Question

Consider an across-track multispectral scanner with ground pixel size of $56\,$m $\times$ $79\,$m in the along-track and across-track directions. Which of the following statement is TRUE?

• A. Aspect ratio distortion of the image will be greater than 1
• B. Aspect ratio distortion of the image will be less than 1
• C. There will be no geometric distortion in the image
• D. Aspect ratio distortion is a type of radiometric distortion

Hint:

Aspect ratio (AR) $=$ across-/along-track GSD. AR$=1$ $⇒$ square pixel (no aspect ratio distortion); AR$\neq 1$ $⇒$ rectangular pixel (geometric distortion).

Answer 1

The Correct Option is A

The aspect ratio of the ground pixel is defined as \[ \text{AR} = \frac{\text{across-track GSD}}{\text{along-track GSD}} = \frac{79}{56} = 1.41>1. \] Since the ground sampling distances (GSDs) are unequal, the pixel is rectangular and the image exhibits an aspect ratio distortion greater than 1. (B) is false because AR \(>1 \); (C) is false since unequal GSDs imply geometric distortion; (D) is false—aspect ratio is a geometric (not radiometric) effect.