On what principle is GPS navigation based?

GPS navigation is based on the principle of satellite ranging, which involves measuring the distance from multiple satellites to determine a precise location on Earth. Each GPS satellite continuously broadcasts signals that include the satellite's position and the exact time the signal was transmitted. A GPS receiver calculates the time it takes for the signal to reach it from the satellites. By knowing the speed of light (the speed at which the signals travel), the receiver can determine how far away each satellite is.

To establish a location, the GPS receiver needs signals from at least four satellites. With the distances from these satellites, the receiver uses trilateration to pinpoint its position in three-dimensional space (latitude, longitude, and altitude). This method enables accurate positioning and navigation across the globe.

The other principles listed do not directly describe how GPS functions. Time-difference refers to methods that may involve determining distances based on variations in signal arrival times, which is not the fundamental operation of GPS. Signal reflectivity pertains to how signals bounce off surfaces and is not used in the standard GPS positioning process. Ground fixing suggests a more static or localized reference point system, which does not apply to the satellite-based global navigation system that GPS employs.