What is true altitude?

True altitude is defined as the vertical distance of an aircraft above sea level. This measurement is crucial for navigation and safety, as it provides a consistent reference point that all pilots can use, regardless of terrain. While flying, pilots often need to maintain specific altitudes above sea level to adhere to airspace requirements, avoid obstacles, and ensure safe separation from other aircraft.

Understanding true altitude is essential because it allows pilots to accurately determine their position in relation to the Earth's surface and other flying activities. True altitude is typically determined via barometric pressure readings corrected to standard atmospheric conditions. This differs from other types of altitude references, such as height above ground level (AGL), which would be affected by the surrounding terrain and may vary significantly over a short distance.

Other alternatives, like the height above the nearest obstacle or pressure altitude corrected for temperature, do not provide the global perspective that true altitude offers. By using true altitude, pilots can ensure they are flying at the intended height above a universally understood reference point: sea level.