What is the purpose of an altimeter setting?

The purpose of an altimeter setting is to adjust a pressure altimeter for atmospheric pressure variations. This is essential in aviation because atmospheric pressure can change with weather systems and altitude. The altimeter setting, typically given in inches of mercury (inHg) or hectopascals (hPa), allows pilots to calibrate their altimeters to ensure accurate altitude readings relative to the standard atmospheric pressure at sea level. Without this setting adjustment, a pilot could misinterpret their true altitude, which can be critical for maintaining safe clearance above terrain and other aircraft.

The other options do not accurately reflect the function of the altimeter setting; radar readings relate to distance measurements rather than altitude, weight determination involves different calculations, and flight distance calculations use navigation techniques rather than altimeter settings. Understanding the proper use of altimeter settings is crucial for flight safety and navigation accuracy.