Question

In remote sensing, what does a Digital Number (DN) represent?

• A. Actual physical radiance value with units
• B. Continuous analog signal from the sensor
• C. Quantized digital value of the detected signal without physical units
• D. Geographic coordinates of a pixel

Hint:

Remember: \[ \boxed{ \text{DN} \rightarrow \text{Quantized digital sensor value} } \] Radiometric calibration converts DN values into physical quantities such as radiance or reflectance.

Answer 1

The Correct Option is C

Concept: A Digital Number (DN) is the integer value assigned to the electromagnetic energy detected by a sensor after analog-to-digital conversion. It has no physical units and must be calibrated to obtain radiance or reflectance.

Step 1: Understand DN values. DN values are stored as integers such as \[ 0\text{--}255,\quad 0\text{--}1023,\quad 0\text{--}4095 \] depending on the sensor's bit depth.

Step 2: Identify the correct definition. Hence, \[ \boxed{\text{DN is a quantized digital value without physical units}.} \] Therefore, the correct option is \[ \boxed{(C).} \]