What are marker beacons used for?

Marker beacons are specialized radio beacons that are primarily used to indicate the aircraft's position as it approaches a runway during an instrument landing. They provide pilots with important location cues at specific points along the approach path, which enhances situational awareness and aids in navigation during low visibility conditions.

When an aircraft passes over a marker beacon, it typically receives an audio and visual signal in the cockpit, indicating that it is approaching a critical phase of the landing approach, such as the outer marker (often indicating that the aircraft is at the correct altitude to begin the final approach) or the middle marker (indicating that the aircraft is near the decision height). Each of these markers serves a specific purpose in ensuring the aircraft is on the correct path and at the right altitude as it nears the runway.

The other options do not accurately describe the functionality of marker beacons: they do not indicate altitude or heading, nor do they provide weather information. Instead, their intended role is distinctly focused on providing precise positional information during the critical approach phase of flight.