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Author

Xiaomin Luo

Bio: Xiaomin Luo is an academic researcher. The author has contributed to research in topics: Computer science & Ionosphere. The author has an hindex of 2, co-authored 11 publications receiving 11 citations.

Papers
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DOI
01 Jan 2022
TL;DR: In this article , the authors proposed a geometry-free cycle slip threshold model based on ionospheric disturbance index rate of total electron content index to reduce the false detection rate of cycle slip in GNSS precise point positioning during strong storm periods, thus improving the accuracy and reliability of GNSS PPP.
Abstract: Geomagnetic storm can affect the performance of Global Navigation Satellite System (GNSS) precise positioning services. To mitigate the adverse effects of strong geomagnetic storms, we propose to establish the geometry‐free (GF) cycle slip threshold model based on ionospheric disturbance index rate of total electron content index to reduce the false detection rate of cycle slip in GNSS precise point positioning (PPP) during strong storm periods, thus improving the accuracy and reliability of GNSS PPP. The performance of our proposed model is validated by using 171 International GNSS Service (IGS) tracking stations data on 8 September 2017. The analysis indicates that compared with conventional PPP scheme, the proposed model can improve the positioning accuracy by approximately 14.0% (36.8%) and 23.1% (51.5%) in the horizonal and vertical components for global (high latitudes) stations. Furthermore, the availability of our proposed model is also validated by PPP experiments using 379 IGS tracking stations data during another strong storm occurred on 26 August 2018.

5 citations

DOI
24 Jun 2022
TL;DR: In this paper , the rate of total electron content index (ROTI) parameter was incorporated into the EAS model to mitigate severe storm effects on GNSS PPP, which improved the PPP accuracy in 3D direction by approximately 12.9% to 14.7%.
Abstract: For global navigation satellite system (GNSS), ionospheric disturbances caused by the geomagnetic storm can reduce the accuracy and reliability of precision point positioning (PPP). At present, common stochastic models in GNSS PPP, such as the elevation angle stochastic (EAS) model or carrier‐to‐noise power‐density ratio ( C/N0 $C/{N}_{\mathit{0}}$ ) based SIGMA‐ ε $\varepsilon $ model, do not properly consider storm effects on GNSS measurements. To mitigate severe storm effects on GNSS PPP, this study further implements the rate of total electron content index (ROTI) parameter into the EAS model referred to as the EAS‐ROTI model. This model contains two operations. The first one is to adjust variance of GNSS measurements using ROTI observations on EAS model. The second one is to determine the ratio of the priori variance factor between pseudorange and carrier phase measurements during severe storm conditions. The performance of EAS‐ROTI model is verified by using a large number of international GNSS service stations datasets on 17 March and 23 June in 2015. Experimental results indicate that on a global scale, the EAS‐ROTI model improves the PPP accuracy in 3D direction by approximately 12.9%–14.7% compared with the EAS model, and by about 24.8%–45.9% compared with the SIGMA‐ ε $\varepsilon $ model.

2 citations

Journal ArticleDOI
TL;DR: In this paper , the authors extracted the signal-to-noise-ratio (SNR) data of CSES and calculated the standard deviation of normalized normalized SNR.
Abstract: Abstract. GNSS radio occultation (RO) plays an important role in ionospheric electron density inversion and sounding of sporadic E layers. As China's first electromagnetic satellite, China Seismo-Electromagnetic Satellite (CSES) has collected the RO data from both GPS and BDS-2 satellites since March 2018. In this study, we extracted the signal-to-noise ratio (SNR) data of CSES and calculated the standard deviation of normalized SNR. A new criterion is developed to determine the Es events, that is, when the mean value of the absolute value of the difference between the normalized SNR is greater than 3 times the standard deviation. The statistics show that sporadic E layers have strong seasonal variations with highest occurrence rates in summer season at middle latitudes. It is also found that the occurrence height of Es is mainly located at 90–110 km, and the period 14:00–20:00 LT is the high incidence period of Es. In addition, the geometric altitudes of a sporadic E layer detected in CSES radio occultation profiles and the virtual heights of a sporadic E layer obtained by the Wuhan Zuoling station (ZLT) ionosonde show three different space-time matching criteria. Our results reveal that there is a good agreement between both parameters which is reflected in the significant correlation.

