What is the maximum error allowed when comparing indicated altitude to the elevation of a known checkpoint?

The maximum error allowed when comparing indicated altitude to the elevation of a known checkpoint is established to ensure that pilots can maintain safe and accurate altitudes while operating an aircraft. A tolerance of 75 feet is acceptable, reflecting the need for precision in altitude assignments, particularly in environments with air traffic control and proximity to terrain.

This limit is based on both safety considerations and operational efficiency, accounting for variables such as atmospheric pressure changes and altimeter calibration that can affect readings. An acceptable margin allows pilots to make informed decisions without compromising safety when navigating, especially when flying at lower altitudes near checkpoints or during approaches and landings.