Table 2 Processing strategy of the pseudorange bias estimation

Step I: linear combination of the pseudorange bias retrieval

Observations

BDS B1I, B3I, B2I, B1C, and B2a pseudorange and carrier phase measurements with the sampling rate of 30 s

Satellite orbit

Fixed by broadcast ephemeris

Stochastic model

Elevation-dependent weighting with a priori precision of 0.003 and 0.3 m for code and phase observations in the zenith direction, respectively

Slant ionospheric delay

Estimated as the white noise (1 × 10⁵ m²/s)

Receiver pseudorange bias variation

Estimated as the random walk (1 × 10⁻⁹ m²/s)

Multi-frequency IFB

Estimated as the random walk (1 × 10⁻⁹ m²/s)

Ambiguities

Estimated as the random walk (1 × 10⁻⁹ m²/s)

Estimator

Kalman filter

Step II: pseudorange bias estimation

Stochastic model

Variance from GF function models

Global ionospheric modeling function

Spherical harmonic function with 15 orders and 15°

Global ionospheric modeling coefficients

Estimated as the random walk (1 × 10⁻² m²/s)

Receiver pseudorange bias

Estimated as the random walk (1 × 10⁻¹¹ m²/s)

Satellite pseudorange bias

Estimated as the random walk (1 × 10⁻¹¹ m²/s)

Estimator

Kalman filter