What is the relationship between pressure altitude and true altitude?

The correct choice emphasizes that pressure altitude is determined based on standard atmospheric conditions and that true altitude represents the actual height of an object above sea level.

Pressure altitude is calculated using a standard atmosphere model, which assumes a specific temperature and pressure at sea level, usually under conditions where the barometric pressure equals 29.92 inches of mercury (Hg). This means that pressure altitude can vary with actual weather conditions since atmospheric pressure changes with weather patterns.

True altitude, on the other hand, is the precise height of an object above mean sea level. It is determined using various methods, with GPS being one of the most accurate, as it considers the actual curvature of the Earth and local atmospheric conditions.

Thus, while pressure altitude serves as a useful reference for pilots and aircraft navigation under standardized conditions, true altitude provides the real elevation above sea level, reflecting the actual position in three-dimensional space. Recognizing this relationship allows pilots to safely navigate and account for altitude adjustments in varying atmospheric conditions.