How many satellites are required to obtain a GPS fix?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (C)

To obtain a GPS fix, a minimum of four satellites is needed. This is because each GPS satellite provides a position (or range) based on its signal, and the receiver calculates its location by triangulating the signals from multiple satellites.

When three satellites are used, a GPS receiver can determine a two-dimensional position (latitude and longitude) but cannot accurately ascertain altitude, which is crucial for complete three-dimensional positioning. The fourth satellite allows the receiver to solve for the fourth variable, which is time, enabling it to not only determine the exact three-dimensional location but also account for timing discrepancies inherent in the satellite signals and the receiver's clock. Therefore, the requirement for four satellites ensures a complete and accurate GPS fix, integrating all necessary data for precise positioning.