In a satellite assisted navigation system (GNSS/GPS), a position line is obtained by?

In a satellite-assisted navigation system, the correct way to determine a position line is by the aircraft's receiver measuring the time difference between signals received from a minimum number of satellites. This method takes advantage of the fact that the distance between a satellite and the receiver can be calculated based on the speed of light and the time it takes for the signal to travel.

When an aircraft receives signals from at least four satellites, the receiver can triangulate its position by calculating how long each signal took to reach it. This time difference allows for the determination of distances from each satellite to the aircraft. With the necessary algorithms, the receiver can then solve the equations generated by these distances to pinpoint the aircraft's location in three-dimensional space.

This process is critical because it enables accurate positioning that is essential for navigation, especially in aviation. The other choices would lead to misunderstandings about how satellite positioning works since they don't effectively describe the multi-satellite time difference measurement that's fundamental to GNSS/GPS navigation.