Table 2
Summary of the processing strategy and correction models depending on the adopted positioning model.
| Parameter | PPP positioning | RTK positioning |
|---|---|---|
| Functional model | SF-IF PPP | ionosphere-float kinematic relative positioning |
| Observation | GRAPHIC LC of GPS carrier-phase and pseudorange | DF DD carrier-phase and pseudorange |
| Observable weighting scheme | An elevation-dependent scheme based on the cosecant function | |
| Zenith-referenced a priori sigma of observables | Pseudorange 30 cm; carrier-phase 3 mm | |
| Elevation cut-off angle | 10° | |
| Sampling interval | 30 s | |
| Satellite orbits and clock products | Precise final provided by IGS | |
| Receiver clock | Estimated as a white noise-like parameter | Eliminated due to double-differencing |
| Satellite code biases handling | Corrected with CODE products (Villiger et al., 2019) | |
| Tropospheric delay handling | A priori corrections from Saastamoinen’s (Saastamoinen, 1973) model and GMF mapping function (Boehm et al., 2006); Wet Zenith Tropospheric Delays are estimated | |
| Ionospheric delay handling | Eliminated with GRAPHIC LC | DD ionospheric delays are estimated as loosely constrained parameters |
| Ambiguity handling | Estimated as float constants over each continuous observation arc | estimated and fixed to integers with MLAMBDA (Chang et al., 2005) and validated with W-ratio (Wang et al., 1998) |
| Parameter estimation method | Kalman filter | |
| Station coordinate handling | Static | Kinematic |
| Antenna phase center offsets and variations | Corrected with Antex igs14.atx (Rebischung et al., 2016) | |
| Relativistic effects, tides, phase wind-up effect | Corrected (Kouba, 2015; Wu et al., 1992) | |
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