RTS Monitoring

RTS Monitoring

RTS SSR Product Monitoring

The IGS RTS provides access to real-time precise products such as orbits, clocks, code and phase biases, which can be used as a substitute for ultra-rapid products in real-time applications. Their performance is assessed by the RTACC in two ways: daily comparisons with precise rapid products, and a quality control of all streams in real time.

Reference products. The daily comparisons use the GFZ MGEX rapid products (Deng et al. 2017) with the following satellite clock reference observables:

Combined products. To satisfy high demands on availability and reliability, the RTACC provides two combined multi-GNSS product streams:

• SSRA02IGS1/SSRC02IGS1 (GPS, GLONASS, Galileo)
• SSRA03IGS1/SSRC03IGS1 (GPS, GLONASS, Galileo, BeiDou)

They are computed with the Kalman filter combination of the BKG Ntrip Client (BNC), which deals with outages and offsets of the individual RTAC solutions. The combination approach is described on the Products page.

Comparison method. The real-time corrections of each RTAC stream and of the combined products are applied to the broadcast ephemerides and saved by BNC as SP3 and clock RINEX files, separately for CoM (SSRC) and APC (SSRA) streams. These files are compared daily with the GFZ rapid products using BNC’s SP3 comparison:

• Orbits: differences in radial, along-track and cross-track direction; the plots show the 3D RMS.
• Clocks: the clocks of two products differ by an offset common to all satellites of a system per epoch

(the clock datum) and by a constant offset per satellite (different realizations of the satellite clocks and code biases). Both are estimated in a least-squares adjustment and removed. The plots show the standard deviation of the remaining clock differences after reduction of the radial orbit differences.

• Signal-in-space (SIS): SIS = radial orbit difference − clock difference is the part of the orbit and

clock errors that affects the range of a user (Montenbruck et al. 2015). It shows whether the errors of orbits and clocks compensate each other. Two values are given per stream and system:

• SIS RMS, including the constant offset per satellite;
• SIS standard deviation (SIS Sig), about the mean of each satellite – the variable part of the error, which matters most for a PPP user, as constant satellite offsets are largely absorbed by the float phase ambiguities.

A large SIS RMS with a small SIS Sig indicates constant differences per satellite, as is typical between the products of different ACs.

In the following, the satellite orbit, clock and SIS performance of the different constellations is presented for the individual RTAC solutions and for the combined products over the last 30 days: