Estimates of Minor Ocean Tide Loading Displacement and Its Impact on Continuous GPS Coordinate Time Series

Abstract

Abstract:The site displacement due to ocean tidal loading is regarded as one of the largest uncertainties in precise geodetic positioning measurements, among which the effect of minor ocean tides (MOT), except for the 11 main tidal constituents, are sometimes neglected in routine precise global positioning system (GPS) data processing. We find that MOT can cause large vertical loading displacements with peak-to-peak variations reaching more than 8 mm at coastal/island stations. The impact of MOT on the 24-hour GPS solution is slightly larger than the magnitude of MOT loading itself, with peak-to-peak displacement variation at about 10 mm for the horizontal and 30 mm for the vertical components. We also find that the vertical velocity of all the selected stations in the Southwest Pacific was reduced by more than 10% after considering the MOT effect, while stations with weighted root mean square reduced data account for 62%, 59%, and 36% for the up, east, and north components respectively, in particular for most coastal/island stations. Furthermore, MOT correction could significantly reduce the annual signal of the global stacked east component, the near fortnightly and the long-term periodic signals in the up component. The power of some anomalous harmonics of 1.04 cycle per year is also decreased to some extent. These results further proved the benefits of MOT correction in precise GPS data processing.

The Magnitude of Diurnal/Semidiurnal Atmospheric Tides (S1/S2) and Their Impacts on the Continuous GPS Coordinate Time Series

“…However, because we only focus on the difference caused by S1/S2, this disadvantage would not impact the relative coordinate difference much. Moreover, from our experience, a more recent and longer time series would not impact much on the final result, as we did a comparative analysis on the minor ocean tide using both a short time (1999)(2000)(2001)(2002)(2003) and a longer period (1998-2010) [32], and the conclusions were almost the same. Therefore, we think that the experiment here is reasonable and effective.…”

High-order Ionospheric Effects on GPS Coordinate Time Series

“…In our data processing, several parameters are resolved simultaneously, including site coordinates, earth orientation parameters, satellite orbits, tropospheric delay and the horizontal gradient parameters [17]. The stations are given loose constraints, among which the constraints of 5cm are set to IGS core stations, and 1dm to the non-core stations [22]. Ten degree is chosen for the satellite cut-off elevation angle, and the observations are weighted with site-specific, elevation-dependent weighting based on an assessment of the post phase residuals [15,22,38].…”

“…The stations are given loose constraints, among which the constraints of 5cm are set to IGS core stations, and 1dm to the non-core stations [22]. Ten degree is chosen for the satellite cut-off elevation angle, and the observations are weighted with site-specific, elevation-dependent weighting based on an assessment of the post phase residuals [15,22,38]. Corrections have been implemented for solid earth tide, ocean tide and pole tide, among which the FES2004 model is used to calculate site displacement due to ocean tidal loading [23].…”

“…Vienna Mapping Function 1 (VMF1) troposphere mapping functions are used to calculate the tropospheric delay [5]. Atmospheric tidal correction and non-tidal loading corrections are not applied [22,30]. Pressure and temperature for the a priori zenith hydrostatic delay are provided with receiver-independent exchange (RINEX) meteorological files (.m) and values from VMF1 [37].…”

“…Thus, effects of the thermal origin and hydrological dynamics may produce variations in our GPS coordinate time series. Additionally, the thermal noise of the antenna, local multipath effects and model errors such as satellite orbital models, tropospheric delay models and other technique-specific system errors can induce seasonal deformation at the sites [2,12,22,35,42].…”