The estimated kinematic PPP solution in this study relies on the final satellite orbit data. Therefore, the user has to wait around two weeks to get this kind of performance. Thus, it is highly recommended to study the effect of the near real-time solution to the predicted or ultra-rapid satellite products on the performance of the kinematic PPP solution. These satellite products have low-rate satellite clocks. Future research should aim to investigate the stability of the low-rate satellite clocks with a sampling rate of 5 min for different sampling rates for the observation data (e.g. 1 s, 5 s, 30 s, and 5 min). In addition, the solution is needed in this case to implement an interpolation procedure for the satellite clocks to obtain a smoothed solution form those low-rate satellite clocks.
The study of the effect of the interval of the satellite clocks using Bernese GNSS software includes two solutions for the lower-rate satellite clocks. The first solution is the default one, which is carried out using two estimation loops; the first loop aims to check the satellite residuals for specific values. The satellite data that have a higher value than the specific values are marked in the observation files as bad observations. The second loop is running without using these bad observation data. The modified solution aims to deactivate this residual check; in this case, the first and second loops are the same. The research on this point has to be extended to investigate other residual values instead of the specific values that are implemented within the software.
Moreover, the achieved accuracies of the satellite clocks of CODE open the door to investigate the estimated PPP for a higher rate observation data (e.g. 10 Hz). The implemented time stamp in Bernese GNSS software is based on the second interval. Therefore, the sub-second rates are not implemented in the software. This investigation is important for the kinematic trajectories that observed with high speed (e.g. higher than 100 km/hour).
The study is needed to be extended to investigate the performance for the single frequency PPP solution. The assessment should begin firstly for the static observation data and be followed by the kinematic measurements. This increases the research in the direction of the ionosphere delay estimation. The study may start with a single-frequency geodetic antenna and be followed by low- cost antennas.
The study needs to be extended to include the performance of the inertial-aided system to improve the positioning for hydrography. This system is important in order to model the motion of the measurement vessel. It helps to estimate the positions of the trajectory in the area of observation data with gaps.
110 References
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