Table 1 Modeling and parameterization strategy for multi-GNSS real-time satellite clock estimation

Observation modelling

Observation

Ionosphere-free combinations of code and phase measurements

Sample rate

5 s

Elevation mask

7°

Weighting

A priori precision of 0.03 cycles and 3.0 m for raw phase and code, respectively. 1 for E > 30 otherwise 2sin(E) where E means the elevation angle

Corrections

Satellite phase center

igs14.atx (Schmid et al., 2016)

Receiver phase center

igs14.atx (PCV of BDS are corrected as GPS)

Phase wind up

Corrected (Wu et al., 1992)

Troposphere a priori model

Saastamoinen model for wet and dry hydrostatic delay with Global Mapping Function (GMF) mapping functions without gradient model (Boehm et al., 2006)

Station displacements

Solid Earth tides, pole tide and ocean tides corrected according to IERS Conventions 2010 (Luzum & Petit, 2012)

Relativistic effects

Corrected (IERS Conventions 2010)

Parameterization

Adjustment method

SRIF

Station coordinate

Fixed to SINEX file or PANDA GPS-only PPP weekly solutions

Satellite orbit

Fixed to predicted orbit determined by PANDA

Receiver clocks

White noise

Satellite clocks

White noise

Ambiguity

Estimated as constant parameters and re-initialized if a cycle slip, loss of lock and other data disruption occurred

Tropospheric delay

Estimated for each station as random walk

ISB/IFB

Estimated as constant with zero mean constraint