What is AGL in Aviation? (Above Ground Level)

In the world of aviation, there are numerous terms and acronyms that may seem perplexing to those who are not familiar with the industry. One such term is “above ground level,” often abbreviated as AGL. Understanding what AGL means and how it is used is crucial for pilots, air traffic controllers, and those involved in aviation operations.

Understanding Above Ground Level (AGL)

Above ground level (AGL) is a measurement in aviation that refers to the altitude of an aircraft or an object above the terrain or ground surface below it. It is an essential metric that helps pilots understand their position relative to the ground during flight. AGL is often used in conjunction with other altitude measurements, such as altitude above mean sea level (AMSL), to provide a comprehensive understanding of an aircraft’s vertical position.

AGL is particularly useful in situations where the elevation of the ground may vary significantly, such as during takeoff and landing. By knowing the aircraft’s altitude above the ground, pilots can ensure a safe and controlled approach to the runway and maintain the required clearance from obstacles like trees, buildings, and terrain features.

An aircraft’s altimeter provides altitude information based on the atmospheric pressure, but this measurement is usually referenced to a specific elevation, such as sea level. Therefore, to determine AGL, the aircraft’s altimeter reading must be adjusted to account for the local terrain elevation.

Using Above Ground Level in Aviation Operations

The concept of AGL is crucial in various aspects of aviation operations. Let’s explore some of the significant areas where AGL is utilized:

Approach and Landing

During approach and landing, it is vital for pilots to have accurate information about the aircraft’s altitude above the ground. This information allows them to determine the correct descent rate and provides awareness of any obstructions that may require additional procedures or adjustments to the approach path.

For example, when conducting a visual approach, pilots are often required to maintain a specific altitude above the ground until reaching a designated point. This altitude is typically expressed as an AGL value, ensuring that the aircraft maintains a safe distance from obstacles or terrain features.

Obstacle Clearance

AGL measurements are crucial for obstacle clearance purposes as well. The minimum required obstacle clearance altitude (MOCA) and minimum obstruction clearance altitude (MOCA) are both referenced to AGL.

MOCA refers to the minimum altitude at which an aircraft can safely fly in certain areas while maintaining sufficient terrain clearance. This altitude is typically calculated based on AGL and is used to ensure that aircraft stay clear of obstacles and terrain within the designated airspace.

Similarly, MOCA provides pilots with the minimum altitude required to ensure safe obstacle clearance during specific flight procedures or in areas with known obstructions. By referencing these altitudes to AGL, pilots can make informed decisions about their flight paths and maintain safe distances from the ground or other obstacles.


Above ground level (AGL) is a critical measurement in aviation that provides valuable information about an aircraft’s altitude above the terrain or ground surface. Pilots and aviation professionals utilize this metric during various phases of flight, including approach and landing procedures, to ensure safe and obstacle-free operations.

By understanding AGL and its significance, both pilots and air traffic controllers can make informed decisions to maintain a high level of safety during flight. With accurate AGL measurements, pilots can confidently navigate the skies while maintaining the necessary clearance from the ground and obstacles.

Remember, when it comes to aviation, understanding the terminology is crucial for effective communication and safe operations. By demystifying terms like AGL, we can ensure a safer and more efficient aviation industry.

For More: What is MFDS in Aviation? (Multi-Function Display System)