Question

(Green reflectance - SWIR reflectance) / (Green reflectance + SWIR reflectance) is known as:

• A. \(\text{NDSI} \)
• B. \(\text{NDVI} \)
• C. \(\text{EVI} \)
• D. \(\text{GARI} \)

Hint:

NDSI (Normalized Difference Snow Index) is used to identify snow and ice, leveraging the high reflectance in the Green band and low reflectance in the SWIR band.

Answer 1

The Correct Option is A

Step 1: Understanding the formula. The given equation follows the general normalized difference formula: \[ \text{Index} = \frac{\text{Band} _1 - \text{Band} _2}{\text{Band} _1 + \text{Band} _2}  \] where: - \(\text{Band} _1\) = Green reflectance - \(\text{Band} _2\) = SWIR reflectance 

Step 2: Identifying the index. This formula is used in the Normalized Difference Snow Index (NDSI), which helps in detecting snow and ice cover by using the contrast between green and shortwave infrared (SWIR) reflectance. 

Step 3: Explanation of other indices. - NDVI (Normalized Difference Vegetation Index): Uses NIR and Red bands for vegetation health monitoring. 
- EVI (Enhanced Vegetation Index): Uses NIR, Red, and Blue bands for vegetation assessment. 
- GARI (Green Atmospherically Resistant Index): Uses Green, Red, NIR, and Blue bands for atmospheric correction in vegetation monitoring. 

Step 4: Selecting the correct option. Since the given formula matches NDSI, the correct answer is a. NDSI.