Research on a method of real-time combination of precise GPS clock corrections

Chen, Liang; Song, Weiwei; Yi, Wu; Shi, Chuang; Lou, Yidong; Guo, Hailin

doi:10.1007/s10291-016-0515-3

Cited by 18 publications

(10 citation statements)

References 7 publications

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“…an Analysis Centre (AC) Reference time offset (a bias). Similar clock jumps were observed by Mervart and Weber (2011) and Chen et al (2017). This offset is due to that the clock products are generated at the contributing ACs (currently eight ACs) using their inherent time scales, and the final RTS product is referenced to one of the ACs.…”

Section: Prediction Model Of the Clock Correctionssupporting

confidence: 76%

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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Section: Prediction Model Of the Clock Correctionssupporting

confidence: 76%

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

El‐Mowafy

2017

Survey Review

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“…It has been confirmed that if the accuracy of O a is better than 10 À6 s in (3), then the effect of O a can be totally absorbed by the receiver clock bias in PPP, having no effect on the PPP accuracy. Chen et al (2016) proved that O s a only impacts pseudorange observations while having no effect on phase observations, thereby having an effect only on the convergence time in PPP; C s determines the PPP accuracy. Therefore, the precision of O s a and C s indicate the performance of satellite clock offset products.…”

Section: Real-time Satellite Clock Offset Biasesmentioning

confidence: 98%

“…The real-time clock correction suffers from data outages and abnormalities due to many reasons (Chen et al 2016). The abnormal clock consists of gross errors, outages, and initial clock bias.…”

Section: Preprocessing Strategymentioning

confidence: 99%

Method for evaluating real-time GNSS satellite clock offset products

Yao

et al. 2017

GPS Solut

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Real-time satellite clock offset products are frequently utilized in navigation and positioning service fields. The precision of such products is a key issue for their application. The evaluation methods existed for satellite clock offset products are mostly based on post-processed satellite clock offset solutions, which will encounter problems in real-time product evaluation, especially for realtime satellite clock offset products estimated from data with regional stations only. We propose an improved evaluation method for global navigation satellite system (GNSS) satellite clock offset products. In the proposed method, we use all-satellite reference method instead of single-satellite reference method to eliminate the timescale in satellite clock offset products. Moreover, a preprocessing step is suggested to detect gross errors and initial clock bias before evaluating the precision of the satellite clock offsets. We conduct two examples to verify our method, and the experimental results show that the proposed method is more reasonable in assessing the GNSS satellite clock offset precision, and it also provides a reliable approach to analyzing the estimated satellite clock offset in both real-time and post-processed, or globally and regionally.

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“…Besides, an initial clock is introduced to convert the epoch-differenced clock offsets into the un-differenced ones in the mixed-differenced method. Overall, the traditional model of the clock product can be described as [8,31] C s…”

Section: Model Of Real-time Bds Clock Productmentioning

confidence: 99%

An Improved Multi-Satellite Method for Evaluating Real-Time BDS Satellite Clock Offset Products

et al. 2020

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Two methods are widely used for evaluating the precision of satellite clock products, namely the single-satellite method (SSM) and the multi-satellite method (MSM). In the satellite clock product evaluation, an important issue is how to eliminate the timescale difference. The SSM selects a reference satellite to eliminate the timescale difference by between-satellite differencing, but its evaluation results are susceptible to the gross errors in the referenced satellite clock offsets. In the MSM, the timescale difference is first estimated and then removed. Unlike the GPS, the BeiDou Navigation Satellite System (BDS) consists of three types of satellites, namely geosynchronous earth orbit (GEO), inclined geosynchronous orbit (IGSO), and medium earth orbit (MEO) satellites. The three types of satellites have uneven orbital accuracy. In the generation of satellite clock products, the orbital errors are partly assimilated into the clock offsets. If neglecting the orbital accuracy difference of the three types of BeiDou satellites, the MSM will obtain biased estimates of the timescale difference and finally affect the clock product evaluation. In this study, an improved multi-satellite method (IMSM) is proposed for evaluating the real-time BDS clock products by removing the assimilated orbital errors of the three types of BDS satellites when estimating the timescale difference. Three real-time BDS clock products disseminated by three different International GNSS Service (IGS) analysis centers, namely CLK16, CLK20, and CLK93, over a period of two months are used to validate this method. The results indicate that the assimilated orbital errors have a significant impact on the estimation of the timescale difference. Subsequently, the IMSM is compared with the SSM in which the referenced satellite is rigorously chosen, and their RMS difference is only 0.08 ns, which suggests that the evaluation results obtained by the IMSM are accurate. Compared with the traditional MSM, the IMSM improves the RMS by 0.16, 0.11, and 0.07 ns for CLK16, CLK20, and CLK93, respectively. Finally, three real-time BDS clock products are evaluated using the proposed method, and results reveal a significant precision difference among them.

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Research on a method of real-time combination of precise GPS clock corrections

Cited by 18 publications

References 7 publications

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

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

Method for evaluating real-time GNSS satellite clock offset products

An Improved Multi-Satellite Method for Evaluating Real-Time BDS Satellite Clock Offset Products

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