Triple-frequency GNSS models for PPP with float ambiguity estimation: performance comparison using GPS

Deo, Manoj; El‐Mowafy, Ahmed

doi:10.1080/00396265.2016.1263179

Cited by 36 publications

(35 citation statements)

References 26 publications

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“…It was shown that triple-frequency combinations could improve the PPP convergence time and the precision of the estimated parameters by about 10%. Deo and El-Mowafy (2016) presented three triple-frequency PPP models, namely, the triple-frequency code-only and phase-only ionosphere-free model, the mixed code and phase model and the individual uncombined model. By comparison with the traditional dual-frequency model, it was shown that all three triple-frequency models had improved the convergence time (CT) required to achieve and maintain a 3D positional accuracy of 5 cm, by 8%-11%.…”

Section: Introductionmentioning

confidence: 99%

Three-frequency BDS precise point positioning ambiguity resolution based on raw observables

Pan

Zhang

et al. 2018

J Geod

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All Beidou navigation satellite system (BDS) satellites are transmitting signals on three frequencies, which brings new opportunity and challenges for high-accuracy precise point positioning (PPP) with ambiguity resolution (AR). This paper proposes an effective uncalibrated phase delay (UPD) estimation and AR strategy which is based on a raw PPP model. First, triple-frequency raw PPP models are developed. The observation model and stochastic model are designed and extended to accommodate the third frequency. Then, the UPD is parameterized in raw frequency form while estimated with the high-precision and low-noise integer linear combination of float ambiguity which are derived by ambiguity de-correlation. Third, with UPD corrected, the LAMBDA method is used for resolving full or partial ambiguities which can be fixed. This method can be easily and flexibly extended for dual-, triple-, or even more frequency. To verify the effectiveness and performance of triple-frequency PPP AR, tests with real BDS data from 90 stations lasting for 21 days were performed in static mode. Data were processed with three strategies: BDS triple-frequency ambiguity-float PPP, BDS triple-frequency PPP with dual-frequency (B1/B2) and three-frequency AR, respectively. Numerous experimental results showed that compared with the ambiguity-float solution, the performance in terms of convergence time and positioning biases can be significantly improved by AR. Among three groups of solutions, the triple-frequency PPP AR achieved the best performance. Compared with dual-frequency AR, additional the third frequency could apparently improve the position estimations during the initialization phase and under constraint environments when the dual-frequency PPP AR is limited by few satellite numbers.

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Section: Introductionmentioning

confidence: 99%

Three-frequency BDS precise point positioning ambiguity resolution based on raw observables

Pan

Zhang

et al. 2018

J Geod

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“…where λ c and N c represent the IF wavelength and the corresponding ambiguity, respectively. However, the modeling of triple-frequency PPP using two dependent IF linear combinations needs to account for the correlations between observations [21,22]. Moreover, the observation noise is increased for both code and phase observations.…”

Section: Functional Modelmentioning

confidence: 99%

Performance Evaluation of Troposphere Estimated from Galileo-Only Multi-Frequency Observations

2020

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The tropospheric delays estimated from the Global Navigation Satellite System (GNSS) have been proven to be an efficient product for monitoring variations of water vapor, which plays an important role in meteorology applications. The operational GNSS water vapor monitoring system is currently based on the Global Positioning System (GPS) and GLObal NAvigation Satellite System(GLONASS) dual-frequency observations. The Galileo satellite navigation system has been evolving continuously, and on 11 February 2019, the constellation reached 22 active satellites, achieving a capability of standalone Precise Point Positioning (PPP) and tropospheric estimation that is global in scope. This enhancement shows a 37% improvement if the precision of the Galileo-only zenith tropospheric delay, while we may anticipate further benefits in terms of tropospheric gradients and slant delays in the future if an optimal multi-constellation and multi-frequency processing strategy is used. First, we analyze the performance of the multi-frequency troposphere estimates based on the PPP raw observation model by comparing it with the standard ionosphere-free model. The performance of the Galileo-only tropospheric solution is then validated with respect to GPS-only solution using 48 globally distributed Multi-GNSS Experiment (MGEX) stations. The averaged bias and standard deviations are −0.3 and 5.8 mm when only using GPS satellites, respectively, and 0.0 and 6.2 mm for Galileo, respectively, when compared to the International GNSS Service (IGS) final Zenith Troposphere Delay(ZTD) products. Using receiver antenna phase center corrections from the corresponding GPS dual-frequency observations does not affect the Galileo PPP ambiguity float troposphere solutions. These results demonstrate a comparable precision achieved for both Galileo-only and GPS-only ZTD solutions, however, horizontal tropospheric gradients, estimated from standalone GPS and Galileo solutions, still show larger discrepancies, mainly due to their being less Galileo satellites than GPS satellites. Including Galileo E1, E5a, E5b, and E5 signals, along with their proper observation weighting, show the benefit of multi-frequency observations, further improving the ZTD precision by 4% when compared to the dual-frequency raw observation model. Overall, the presented results demonstrate good prospects for the application of multi-frequency Galileo observations for the tropospheric parameter estimates.

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“…Since the float-ambiguity PPP is a positioning method that is characterised by a long initialisation period for convergence of the solution and ambiguities (Deo and El-Mowafy, 2017), two cases were considered to evaluate the impact of using the predicted clocks and IGU orbits. The first case represents a typical scenario, where a break in communications and in receiving the real-time corrections is assumed taking place during normal PPP operation, e.g.…”

Section: The Impact Of Prediction On Ppp Solution Convergencementioning

confidence: 99%

Impact of predicting real-time clock corrections during their outages on precise point positioning

El‐Mowafy

2017

Survey Review

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Real-time Precise Point Positioning (RT-PPP) is a popular positioning method for natural hazard warning systems (NHWS) such as for monitoring tsunami and earthquakes. PPP relays on the use of precise orbits and clock corrections. Hence, the positioning accuracy of RT-PPP will significantly deteriorate when experiencing a discontinuity in receiving these corrections, for instance due to a temporary modem failure. The best available approach in this case would be to use the International Global Navigation Satellite Systems Service (IGS) ultra-rapid (IGU) orbits and clocks that would result in a low positioning accuracy. In this paper, we present a simplified approach to a method that we recently proposed to bridge outages in the corrections and improve the RT-PPP accuracy compared with the use of IGU. In this method, the most recent IGU orbits are used as they are compatible with the RT orbits; however, the clock corrections are predicted as a time series using a linear model with four sinusoidal terms. The prediction errors resulting from this method, age of the model and its validity period are discussed. The impact of using the proposed approach is evaluated at a number of sites of known positions by comparing its performance to using IGU orbits and clocks. Moreover, the impact of using predicted corrections is assessed in different scenarios. The experimental results proved validity of the presented approach where positioning mean RMSE of less than 20 cm was maintained during the outage period.

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Triple-frequency GNSS models for PPP with float ambiguity estimation: performance comparison using GPS

Abstract: He obtained his B.App.Sc and M.Sc degrees in 1998 and 2010, respectively. His current research focus is on precise point positioning with multi-constellation and multi-frequency GNSS.

Cited by 36 publications

References 26 publications

Three-frequency BDS precise point positioning ambiguity resolution based on raw observables

Three-frequency BDS precise point positioning ambiguity resolution based on raw observables

Performance Evaluation of Troposphere Estimated from Galileo-Only Multi-Frequency Observations

Impact of predicting real-time clock corrections during their outages on precise point positioning

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