Table 1 Summary of the data processing models and strategies

Constellation

All available satellites of GPS, GLONASS, Galileo, Inclined Geo-Synchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites of BeiDou-2 Navigation Satellite System (BDS-2) and BeiDou-3 Navigation Satellite System (BDS-3); about 119 satellites in total

Observation

Undifferenced ionosphere-free linear combination of code and phase measurements on GPS L1/L2, GLONASS L1/L2, Galileo E1/E5a and BDS-2/BDS-3 B1I/B3I

Time span

From January 1st of 2020 to June 30th of 2022

Sample rate

PCE procedure is 30 s; otherwise, 300 s

Session length

24 h

Cutoff elevation

7°

Weighting

A priori precision of 0.3 m and 0.002 m for raw code and phase observations; elevation (e) dependent, i.e., 1 for e ≥ 30°, otherwise, 2sin(e)

Estimator

LSQ in the batch mode

Perturbation force models

Earth gravity

Earth Gravitational Model 2008 (EGM2008) (12 × 12) (Pavlis et al., 2012)

N-body gravity

Sun, moon and planets with coordinates from Jet Propulsion Laboratory (JPL) Development Ephemerides (DE405) ephemeris (Standish, 1998)

Ocean tide

Finite Element Solution 2004 (FEL2004) tide model (Lyard et al., 2006)

Tide forces and relativistic effects

Models refer to IERS conventions 2010 (Petit & Luzum, 2010)

Earth radiation pressure

Models refer to Rodriguez-Solano et al. (2012b)

Antenna thrust

Models refer to Steigenberger et al. (2018)

Solar Radiation Pressure (SRP)

The box-wing model is taken as initial values for Galileo satellites (Rodriguez-Solano et al., 2012a), while no initial values are applied to GPS, GLONASS and BDS satellites. Empirical CODE (Center for Orbit Determination in Europe) Orbit Model 2 (ECOM2) model is adopted for all satellites (Arnold et al., 2015)

Empirical acceleration

Not considered

Error correction models

Satellite and receiver phase center

PCO and PCV are corrected using values from igs14_2194.atx (Rebischung & Schmid, 2016)

Tide displacement

Corrected considering solid Earth tides, ocean loading, and polar tides; refer to IERS conventions 2010

Relativistic effect

Corrected via IERS conventions 2010

Phase windup

Corrected via Wu et al. (1993)

Parameter estimation strategies

Receiver coordinate

Estimated as 24 h constants; tightly constrained to the IGS weekly solution in the POD and PCE procedure; loosely constrained to its initial value with priori noise of 10 m in the POS procedure; the NNT and NNR conditions are applied in the GCC procedure (Zajdel et al., 2019)

Satellite orbit

Initial position and velocity are estimated as 24 h constants in the POD and GCC procedure

SRP

ECOM2 model with 9 parameters estimated as 24 h constants in the POD and GCC procedure

ERP

Polar motion, polar motion rate and Length of Day (LOD) are estimated as 24 h constant with priori noise of 3″, 0.3 (″)/d and 0.02 s/d respectively, while UT1-UTC is fixed to the IERS C04 products in the POD procedure; all ERP values are fixed to the IERS C04 products in the GCC procedure

Geocenter motion

Estimated as 24 h constants in the GCC procedure

Receiver clock error

One clock value estimated as white noise; refers to GPS time

Satellite clock error

Estimated as random walk

Inter-system bias

One parameter for each system except for GPS, and estimated as 24 h constants

Inter-frequency bias

Estimated as constants for each satellite-station pair for GLONASS

Troposphere delay

Priori value using Saastamoinen model (Saastamoinen, 1972) with meteorological parameters from Global Pressure and Temperature 2 (GPT2), Vienna Mapping Functions 1(VMF1) (Boehm et al., 2006; Lagler et al., 2013); wet ZPD is estimated as 1 h constant and horizontal gradients are estimated as 24 h constants in the POD, PCE and GCC procedure; both wet ZPD and horizontal gradients are estimated as 300 s constants for ZPD products

Ambiguity

Estimated as constants for each continuous arc; double-differenced ambiguity resolution for GPS, Galileo and BDS in all procedures except for the PCE