Understanding long-term variations in GPS differential code biases

Xiang, Yan; Xu, Zhexin; Gao, Yang; Wang, Yu

doi:10.1007/s10291-020-01034-6

Cited by 12 publications

(6 citation statements)

References 27 publications

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“…Abnormal variations or significant discontinuities can be detected for the following satellites: G060 on DOY 161, C204 on DOY 135, R731 on DOY 160, R735 on DOY 100 and E205 on DOY 272. Similar discontinuities have also been observed in DCB and OSB time series by previous studies [11,26], which attributed this phenomenon to flex power or the occurrence of satellite maneuvers or onboard equipment maintenance in the constellation. Thus, although the OSBs of most satellites can remain stable over long time periods, it is better not to directly use the OSBs estimated on previous days, since significant jumps may occur in the OSB values between two consecutive days.…”

Section: Characteristics Of the Multi-gnss Satellite Osbssupporting

confidence: 84%

Estimation and Analysis of the Observable-Specific Code Biases Estimated Using Multi-GNSS Observations and Global Ionospheric Maps

Li¹,

Yuan²

2021

Remote Sensing

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Observable-specific bias (OSB) parameterization allows observation biases belonging to various signal types to be flexibly addressed in the estimation of ionosphere and global navigation satellite system (GNSS) clock products. In this contribution, multi-GNSS OSBs are generated by two different methods. With regard to the first method, geometry-free (GF) linear combinations of the pseudorange and carrier-phase observations of a global multi-GNSS receiver network are formed for the extraction of OSB observables, and global ionospheric maps (GIMs) are employed to correct ionospheric path delays. Concerning the second method, satellite and receiver OSBs are converted directly from external differential code bias (DCB) products. Two assumptions are employed in the two methods to distinguish satellite- and receiver-specific OSB parameters. The first assumption is a zero-mean condition for each satellite OSB type and GNSS signal. The second assumption involves ionosphere-free (IF) linear combination signal constraints for satellites and receivers between two signals, which are compatible with the International GNSS Service (IGS) clock product. Agreement between the multi-GNSS satellite OSBs estimated by the two methods and those from the Chinese Academy of Sciences (CAS) is shown at levels of 0.15 ns and 0.1 ns, respectively. The results from observations spanning 6 months show that the multi-GNSS OSB estimates for signals in the same frequency bands may have very similar code bias characteristics, and the receiver OSB estimates present larger standard deviations (STDs) than the satellite OSB estimates. Additionally, the variations in the receiver OSB estimates are shown to be related to the types of receivers and antennas and the firmware version. The results also indicate that the root mean square (RMS) of the differences between the OSBs estimated based on the CAS- and German Aerospace Center (DLR)-provided DCB products are 0.32 ns for the global positioning system (GPS), 0.45 ns for the BeiDou navigation satellite system (BDS), 0.39 ns for GLONASS and 0.22 ns for Galileo.

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Section: Characteristics Of the Multi-gnss Satellite Osbssupporting

confidence: 84%

Estimation and Analysis of the Observable-Specific Code Biases Estimated Using Multi-GNSS Observations and Global Ionospheric Maps

Li¹,

Yuan²

2021

Remote Sensing

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“…Apart from this specific case, the sub-daily variations of the User GGTO seem to be driven by the broadcast realization of GPST. The overall performance of broadcast GPST is limited by the accuracy of the broadcast ephemeris, as well as a possible impact of flex power that has been intensively used in recent years (Esenbuga and Hauschild 2020; Xiang et al 2020). The broadcast realization of GST appears to be more stable, confirming that the better quality of the Galileo broadcast ephemerides (Montenbruck et al 2018) benefits the system time access as well.…”

Section: Gnss-to-gnss Time Offsetsmentioning

confidence: 99%

UTC and GNSS system time access using PPP with broadcast ephemerides

et al. 2022

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The application of precise point positioning with broadcast ephemerides (PPP-BCE) is discussed as an alternative to the established all-in-view technique for multi-GNSS time transfer. It combines the use of broadcast ephemerides with low-noise carrier-phase observations for accessing GNSS system time scales and Coordinated Universal Time (UTC) with improved precision, and can be employed on stationary as well as mobile receivers in offline or real-time analyses. Using calibrated timing receivers, the method is shown to provide estimates of the GNSS-to-GNSS time offsets (XYTOs) with an accuracy at the 2 ns level. In the absence of prior calibrations, 0.5 ns consistency across different stations is achieved for GPS, Galileo, and BeiDou-3 after adjustment of systematic biases in comparison with calibrated reference stations or broadcast XYTO values. Furthermore, access to GNSS-specific UTC realizations can be obtained through predictions of the UTC offset from GNSS system time as provided in the broadcast ephemerides of individual constellations. The overall quality of the PPP-BCE-derived receiver clock offsets from UTC is assessed using calibrated receivers at various timing laboratories along with BIPM-provided UTC-UTC(k) measurements. Over the 1.5 years covered in the study, an accuracy of 1.8 ns for GPS and 2.5 ns for Galileo is demonstrated. For BeiDou, a slightly worse accuracy of 3 ns is obtained for a single timing laboratory over 9 months.

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“…Several previous studies have considered distinct frequencies, stations, satellite missions, and chipping rates to analyze the differential code bias (DCB). All of them have observed DCB values in the level of nanoseconds (e.g., [67], [68] and [69]), so our simulations also assume the magnitude of the absolute bias as nanoseconds. The developed model primarily focuses on simulating the inter-frequency biases, specifically assuming satellites from the same mission and utilizing a single modulation type.…”

Section: Gnss Payloadmentioning

confidence: 99%

Simulations of Dedicated LEO-PNT Systems for Precise Point Positioning: Methodology, Parameter Analysis, and Accuracy Evaluation

Prol,

Bhuiyan,

Kaasalainen

et al. 2024

IEEE Trans. Aerosp. Electron. Syst.

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Low Earth orbit (LEO) satellites provide the potential to overcome the current limitations in global navigation satellite systems (GNSS) due to the increased satellite velocity and signal reception power. As the whole LEO segment grows, preliminary studies and simulations have been conducted in the most recent years to identify how to develop a LEO-PNT system and add value to GNSS. To promote the development of LEO-PNT,

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Understanding long-term variations in GPS differential code biases

Cited by 12 publications

References 27 publications

Estimation and Analysis of the Observable-Specific Code Biases Estimated Using Multi-GNSS Observations and Global Ionospheric Maps

Estimation and Analysis of the Observable-Specific Code Biases Estimated Using Multi-GNSS Observations and Global Ionospheric Maps

UTC and GNSS system time access using PPP with broadcast ephemerides

Simulations of Dedicated LEO-PNT Systems for Precise Point Positioning: Methodology, Parameter Analysis, and Accuracy Evaluation

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