Why is calibration important for fieldwork instruments?

• A. To calibrate color of graphs.
• B. To align with cartographic scale.
• C. To adjust readings to local time.
• D. To ensure readings are accurate and comparable across devices and times.

Answer: (D)

Calibration ensures readings reflect true values and stay consistent across different devices and over time. In the field, instruments can drift due to factors like temperature, aging, or sensor wear, so calibrating them against a known standard adjusts the measurements to a reliable reference. This makes data accurate and comparable whether you’re using a different instrument or collecting data on different days, which is essential for spotting real changes rather than instrument error. The other ideas don’t fit because calibration isn’t about graph colors, it doesn’t set map scales, and it doesn’t adjust for local time—the concern here is the accuracy and comparability of measurement readings themselves.