Characteristics of Onefold Clocks of GPS, Galileo, BeiDou and GLONASS Systems

Ai, Qingsong; Maciuk, Kamil; Lewińska, Paulina; Borowski, Łukasz

doi:10.3390/s21072396

Cited by 15 publications

(7 citation statements)

References 22 publications

(31 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After outlier detection, if a data point was outside of the selected MAD width criterion, it was removed from further analysis. Figure 3 shows a sample raw frequency data of a clock correction file with a relatively big (~2 ps) magnitude, which is eliminated using the MAD method [29].…”

Section: Resultsmentioning

confidence: 99%

A Study of Outliers in GNSS Clock Products

Maciuk,

Varna,

Krzykowska-Piotrowska

2024

Sensors

Self Cite

View full text Add to dashboard Cite

Time is an extremely important element in the field of GNSS positioning. In precise positioning with a single-centimetre accuracy, satellite clock corrections are used. In this article, the longest available data set of satellite clock corrections of four GNSS systems from 2014 to 2021 was analysed. This study covers the determination of the quality (outliers number and magnitude), availability, stability, and determination of the specificity and nature of the clock correction for each satellite system. One problem with the two newest satellite systems (Galileo and BeiDou) is the lack of availability of satellite signals in the early years of the analysis. These data were available only in the later years of the period covered by the analysis, as most of the satellites have only been in orbit since 2018–2019. Interestingly, the percentage of outlying observations was highest in Galileo and lowest in BeiDou. Phase and frequency plots showed a significant number of outlying observations. On the other hand, after eliminating outlying observations, each system showed a characteristic graph waveform. The most consistent and stable satellite clock corrections are provided by the GPS and GLONASS systems. The main problems discussed in this paper are the determination of the number and magnitude of outliers in clock products of four GNSS systems (GPS, GLONASS, Galileo, Beidou) and the study on the long-term stability of GNSS clocks analysis, which covers the years 2014–2021.

show abstract

Section: Resultsmentioning

confidence: 99%

A Study of Outliers in GNSS Clock Products

Maciuk,

Varna,

Krzykowska-Piotrowska

2024

Sensors

Self Cite

View full text Add to dashboard Cite

show abstract

“…Comparing the ADEV, the performance of COMPASS clocks is comparable to late GLONASS clocks, older GPS clocks, and the Galileo RAFS, but Rb clock of GPS Block IIF has the best performance. Qingsong Ai et al [23] note that GPS block IIF RAFS clocks are more stable than those of block IIR, and GLONASS shows a good clock consistency by having very small frequency drift, which can be ascribed to the equipment of the same type of Cs atomic clock. Comprehensively, clock stability of Galileo and GPS is better than GLONASS and BeiDou [23].…”

Section: Relative Performance Beidou-2 and Contemporary Gnsssmentioning

confidence: 99%

“…Qingsong Ai et al [23] note that GPS block IIF RAFS clocks are more stable than those of block IIR, and GLONASS shows a good clock consistency by having very small frequency drift, which can be ascribed to the equipment of the same type of Cs atomic clock. Comprehensively, clock stability of Galileo and GPS is better than GLONASS and BeiDou [23]. Comparing the major noise affecting clocks onboard different GNSSs, the GPS and BDS clocks were more influenced by the Random Walk Frequency Modulation (RWFM), Flicker Frequency Modulation (FFM), and White Frequency Modulation (WFM) noise while GLONASS clocks, due to Cs clock characteristics, are mainly affected by WFM [23].…”

Section: Relative Performance Beidou-2 and Contemporary Gnsssmentioning

confidence: 99%

“…Comprehensively, clock stability of Galileo and GPS is better than GLONASS and BeiDou [23]. Comparing the major noise affecting clocks onboard different GNSSs, the GPS and BDS clocks were more influenced by the Random Walk Frequency Modulation (RWFM), Flicker Frequency Modulation (FFM), and White Frequency Modulation (WFM) noise while GLONASS clocks, due to Cs clock characteristics, are mainly affected by WFM [23]. These results derive solely from the 3 randomly selected satellites from each GNSS, which exclusively uses BeiDou-2 satellites C09, C10, and C12 to compare with GPS block IIR and IIF, Galileo FOC, and GLONASS satellites [3,23].…”

