uses only two bands and applies no atmospheric correction term, no soil-brightness term, and its ratio form is known to saturate at high chlorophyll and biomass levels. It addresses none of the three issues by design. Step 3: Rule out SAVI and LAI. SAVI adds only a soil-brightness constant $L$ to the NDVI-type ratio, so it corrects soil background but has no aerosol term and still saturates, addressing only 1 of the 3 issues. LAI is a physical canopy structure quantity, not a corrective spectral index; it is usually estimated using EVI or NDVI, and by itself corrects nothing. Step 4: Confirm EVI covers all three by its formula. \[ EVI = G\left(\dfrac{NIR-Red}{NIR+C_1Red-C_2Blue+L}\right) \] The $-C_2Blue$ term cancels residual atmospheric aerosol scattering (atmospheric correction), the $+L$ canopy background term suppresses soil reflectance influence (soil correction), and the modified denominator with gain $G$ keeps the index responsive instead of flattening in dense canopies (saturation correction). All three named problems map directly onto a term in the EVI formula. Step 5: Final answer. The only index engineered to address atmosphere, soil background, and saturation together is EVI.\[ \boxed{EVI} \]
