What does absolute altitude measure?

Absolute altitude refers to the height of an aircraft above the ground level directly beneath it. This measurement is critical for a pilot to maintain safe clearance over terrain and obstacles, especially during takeoff, landing, and when flying at lower altitudes. It is distinct from altitude above sea level, which is known as pressure altitude or true altitude, and it provides important situational awareness regarding the aircraft's proximity to the terrain. Understanding absolute altitude helps pilots assess flying conditions and terrain features, aligning their operational procedures with safety requirements.