Final answer:
Amelia Earhart and Fred Noonan could refer to celestial navigation with stars and radio communication with ground stations to navigate their flight. GPS was not available during their time, and road maps would not have been useful over the open ocean.
Step-by-step explanation:
In the context of early aviation history, Amelia Earhart and Fred Noonan would have relied on traditional navigation methods during their flights, as modern GPS and satellite technology were not yet available. The two options they could refer to navigate their flight would be:
- Celestial navigation using the stars and other astronomical objects. This includes finding latitude by observing the Pole Star or the position of the noontime Sun, and determining longitude using chronometers synced with broadcast time signals from radio communication with ground stations.
- Radio communication with ground stations, which, after the advent of radio technology in the early 20th century, allowed for resetting shipboard timepieces in accordance with broadcast time signals, crucial for accurate longitude positioning.
Road maps and landmarks (c) would not have been practical options for aerial navigation over open ocean, and GPS and satellite technology (b) were not available during the time of Earhart and Noonan's flights.