What are the two methods of maintaining MOA boundaries without GPS?

The center radial method and pie-in-the-sky method are effective techniques for maintaining Minimum Operational Altitude (MOA) boundaries without relying on GPS.

The center radial method involves using a fixed point from which radii can be drawn to define the boundaries of a MOA. Pilots can maintain awareness of their position relative to this center point by measuring their distance and direction from it, essentially navigating using angular bearings. This method is particularly useful when navigating in areas with well-defined airspace limits that can be referenced visually or via instruments.

On the other hand, the pie-in-the-sky method relies on observable landmarks or waypoints that guide pilots through the designated airspace. By interpreting visual cues from the environment (like geographical features), pilots can stay oriented within the boundary of a MOA. This approach emphasizes using visual references related to the territory above which the MOA is established.

These methods are advantageous when GPS technology is unavailable or unreliable, allowing pilots to maintain situational awareness and boundary adherence effectively.