What is indicated by the term "true altitude" in aviation?

The term "true altitude" in aviation refers specifically to the height of an aircraft above mean sea level (MSL). This measurement is critical for ensuring safe vertical separation from terrain and other obstacles, as well as for compliance with air traffic control instructions. True altitude provides a consistent reference point that accounts for variations in atmospheric pressure and temperature, which can affect other altitude readings.

Understanding true altitude is essential for pilots because it allows them to determine their actual position relative to sea level, which is vital for navigating safely, especially in mountainous regions or areas where terrain elevation can vary significantly. The other terms and concepts, such as altitude over ground, altitude corrected for pressure, or indicated altitude, relate to different measurements and are not synonymous with true altitude.