Section: Relative Performance Beidou-2 and Contemporary Gnsssmentioning

confidence: 99%

See 1 more Smart Citation

Status quo and improvements of timekeeping in GNSSs

Liu

2023

TNS

View full text Add to dashboard Cite

A time offset of 1 microsecond could lead to 300-meter positioning offset for a global navigational satellite system (GNSS). Therefore, appropriately evaluating and improving the clock performance onboard GNSS satellites are critical. The research methods and conclusions of papers written in distinct periods about their contemporary satellites clocks are chronologically synthesized. The satellites clocks among the same and different GNSSs are compared, with the time primarily centered around the launching and development of BeiDou-2 and BeiDou-3. It is found that passive hydrogen maser (PHM) and rubidium atomic frequency standard (RAFS) have a better performance than cesium (Cs) clocks, and PHM are among the best clock onboard satellites so more attention may be given to its development. Two major factors affecting timekeeping precision are the selection of clock manufacturers and clock types. The European manufacturing technique is pioneering, but the RAFS and PHM independently developed by China in recent years indicate a good performance. To improve navigation service, an accurate evaluation of satellites performance should be conducted, and the results can be used to assign the weight of satellite differently in computing navigation information.

show abstract

“…Research into the performance of GPS satellite clocks has considerably improved in recent years [12,[17][18][19]. Performance evaluation and analysis of BDS, Galileo and GLONASS satellite atomic clocks has been carried out in succession [20][21][22]. With the rapid advancement of the BDS, the performance of BDS-2 satellite atomic clocks has been studied widely over the past decade [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Comparison and Assessment on Long-Term Performance of BDS-2/BDS-3 Satellite Atomic Clocks

Chen

Zhao

et al. 2021

Meas. Sci. Technol.

View full text Add to dashboard Cite

Recently, the performance of the new-generation BeiDou Navigation Satellite System (BDS) satellite clocks has attracted considerable attention. There are two types of BDS clocks developed in China—namely, the new rubidium (Rb-II) and passive hydrogen maser (PHM)—and these can affect positioning, navigation and timing (PNT) services. In this paper, to comprehensively evaluate and analyze the performance of BDS satellite atomic clocks, the physical characteristics are exhibited, including phase, frequency, frequency drift and noise. The physical characteristics are applied to detect the switching of satellite clocks. The frequency stability of atomic clocks is assessed by overlapping Allan deviation (ADEV) and overlapping Hadamard deviation (HDEV). The periodic characteristics of satellite clock bias data are studied through spectrum analysis. Based on 550 day precision satellite clock bias data provided by Wuhan University, China, experiments were performed, focusing on the performance of the Rb-II and PHM clocks installed on BDS-3. Some valuable conclusions are obtained: (a) the BDS-3 satellite clocks perform better than BDS-2. The root mean square value of the frequency drift of BDS-3 satellite clocks is enhanced by 41% compared to BDS-2. The noise of BDS-3 is 0.216 ns, which is 55% better than BDS-2. (b) The frequency stability of BDS-2 satellite clocks is worse than that of BDS-3. The mean daily stability of BDS-2 and BDS-3 satellite clocks by ADEV is 5.29 × 10−14 and 5.36 × 10−14, respectively, while that with HDEV is 2.35 × 10−14 and 0.70 × 10−14. For PHM clocks, the stability at 10 000 s with ADEV and HDEV is 2.29 × 10−14 and 2.25 × 10−14, respectively, while the daily stability is 0.77 × 10 −14 and 0.67 × 10−14, respectively. (c) BDS geostationary orbit (GEO) and inclined GEO satellite atomic clocks have multiple significant periodic terms while the medium earth orbit satellite clocks only own one or two, which are related to the corresponding satellite orbital periods.

show abstract

Characteristics of Onefold Clocks of GPS, Galileo, BeiDou and GLONASS Systems

Cited by 15 publications

References 22 publications

A Study of Outliers in GNSS Clock Products

A Study of Outliers in GNSS Clock Products

Status quo and improvements of timekeeping in GNSSs

Comparison and Assessment on Long-Term Performance of BDS-2/BDS-3 Satellite Atomic Clocks

Contact Info

Product

Resources

About