What data types are provided by the NAVSTAR GPS constellation?

• A. Position, navigation, and timing data.
• B. Position data only.
• C. Timing data only.
• D. Navigation data only.

Answer: (A)

The NAVSTAR GPS constellation provides three intertwined data types that let you know where you are, when you are, and how the satellites are arranged to support that determination. Position data is the user’s actual location in three dimensions, computed by a receiver from measurements to multiple satellites and solving for the receiver’s coordinates and its clock bias. Navigation data is the broadcast navigation message that carries the satellites’ orbital information (ephemeris) and clock corrections, plus almanac data; this information is what enables the receiver to know exactly where each satellite was at a given time and how its clock behaves, which is essential to translate the raw measurements into a position. Timing data is the precise time reference the system provides; GPS time serves as a global clock standard, and receivers align their local clocks to this time as part of solving for position, delivering accurate timing information to users as well. Since all three aspects—where you are, how the satellites are positioned, and what time it is—are interdependent in GPS, the complete set of data includes position, navigation, and timing.