What is True Altitude?

True altitude refers to the height of an object above mean sea level (MSL), which is a standardized reference point used to measure elevation across different geographical areas. This measurement is crucial for aviation as it provides a consistent basis for altitude references, ensuring that aircraft can safely navigate above terrain and other obstacles.

Mean sea level takes into account variations in sea levels due to tides and atmospheric pressure, thus offering a reliable benchmark for pilots, air traffic controllers, and navigational systems. Understanding true altitude is essential for pilots to ensure they maintain appropriate separation from terrain and other aircraft and comply with airspace regulations.

The other options relate to different altitude measurements or conditions. Height above ground level refers to an object's altitude relative to the terrain directly beneath it, while a pressure altimeter measures altitude based on atmospheric pressure, which can vary, making it less reliable for certain navigational purposes. Lastly, an effective altitude during non-standard conditions refers to how altitude may vary under specific weather or pressure conditions, but does not define true altitude itself.