Galileo PPP rapid ambiguity resolution with five-frequency observations

Li, Xingxing; Liu, Gege; Zhou, Feng; Feng, Guolong; Yuan, Yongqiang; Zhang, Keke

doi:10.1007/s10291-019-0930-3

Cited by 66 publications

(30 citation statements)

References 26 publications

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“…In the present contribution, we make use of the uncombined GPS dual-frequency model to determine network-derived estimable satellite phase biases and predicted ionospheric corrections for single-receiver fast IAR. Although multi-frequency and multi-GNSS PPP-RTK have proven to bring an improvement in the convergence time [18,19], the focus has been given mostly to the ionosphere-float models. In this study we focus solely on the ionosphere-weighted model.…”

Section: Introductionmentioning

confidence: 99%

Real-Time PPP-RTK Performance Analysis Using Ionospheric Corrections from Multi-Scale Network Configurations

Psychas

Verhagen

2020

Sensors

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The long convergence time required to achieve high-precision position solutions with integer ambiguity resolution-enabled precise point positioning (PPP-RTK) is driven by the presence of ionospheric delays. When precise real-time ionospheric information is available and properly applied, it can strengthen the underlying model and substantially reduce the time required to achieve centimeter-level accuracy. In this study, we present and analyze the real-time PPP-RTK user performance using ionospheric corrections from multi-scale regional networks during a day with medium ionospheric disturbance. It is the goal of this contribution to measure the impact the network dimension has on the ambiguity-resolved user position through the predicted ionospheric corrections. The user-specific undifferenced ionospheric corrections are computed at the network side, along with the satellite phase biases needed for single-receiver ambiguity resolution, using the best linear unbiased predictor. Such corrections necessitate the parameterization of an estimable user receiver code bias, on which emphasis is given in this study. To this end, we process GPS dual-frequency data from four four-station evenly distributed CORS networks in the United States with varying station spacings in order to evaluate if and to what extent the ionospheric corrections from multi-scale networks can improve the user convergence times. Based on a large number of samples, our experimental results showed that sub-10 cm horizontal accuracy can be achieved almost instantaneously in the ionosphere-weighted partially-ambiguity-fixed kinematic PPP-RTK solutions based on corrections from a network with 68 km spacing. Most of the solutions (90%) were shown to require less than 6.0 min, compared to the ionosphere-float PPP solutions that needed 68.5 min. In case of sparser networks with 115, 174 and 237 km spacing, 50% of the horizontal positioning errors are shown to become less than one decimeter after 1.5, 4.0 and 7.0 min, respectively, while 90% of them require 10.5, 16.5 and 20.0 min. We also numerically demonstrated that the user’s convergence times bear a linear relationship with the network density and get shorter as the density increases, for both full and partial ambiguity resolution.

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Section: Introductionmentioning

confidence: 99%

Real-Time PPP-RTK Performance Analysis Using Ionospheric Corrections from Multi-Scale Network Configurations

Psychas

Verhagen

2020

Sensors

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“…where, (20), (21) as shown at bottom of this page. σ ϕ = 0.01 cycle and σ P = 0.03 m are assumed as the carrier phase and pseudo-range noises, respectively, and the observations are independent of each other.…”

Section: Geometry-free Carrier Phase Combinationmentioning

confidence: 99%

“…In terms of the linear combinations of triple frequency carrier phase, Richert and El-Sheimy [19] introduced the concept of optimal linear combinations of carrier phase measurements; it was established that the choice of an optimal combination was determined by the baseline length, the physical error environment, as well as the requirements of the given mission. For the five-frequency Galileo PPP, Li et al [20] suggested that the convergence time of quad-and five-frequency PPP Ambiguity solution (AR) was improved compared with that of triple-frequency PPP AR. The multi-frequency signals are capable of enhancing the accuracy and reliability of CDR [21]- [24].…”

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confidence: 99%

A New Cycle Slip Detection and Repair Method for Galileo Four-Frequency Observations

et al. 2020

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Galileo four-frequency cycle slip detection and repair (CDR) is susceptible to the noise of pseudo-range observations. In this study, the Galileo four-frequency carrier phase smoothed pseudo-range (CPSP) assisted CDR method was proposed. Such method was conducted in three steps in sequence. First, the four linear independent combinations of the Galileo four-frequency observation were taken for CDR. Second, the non-divergent Hatch filter was employed to carry out the pseudo-range observation smoothly. Third, the true cycle slip was determined by rounding the float value using the least square method. To take the optimal combination of the CDR and verify the feasibility of the proposed method, the Galileo observations with satellites in different types were performed. According to the experimental results, (1) the four linear independent combinations of the geometry-free carrier phase combination (0, 1, 0, −1), (1, 1, −1, −1), (1, 2, −2, −1) and geometry-free and ionosphere-free combination (0, 0, 1, −1) were adopted for the cycle slip detection; (2) The success rate of cycle slip repair reached over 99.99% after four-frequency CPSP processing. With the CPSP assisted CDR method, the differences of the root mean square (RMS) between float and true values were down-regulated by 79.61%, 70.03%, 66.25% and 72.75%, respectively. (3) The differences of the root mean square (RMS) between float and true values were down-regulated by 13.62%, 10.67%, 10.67% and 10.67% after smoothing, respectively. In summary, the Galileo four-frequency CDR was effectively performed by the proposed method in active ionospheric area. INDEX TERMS Carrier-phase smoothed pseudo-range, cycle slip detection and repair, Galileo, fourfrequency, observation noise. I. INTRODUCTION Carrier phase observations are applied to high-precision Global Navigation Satellite System (GNSS) positioning, which covers real-time kinematic (RTK) and precise point positioning (PPP). Nevertheless, carrier phase observations are likely to be adversely affected by cycle slips that are attributed to obstructions of the satellite signal, multipath and high receiver dynamics, etc. Thus, the cycle slip detection and repair (CDR) is critical to high-precision GNSS positioning [1]-[4].

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“…Moreover, the results indicate that the fractional parts of extra-wide-lane ambiguities for all Galileo satellites are all zero, which may be associated with the characteristic of the AltBOC signal. Li et al [20] analyzed the multi-frequency PPP ambiguity resolution method based on the Galileo five-frequency observations. While the use of more frequencies contributes in a minor way to the TTFF, decimeter-level positioning accuracy can be achieved within 0.5 min by utilizing triple-/quad-/five-frequency PPP wide-lane ambiguity resolution.…”

Section: Introductionmentioning

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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Galileo PPP rapid ambiguity resolution with five-frequency observations

Cited by 66 publications

References 26 publications

Real-Time PPP-RTK Performance Analysis Using Ionospheric Corrections from Multi-Scale Network Configurations

Real-Time PPP-RTK Performance Analysis Using Ionospheric Corrections from Multi-Scale Network Configurations

A New Cycle Slip Detection and Repair Method for Galileo Four-Frequency Observations

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

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