USNO GPS/GLONASS PNT products: Overview, and GPS+GLONASS vs GLONASS only PPP accuracy

The GPS Analysis Division, Earth Orientation Department, US Naval Observatory processes data from hundreds of carrier-phase GNSS receivers daily, computing 16 product sets/day using measurements from the GPS and/or (Russian) GLONASS satellite systems. Product sets include high-precision satellite orbits and clock corrections, receiver clock corrections, earth-orientation parameters (EOPs), a UT1-UTC extrapolator, and IGS Final Troposphere values for 300+ IGS receiver locations worldwide. The division has maintained a 98-100% on-time rate for all of its products since 2007. Both post-processed (3-16 hour latency) and predicted clocks/orbits/EOPs are produced. Post-processed GPS satellite orbits/clocks have approximately 17 mm/150 ps precision, with predicted GPS satellite orbits/clocks in the 40 mm/2 ns range. Post-processed/predicted GLONASS orbits have 5 and 12 cm precision, respectively. The clock/orbit predictions may be useful for real-time applications. This article consists of two parts. In the first, we summarize the precision and availability of GPS Analysis Division positioning/navigation/timing (PNT) and meteorology products. In the second, we present the results of a test in which we estimate PNT values using the precise-point positioning technique with GPS, GLONASS, and combined GPS and GLONASS measurements.