GPS improvements over the TRANSIT Doppler satellite positioning system include which of the following?

GPS improvements over the TRANSIT Doppler satellite positioning system include which of the following?

• A. Higher accuracy due to atomic clocks and stable ephemeris
• B. Larger number of satellites and global coverage
• C. Civilian-grade C/A code availability
• D. Both A and C are true

Answer: (D)

GPS improves over TRANSIT mainly through two advances: precise timekeeping and civilian accessibility. Atomic clocks on GPS satellites, together with stable ephemeris data, provide highly accurate time references and accurate satellite position information, which dramatically reduces the timing and orbit errors that affect position calculations. This directly boosts positioning accuracy and reliability compared with the Doppler-based TRANSIT system, which relied on less stable timing and orbital data. At the same time, the civilian C/A code made the system openly usable by the public, giving receivers a straightforward way to measure pseudorange and compute position without encrypted signals. While having more satellites and global coverage enhances availability, the improvements most central to GPS are the improved timekeeping/ephemeris accuracy and the public C/A signal, captured by combining these two aspects.

GPS improves over TRANSIT mainly through two advances: precise timekeeping and civilian accessibility. Atomic clocks on GPS satellites, together with stable ephemeris data, provide highly accurate time references and accurate satellite position information, which dramatically reduces the timing and orbit errors that affect position calculations. This directly boosts positioning accuracy and reliability compared with the Doppler-based TRANSIT system, which relied on less stable timing and orbital data. At the same time, the civilian C/A code made the system openly usable by the public, giving receivers a straightforward way to measure pseudorange and compute position without encrypted signals. While having more satellites and global coverage enhances availability, the improvements most central to GPS are the improved timekeeping/ephemeris accuracy and the public C/A signal, captured by combining these two aspects.