Global Ionospheric Modelling using Multi-GNSS: BeiDou, Galileo, GLONASS and GPS

Ren, Xiaodong; Zhang, Xiaohong; Xie, Weiliang; Zhang, Keke; Yuan, Yongqiang; Li, Xingxing

doi:10.1038/srep33499

Cited by 83 publications

(45 citation statements)

References 24 publications

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“…Both BDGIM and NTCM-BC utilize the mapping function M F for converting VTEC to STEC. The expression of M F is given by: (15) where Re denotes the earth's mean radius. H ion represents the height of the thin shell of the ionosphere, and it is set to 400 km.…”

Section: Ntcm-bcmentioning

confidence: 99%

Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

et al. 2020

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For single-frequency Global Navigation Satellite Systems (GNSSs) users, ionospheric delay is the main error source affecting the accuracy of positioning. Applying a broadcast ionospheric correction model to mitigate the ionospheric delay is essential for meter-to-decimeter-level accuracy positioning. To provide support for real-time single-frequency operations, particularly in the China area, we assessed the performance of three broadcast ionospheric correction models, namely, the Neustrelitz total electron content (TEC) broadcast model (NTCM-BC), the BeiDou global broadcast ionospheric delay correction model (BDGIM), and the Klobuchar model. In this study, the broadcast coefficients of Klobuchar and BDGIM are obtained from the navigation data files directly. Two sets of coefficients of NTCM-BC for China and global areas are estimated. The slant total electron contents (STEC) data from more than 80 validation stations and the final vertical TEC (VTEC) data of the Center for Orbit Determination in Europe (CODE) are used as independent benchmarks for comparison. Compared to GPS STEC during the period of Day of Year (DOY) 101~199, 2019, the ionospheric correction ratio of NTCM-BC, BDGIM, and Klobuchar are 79.4%, 64.9%, and 57.7% in China, respectively. For the global area, the root-mean-square (RMS) errors of these three models are 3.67 TECU (1 TECU = 10 16 electrons/m 2 ), 5.48 TECU, and 8.92 TECU, respectively. Compared to CODE VTEC in the same period, NTCM-BC, BDGIM, and Klobuchar can correct 72.6%, 69.8%, and 61.7% of ionospheric delay, respectively. Hence, NTCM-BC is recommended for use as the broadcast ionospheric model for the new-generation BeiDou satellite navigation system (BDS) and its satellite-based augmentation system. broadcasting in the navigation message. The Klobuchar model is a third-order polynomial function depending on local time (LT) and geomagnetic latitude. It is generally assumed that the Klobuchar model can reduce the ionospheric range error by 50% [1]. Because of its simplicity, it is widely used in the GNSSs single-frequency mass market. Meanwhile, the European Galileo system uses a three-dimension model known as NeQuick, which is developed by the International Center for Theoretical Physics (ICTP) at the Trieste and the University of Graz [3][4][5]. The Galileo single-frequency operations can use three correction coefficients, which are transmitted as a part of the Galileo navigation message to compute the ionospheric electron density along the ground-to-satellite propagation path. As for the BeiDou satellite navigation system (BDS), the regional BeiDou (BDS-2) broadcasts eight parameters and uses a slightly modified Klobuchar model (BDSKlobuchar) to calculate ionospheric delay. It is almost the same as the Klobuchar model except for the reference frame and the update frequency of parameters. BDS has launched the new generation of satellites (BDS-3) since 2017. The new satellites apply new navigation signals and technologies to provide global service. Moreover, a global broadcast ionosp...

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Section: Ntcm-bcmentioning

confidence: 99%

Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

et al. 2020

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“…This commonly used methodology reduces the observations noise, from code to phase levels, and avoids the estimation of phase ambiguities, but it could also introduce some systematic errors (see, e.g., Ciraolo et al, 2007;Spits, 2012). In addition, each GF observation is weighted according to three factors: the instantaneous satellite elevation, the amount of observations employed during the carrier-to-code leveling (i.e., the length of each phase-continuous interval) and the corresponding navigational system (GPS, 7 GLONASS, Galileo or BeiDou, see Ren et al, 2016). Then, the full set of GF observations is represented as…”

