Handling method for outages of IGS real-time service (RTS) in GNSS real-time sensing of atmospheric water vapor

The continuity and accuracy of real-time (RT) global satellite navigation system (GNSS) sensing atmospheric water vapor can be seriously affected by a lack connectivity. To mitigate this issue, method has been developed that utilizes the International GNSS Service (IGS) ultra-rapid (IGU) orbit an established RT service (RTS) for clock correction. This ensures estimation even when communication is interrupted. RTS variations in historical correction data from user side to extrapolate its high-precision value. Through experimentation, it determined using quadratic polynomial eighth-order harmonic-based function along with 1-hour optimal establishing method. 2D 3D accuracies static Precise Point Positioning (PPP) achieve centimeter millimeter levels, estimated average Root Mean Square (RMS) zenith tropospheric delay (ZTD) equivalent archived products. When compared precipitable (PWV) results obtained IGS ZTD products, averaged RMS values GPS, Galileo, BDS-3 PWV reach 3.12 mm, 4.41 6.43 respectively, which meet requirements general numerical weather forecasting other applications during interruptions.