Question Bank • QB_FM_ADV_060 NAT • 2 Marks

Section 2: Farm Machinery

Farm Machinery

Subtopic: Equipment for precision agriculture

Question Statement:

An active optical canopy sensor mounted on a variable-rate fertilizer spreader measures the spectral reflectance of a wheat canopy. The measured reflectance in the Near-Infrared band is $\rho_{\text{NIR}} = 0.58$ and the reflectance in the Red band is $\rho_{\text{Red}} = 0.08$. The Normalized Difference Vegetation Index (NDVI) of the crop canopy is ________ (round off to 2 decimal places).

Answer Key:

0.76

Step-by-Step Solution & Explanation

``` Canopy Spectral Reflectance: Red Absorption: High (Chlorophyll absorption) NIR Reflection: High (Leaf mesophyll scattering) ``` **Step-by-step Calculation:** 1. NDVI Definition Formula: $\text{NDVI} = \frac{\rho_{\text{NIR}} - \rho_{\text{Red}}}{\rho_{\text{NIR}} + \rho_{\text{Red}}}$ 2. Substituting given spectral reflectance values: $\rho_{\text{NIR}} = 0.58, \quad \rho_{\text{Red}} = 0.08$ $\text{NDVI} = \frac{0.58 - 0.08}{0.58 + 0.08} = \frac{0.50}{0.66} = 0.75757 \approx 0.76$
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