Section: Gnssmentioning

confidence: 99%

Near-real-time VTEC maps: New contribution for Latin America Space Weather

Mendoza

Meza

Paz

2020

Advances in Space Research

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The development of regional services able to provide ionospheric vertical total electron content (VTEC) maps and ionospheric indexes with a high spatial resolution, and in near-real-time, are of great importance for both civilian applications and the research community. We provide here the methodologies, and an assessment, of such a system. It relies on the public Global Navigational Satellite Systems (GNSS) infrastructure in South America, incorporates data from multiple constellations (currently GPS, GLONASS, Galileo and BeiDou), employs multiple frequencies, and produces continental wide VTEC maps with a latency of just a few minutes. To assess the ability of our system to model the ionospheric behavior we performed a yearround intercomparison between our near-real-time regional VTEC maps, and VTEC maps of verified quality produced by several referent analysis centers, resulting in mean biases lower than 1 TEC units (TECU). Also, the evaluation of our products against direct and independent GNSS-based slant TEC measurements shows RMS values better than 1 TECU. In turn, ionospheric weather W-index maps were generated, for calm and disturbed geomagnetic scenarios, solely employing our quality verified VTEC maps. The spatial representation of these W-index maps reflects the state of the ionosphere, with a resolution of 0.5 × 0.5 degrees. Finally, we conclude that our products, computed every 15 minutes, do provide an excellent spatial representation of the regional TEC, and are able to provide the bases for the possible computation of ionospheric W-index maps, also in near-real-time.

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“…The B1C signal centered at 1,575.42 MHz is transmitted in TMBOC(6,1) modulation, and is compatible with GPS L1 signal and Galileo E1 signal. The B2a signal with a center frequency of 1176.45 MHz is modulated using BPSK(10), AltBOC (15,10) or TD-AltBOC(15,10) modulation, and is compatible with GPS L5 signal and Galileo E5a signal. The AltBOC (15,10) or TD-AltBOC(15,10) modulated B2b signal matches the Galileo E5b signal.…”

Section: Data Acquisitionmentioning

confidence: 99%

“…The B2a signal with a center frequency of 1176.45 MHz is modulated using BPSK(10), AltBOC (15,10) or TD-AltBOC(15,10) modulation, and is compatible with GPS L5 signal and Galileo E5a signal. The AltBOC (15,10) or TD-AltBOC(15,10) modulated B2b signal matches the Galileo E5b signal. It should be noted that the B2 signal of BDS-2 satellites and the B2b signal of BDS-3 satellites share the same frequency, but their modulation types are different.…”

Section: Data Acquisitionmentioning

confidence: 99%

Considering Inter-Frequency Clock Bias for BDS Triple-Frequency Precise Point Positioning

Pan

Zhang

et al. 2017

Remote Sensing

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Abstract:The joint use of multi-frequency signals brings new prospects for precise positioning and has become a trend in Global Navigation Satellite System (GNSS) development. However, a new type of inter-frequency clock bias (IFCB), namely the difference between satellite clocks computed with different ionospheric-free carrier phase combinations, was noticed. Consequently, the B1/B3 precise point positioning (PPP) cannot directly use the current B1/B2 clock products. Datasets from 35 globally distributed stations are employed to investigate the IFCB. For new generation BeiDou Navigation Satellite System (BDS) satellites, namely BDS-3 satellites, the IFCB between B1/B2a and B1/B3 satellite clocks, between B1/B2b and B1/B3 satellite clocks, between B1C/B2a and B1C/B3 satellite clocks, and between B1C/B2b and B1C/B3 satellite clocks is analyzed, and no significant IFCB variations can be observed. The IFCB between B1/B2 and B1/B3 satellite clocks for BDS-2 satellites varies with time, and the IFCB variations are generally confined to peak amplitudes of about 5 cm. The IFCB of BDS-2 satellites exhibits periodic signal, and the accuracy of prediction for IFCB, namely the root mean square (RMS) statistic of the difference between predicted and estimated IFCB values, is 1.2 cm. A triple-frequency PPP model with consideration of IFCB is developed. Compared with B1/B2-based PPP, the positioning accuracy of triple-frequency PPP with BDS-2 satellites can be improved by 12%, 25% and 10% in east, north and vertical directions, respectively.

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Global Ionospheric Modelling using Multi-GNSS: BeiDou, Galileo, GLONASS and GPS

Cited by 83 publications

References 24 publications

Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

Near-real-time VTEC maps: New contribution for Latin America Space Weather

Considering Inter-Frequency Clock Bias for BDS Triple-Frequency Precise Point Positioning

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