What role does a magnetic compass play in navigation?

The magnetic compass is an essential tool in navigation, particularly for pilots. Its primary function is to indicate the aircraft's heading in relation to magnetic north. This means that when a pilot reads the compass, they are able to ascertain which direction the aircraft is pointed based on the Earth's magnetic field.

By providing this information, the compass helps in maintaining the desired flight path, ensuring that the aircraft is traveling in the intended direction. This is crucial for navigation, especially when flying in areas where visual references may be limited, such as over oceans or remote terrain.

The other options relate to different navigational instruments or concepts. For instance, measuring altitude is the function of altimeters, airspeed indicators provide airspeed information, and distance to waypoints is generally calculated using navigational systems or GPS rather than a magnetic compass. Thus, the compass's role is specifically tied to determining the aircraft's heading in relation to magnetic north, making it a fundamental piece of equipment for navigators in aviation.