Accuracy of PPP along with the development of GPS, GLONASS and Galileo

<p>In recent years, one can notice a significant development of the PPP, which both increases accuracy and speeds up the convergence time of the receiver position. New or improved computational algorithms have been developed. This development can also be seen in real-time measurements made possible by the IGS RTS. Other new trends are the development of PPP-AR and the use of cheap receivers such as smartphones. However, the development of the PPP method can be particularly seen in multi‑GNSS measurements. This applies to the continuous development of existing GPS and GLONASS systems and the emergence of new Galileo and BDS systems that have a significant impact on PPP. The development of multi GNSS will increase the number of satellites observed, which improves geometry and PDOP, and increases product accuracy or increases the number of available signals and frequencies. The use of multi-GNSS is possible thanks to the IGS MGEX.</p><p>This research shows how the accuracy and convergence time by the PPP changes with the development of GPS, GLONASS and Galileo systems. We used the globally distributed MGEX stations for three different weeks, each one from 2017, 2018 and 2019. The analysis was made for different constellations: GPS, GLONAS, Galileo, GPS+GLONAS, GPS+Galileo, GLONASS+Galileo and GPS+GLONASS+Galileo for different cut-off elevation angles: 0⁰, 5⁰, 10⁰, 15⁰, 20⁰, 25⁰, 30⁰, 35⁰ and 40⁰.</p><p>Based on the analysis, we show a progressive improvement of accuracy and a shortening of convergence time in recent years. This is especially visible for calculations with multi-GNSS, obtaining the best results for GPS+GLONASS+Galileo for the last analysed period. Already in 2019 on average, about 22 satellites were observed using a total of three systems together. It has also been shown that in 2019, the Galileo system already allows for positioning with high accuracy anywhere on Earth. On average, around 7 Galileo satellites were observed in 2019, where in 2017 on average, fewer than 5 satellites were observed. It has also been shown that the GPS still provides the highest accuracy and has the greatest impact on multi-GNSS positioning accuracy. Even for the GLONASS+Galileo, poorer accuracy was obtained than for GPS‑only. However, for the GLONASS+Galileo solution, a smaller error distribution and lower standard deviation values were obtained than for GPS-only. This may indicate constant bias-related error values (IFB, ISB) and poorer product quality. In addition, for higher elevation angles, it was shown that better accuracy was obtained for Galileo‑only than for GLONASS-only, but only for the third period. It was also noted that for the joint of GLONASS+Galileo, it eliminated errors that occurred in the GLONASS-only, for which, in the second period, much larger errors were obtained than for the other periods. Finally, the influence of multi-GNSS positioning for positioning in constraint conditions was demonstrated by analysing the effect of the elevation angle. It has been shown that even for elevation angle of 40⁰, the use of GPS+GLONASS+Galileo allowed obtaining about 90% of the availability of solutions with accuracy in estimation the position of individual cm.</p>

Estimating and Analyzing Long-Term Multi-GNSS Inter-System Bias Based on Uncombined PPP

With the development of precise positioning with multi-GNSS, the inter-system bias (ISB) has become an issue that cannot be ignored. ISB is introduced from the differences among satellite reference clocks and different receiver hardware delay biases. To analyze the characteristics of multi-GNSS ISB, the precise point positioning (PPP) with full-rank uncombined model was derived for GLONASS, BDS, GALILEO, while the GPS receiver clock was selected as the reference. In addition, a recommended ISB parameter processing model was adopted. Data of 28-days from the Multi-GNSS Experiment (MGEX) station was used to estimate and analyze the ISB parameters. Based on a statistical analysis of the acquired data, results demonstrate that: (a) The rms of multi-GNSS PPP positional bias can reach 4.6 mm, 3.4 mm and 8.5 mm for E, N and U directions, respectively, which guarantees the reliability and accuracy of the ISB parameter solution. (b) The intra-day ISB time series of the three groups is relatively stable with standard deviations less than 0.6 ns. The ISB parameters between the GALILEO and GPS system are the most stable and the standard deviation was the smallest, at about 0.37 ns, which may be related to the good signal quality of the GALILEO system. (c) The mean of the single-day solution of the ISB parameter is not stable and the amplitude of the jump can be up to 60 ns. However, each station shows a similar variation for the same ISB parameter on the same day. The situation is independent of the type of receiver and antenna; however, it may be affected by the satellite reference clock of different systems. (d) There is a clear relationship between the ISB parameters and receiver types.

PPP and PPP-AR Kinematic Post-Processed Performance of GPS-Only, Galileo-Only and Multi-GNSS

Precise point positioning (PPP) has been used for decades not only for general positioning needs but also for geodetic and other scientific applications. The CNES-CLS Analysis Centre (AC) of the International GNSS Service (IGS) is performing PPP with phase ambiguity resolution (PPP-AR) using the zero-difference ambiguity fixing approach also known as “Integer PPP” (IPPP). In this paper we examine the postprocessed kinematic PPP and PPP-AR using Galileo-only, GPS-only and Multi-GNSS (GPS + Galileo) constellations. The interest is to examine the accuracy for each GNSS system individually but also of their combination to measure the current benefits of using Galileo within a Multi-GNSS PPP and PPP-AR. Results show that Galileo-only positioning is nearly at the same level as GPS-only; around 2–4 mm horizontal and aound 10 mm vertical repeatability (example station of BRUX). In addition, the use of Galileo system—even uncompleted—improves the performance of the positioning when combined with GPS giving mm level repeatability (improvement of around 30% in East, North and Up components). Repeatabilities observed for Multi-GNSS (GPS + GAL) PPP-AR, taking into account the global network statistics, are a little larger, with 8 mm in horizontal and 17 mm in vertical directions. This result shows that including Galileo ameliorates the best positioning accuracy achieved until today with GPS PPP-AR.

GALILEO: A Georeferenced System proposed for Emergency Services’ Population Control

Introduction: Overpopulation in emergency services is a problem that can be observed worldwide, and although it has been addressed from different disciplines and perspectives, it still afflicts citizens who are subject to long waiting lists before being attended. Objective: The work here describes the design, development and the first validation of a Web and Mobile georeferenced crowd system for the city of Bogotá, Colombia, oriented to inform and empower the citizen on the population status of the emergency services found in the city. Materials and Method: In this document, we present the architecture, design, and features of the GALILEO System, with results regarding the first validation with citizens of Bogotá, to capture the acceptance and perceived impact of this type of solution in the context in which the System is proposed to function. Results and Discussion: Although GALILEO has not yet been massively implemented in the context for which it is proposed, the results presented here allow us to explore how Information and Communication Technologies (ICT) can be proposed to solve complex social problems, particularly considering the role of the citizen as a source and receiver of information.