True altitude represents:

True altitude refers to the actual height of an object, such as an aircraft, above mean sea level. This measurement is crucial for aviation, as it provides pilots and navigators with a standard reference point to gauge their elevation in relation to sea level, which remains consistent regardless of variations in terrain or atmospheric conditions.

In the context of aviation and weather measurements, understanding true altitude is essential for maintaining safe distances from the ground, especially in areas with varying elevations. Unlike other forms of altitude measurement, such as height above ground level, which can change depending on the local terrain, true altitude is standardized against sea level, making it a reliable reference for navigation and safety.

Other options, while related to altitude, do not provide the same standardized measurement as true altitude does in the context of aviation and meteorology.