RTS Products

Content Description of the RTS Product Streams

The RTS provides combined GNSS satellite orbit and clock correction, code bias and ionosphere information. In the past IGS RTS correction were formatted according to the RTCM SSR standard for State Space Representation. Because the standard extension for other GNSS beyond GPS and GLONASS is still under development within RTCM, products are provided in the IGS-SSR format. Data streams use the NTRIP protocol. RTS corrected products refer to the International Terrestrial Reference Frame 2020 (ITRF 2020).

Two product streams available in the RTS are combination solutions generated by processing individual Real Time solutions from participating Real-time Analysis Centers (RTAC). The effect of combining the different RTAC results is a more reliable and stable performance than that of any single AC’s product. Operational responsibility for the official combination products lies with the IGS Real-Time Analysis Center Coordinator (RTACC).

The RTS products currently include combined multi-GNSS corrections to the satellite orbits, clocks and code biases as well as combined global ionospheric models (Liu et al. 2021). All product streams are described in more detail below:

• SSR*02IGS1: Multi-GNSS combination product, including SSR corrections for GPS, GLONASS and Galileo satellites. The satellite clocks, estimated by individual Real-Time Analyses Centers (RTACs) are used as pseudo-observations within the adjustment process. In the Kalman Filter approach each observation is modelled as a linear function of three estimated parameters: AC specific offset, satellite specific offset common to all ACs, and the actual satellite clock correction, which represents the result of the combination. These three parameter types differ in their statistical properties. The satellite clock offsets are assumed to be static parameters while AC specific and satellite specific offsets are stochastic parameters with appropriate white noise. The solution is regularized by a set of minimal constraints. A recursive algorithm is used to detect orbit outliers. The combination is done system-wise for the reference signals as specified in the IGS RT Committee and mentioned below. The orbit information is extracted from one of the incoming RTAC solutions. Combining only clock corrections using a fixed orbit reference imposes the potential to introduce analysis inconsistencies. Hence, some a priori corrections are applied before clock combination, to compensate for the inconsistency between master AC and other orbits.
• SSR*03IGS1: Multi-GNSS combination product, including SSR corrections for GPS, GLONASS, Galileo and BeiDou satellites (see the description for SSRA02IGS1/SSRC02IGS1 above).
• IONO00IGS1: Real Time combined VTEC Global Ionospheric Model in IGS-SSR format (spherical harmonics to degree 15), with a temporal resolution of 20 minutes. The combination is performed by UPC from solutions provided by a number of Real Time Ionospheric Analysis Centers.
• IONO01IGS1:Real Time combined VTEC Global Ionospheric Model in IGS-SSR format (spherical harmonics to degree 15). The combination is performed by CAS.

The RTS products are disseminated in the form of IGS-SSR streams. The technical content of the RTS products is described in the table below.

References

Banville S., Geng J., Loyer S., Schaer S., Springer T., Strasser S. (2020) On the interoperability of IGS products for precise point positioning with ambiguity resolution. Journal of Geodesy. 94, 10 (2020). https://doi.org/10.1007/s00190-019-01335-w

Liu, Q., Hernández-Pajares, M., Yang, H., Monte-Moreno, E., Roma-Dollase, D., García-Rigo, A., Li, Z., Wang, N., Laurichesse, D., Blot, A., Zhao, Q., Zhang, Q., Hauschild, A., Agrotis, L., Schmitz, M., Wübbena, G., Stürze, A.,  Krankowski, A., Schaer, S., Feltens, J., Komjathy, A.,and Ghoddousi-Fard, R. (2021). The cooperative IGS RT-GIMs: a reliable estimation of the global ionospheric electron content distribution in real time. ESSD, 13 (9), 4567-4582. doi: 10.5194/essd-13-4567-2021 

Wang N., Li Y., Li Z., Liu A., Liu B. (2025) Determination of multi-GNSS differential code biases with satellite antenna phase center corrections. GPS Solutions 30, 22 (2026). https://doi.org/10.1007/s10291-025-01983-w