Question

In case of normalized difference vegetation index (NDVI), which of the following statements is/are correct?

• A. It is functionally equivalent to a simple ratio of red to near infra-red reflectance
• B. It reduces many forms of multiplicative noise
• C. It reduces additive noise
• D. It is sensitive to canopy background variations

Hint:

NDVI is robust against multiplicative effects (like sun angle), but sensitive to background reflectance variations and does not fully suppress additive noise.

Answer 1

The Correct Option is A, B, D

NDVI is defined as:
\[ {NDVI} = \frac{{NIR} - {Red}}{{NIR} + {Red}} \]
Though it is not a simple ratio like \(\frac{{NIR}}{{Red}}\), NDVI and simple ratios provide similar vegetation sensitivity in practice, hence (A) is functionally equivalent and correct.
Since NDVI is a ratio-based index, it reduces the effects of multiplicative noise such as varying sunlight or sensor gain — making (B) correct.
NDVI does not reduce additive noise effectively (e.g., atmospheric path radiance), hence (C) is incorrect.
NDVI values are known to be influenced by soil/canopy background, particularly when vegetation is sparse — making (D) correct.

Final Answer: \(\fbox{(A), (B), (D)}\)