What is necessary to estimate your aircraft's position using a known bearing and distance from a ground position?

To estimate your aircraft's position using a known bearing and distance from a ground position, the primary tool required is a radio navigation aid or an ADF (Automatic Direction Finder). These systems allow pilots to determine their location relative to a previously identified point on the ground, such as a radio beacon or NDB (Non-Directional Beacon).

Using a known bearing and distance involves triangulation or radially calculating your position based on the bearing from the source and the distance traveled. ADFs receive radio signals from ground stations and assist in identifying the aircraft's position relative to those signals. This real-time data is crucial in navigation, especially when determining accurate flight paths or nearby airspace.

Other options, such as a flight log entry from a previous flight, may provide historical data but do not assist in determining current position. Charts that display encrypted locations wouldn't provide actionable information for position estimation in real-time. A GPS signal with high accuracy could also help pinpoint your current location, but the question specifically highlights the use of a known bearing and distance, which aligns directly with radio navigation aids. Hence, the use of an ADF or similar system is the most fitting choice for this context.