What is absolute altitude?

Absolute altitude is the height of an aircraft or object above the ground or sea level without any reference to any point on the ground. It is typically measured in feet or meters above sea level and is important for navigation, flight planning, and determining safe altitudes during flight. Absolute altitude is different from true altitude, which is measured above a specific reference point on the ground. Aircraft altimeters are instruments that measure absolute altitude by sensing air pressure changes as altitude changes.