Until recently, the real-time IGS precise orbit and clock corrections were only available for the predicted part of the ultra-rapid solution. Whereas the accuracy of the ultra-rapid orbit is about 5 cm, the root mean square (RMS) of the respective satellite clock corrections is, unfortunately, about 3 ns (0.9 m). Hence, high accuracy Precise Point Positioning (PPP) applications can be achieved only in post-processing rather than in realtime. With the availability of the IGS real-time service (RTS), it becomes possible to obtain precise satellite orbit and satellite clock corrections in realtime with accuracy better than those of the ultra-rapid products. Recent research has shown that GPS IGS RTS products availability is at least 95 %, which makes it possible to perform real-time PPP with high accuracy. We study the performance of IGS RTS products in PPP by introducing a detailed description and analysis of IGS RTS products, describing the broadcasting of the IGS RTS orbit and clock corrections and their implementation as corrections to the broadcast ephemerides, and analyzing IGS RTS in PPP using several, randomly selected globally distributed IGS stations. It is shown that using IGS RTS products in real-time PPP can improve the solution RMS by about 50 % compared with the solution obtained from the predicted part of the IGS ultra-rapid products.

Precise Point Positioning (PPP) performance is improving under the ongoing Global Positioning System (GPS) modernisation program. The availability of the third frequency, L5, enables triple-frequency combinations. However, to utilise the modernised L5 signal along with the existing GPS signals, P1-C5 differential code bias must be determined. In this paper, the global network of Multi-Global Navigation Satellite System Experiment (MGEX) stations was used to estimate P1-C5 satellites differential code biases ðDCB S P1ÀC5 Þ. Mathematical background for triple-frequency linear combinations was provided along with the resultant noise and ionosphere amplification factors. Nine triple-frequency linear combinations were chosen, based on different criteria, for processing the modernised L5 signal along with the legacy GPS signals. Finally, test results using real GPS data from ten MGEX stations were provided showing the benefits of the availability of the third frequency on PPP solution convergence time and the precision of the estimated parameters. It was shown that triple-frequency combinations could improve the PPP convergence time and the precision of the estimated parameters by about 10%. These results are considered promising for using the modernised GPS signals for precise positioning applications especially when the fully modernised GPS constellation is available. K E Y WO R D S 1. Precise Point Positioning.2. GPS Modernisation. 3. Hardware Delay.

No abstract

In order to take full advantage of the modernized GPS L2C signal, it is essential that its stochastic characteristics and code bias be rigorously determined. In this paper, long sessions of GPS measurements are used to study the stochastic characteristics of the modernized GPS L2C signal. As a byproduct, the stochastic characteristics of the legacy GPS signals, namely C/A and P2 codes, are also determined, which are used to verify the developed stochastic model of the modernized signal. The differential code biases between P2 and C2, DCBP2-C2, are also estimated using the Bernese GPS software. It is shown that the developed models improved the precise point positioning (PPP) solution and convergence time.

Abstract