Absolute altitude refers to which of the following?

Absolute altitude specifically indicates the vertical distance of an aircraft above the terrain directly below it, commonly referred to as "height above ground level" (AGL). This measurement is vital for pilots as it provides information regarding the aircraft's position relative to the ground, which is crucial for avoiding obstacles during flight and landing.

When discussing absolute altitude, it emphasizes the physical distance from the aircraft to the surface, which can change as the terrain varies. For example, flying over mountains, valleys, or urban areas could all yield different absolute altitude readings even if the aircraft's pressure altitude remains constant.

In contrast, other altitude measures such as pressure altitude and true altitude involve references that are based on sea level or standard atmospheric conditions, which are not what absolute altitude indicates. Hence, when pilots refer to their absolute altitude, they are specifically discussing how high they are above the ground, not how that relates to sea level or other atmospheric standards.