FAA Aircraft Dispatcher Practice Exam

How does GPS work?

1. Using ground-based stations to guide aircraft

2. By triangulating signals from surrounding towers

3. Through the reception of signals from multiple satellites

4. By monitoring aircraft from control towers

The correct answer is: Through the reception of signals from multiple satellites

The Global Positioning System (GPS) operates by receiving signals from multiple satellites that are in orbit around the Earth. Each GPS satellite continuously broadcasts messages that contain the satellite's location and the exact time the signals are transmitted. A GPS receiver, such as one used in aircraft, picks up these signals from at least four satellites to determine its precise position in three-dimensional space (latitude, longitude, and altitude). The process of determining position works through a technique known as trilateration. By measuring how long it takes for a signal to travel from each satellite to the receiver, the receiver can calculate the distance to each satellite based on the speed of light. Once the distances to several satellites are known, the position of the receiver can be accurately determined. This method is highly effective and is why GPS is widely used in aviation, navigation, and various other applications. The alternatives, such as relying solely on ground-based stations or triangulating signals from towers, do not utilize the network of satellites that makes GPS a robust and reliable navigation system.