2 citations

Journal ArticleDOI
TL;DR: Using the global navigation satellite system (GNSS) data from the Hong Kong region, the authors comprehensively investigated the ionospheric irregularities responses to strong geomagnetic storms over the past two solar cycles 2001-2020.
Abstract: Using the global navigation satellite system (GNSS) data from the Hong Kong region, this study comprehensively investigates the ionospheric irregularities responses to strong geomagnetic storms over the past two solar cycles 2001–2020. Based on the geomagnetic index Dst, a total of 64 strong storms are confirmed during 2001–2020. Statistical results indicate that for the total 64 strong storms, only 20 storms are considered to trigger irregular occurrences. When the occurrence local time (LT) of the minimum dDst (dDst $_{\mathrm {min}}$ ) is in 10:00–14:00 LT, no ionospheric irregularities occurred at nighttime although there is a total of 14 strong storms, while that of dDst min is in the nighttime of 18:00–21:00 LT, ionospheric irregularities are detected in ten out of 12 strong storms. For the two special storms on 19 April 2002 (dDst min occurred at 21:00 LT) and 23 May 2002 (dDst min occurred at 20:00 LT), they did not trigger the generation of ionospheric irregularities although their dDst min occurred in 18:00–21:00 LT. Based on vertical total electron content (VTEC) derived from global positioning system (GPS) measurements, it is found that the westward electric fields during two storms should play a vital role to inhibit the nighttime ionospheric irregularities (NIIs) occurrence. This study suggests that caution should be taken when the dDst min determined LT is used to decide the occurrence of nighttime irregularities.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: Different learning algorithms to approximate nonlinear space weather processes and forecast VTEC for 1 h and 24 h in the future for low-, mid- and high-latitude ionospheric grid points along the same longitude are investigated.
Abstract: Space weather describes varying conditions between the Sun and Earth that can degrade Global Navigation Satellite Systems (GNSS) operations. Thus, these effects should be precisely and timely corrected for accurate and reliable GNSS applications. That can be modeled with the Vertical Total Electron Content (VTEC) in the Earth’s ionosphere. This study investigates different learning algorithms to approximate nonlinear space weather processes and forecast VTEC for 1 h and 24 h in the future for low-, mid- and high-latitude ionospheric grid points along the same longitude. VTEC models are developed using learning algorithms of Decision Tree and ensemble learning of Random Forest, Adaptive Boosting (AdaBoost), and eXtreme Gradient Boosting (XGBoost). Furthermore, ensemble models are combined into a single meta-model Voting Regressor. Models were trained, optimized, and validated with the time series cross-validation technique. Moreover, the relative importance of input variables to the VTEC forecast is estimated. The results show that the developed models perform well in both quiet and storm conditions, where multi-tree ensemble learning outperforms the single Decision Tree. In particular, the meta-estimator Voting Regressor provides mostly the lowest RMSE and the highest correlation coefficients as it averages predictions from different well-performing models. Furthermore, expanding the input dataset with time derivatives, moving averages, and daily differences, as well as modifying data, such as differencing, enhances the learning of space weather features, especially over a longer forecast horizon.

14 citations

DOI
24 Jun 2022
TL;DR: In this paper , the rate of total electron content index (ROTI) parameter was incorporated into the EAS model to mitigate severe storm effects on GNSS PPP, which improved the PPP accuracy in 3D direction by approximately 12.9% to 14.7%.
Abstract: For global navigation satellite system (GNSS), ionospheric disturbances caused by the geomagnetic storm can reduce the accuracy and reliability of precision point positioning (PPP). At present, common stochastic models in GNSS PPP, such as the elevation angle stochastic (EAS) model or carrier‐to‐noise power‐density ratio ( C/N0 $C/{N}_{\mathit{0}}$ ) based SIGMA‐ ε $\varepsilon $ model, do not properly consider storm effects on GNSS measurements. To mitigate severe storm effects on GNSS PPP, this study further implements the rate of total electron content index (ROTI) parameter into the EAS model referred to as the EAS‐ROTI model. This model contains two operations. The first one is to adjust variance of GNSS measurements using ROTI observations on EAS model. The second one is to determine the ratio of the priori variance factor between pseudorange and carrier phase measurements during severe storm conditions. The performance of EAS‐ROTI model is verified by using a large number of international GNSS service stations datasets on 17 March and 23 June in 2015. Experimental results indicate that on a global scale, the EAS‐ROTI model improves the PPP accuracy in 3D direction by approximately 12.9%–14.7% compared with the EAS model, and by about 24.8%–45.9% compared with the SIGMA‐ ε $\varepsilon $ model.

2 citations

Journal ArticleDOI
TL;DR: An analysis and experiment of the design and evaluation of PPP-RTK through Q channel based on the existing P PP-B2b I channel signal suggested that the positioning accuracy of GPS+BDS+Galileo PPP -RTK under 95% quantile is roughly the same.
Abstract: Precise point positioning (PPP) is one of the seven planning public services of the new generation global Beidou Navigation Satellite System (BDS), i.e. BDS-3. Up to now, the PPP service signal has already been broadcast through I channel of PPP-B2b to support decimeter level positioning within 30 min for users over China and the surrounding areas for free. Concerning the potential application of PPP real-time kinematic (PPP-RTK) in the BDS positioning service development, this paper carried out analysis and experiment of the design and evaluation of PPP-RTK through Q channel based on the existing PPP-B2b I channel signal. First, we presented the algorithm of PPP-RTK based on the undifferenced and uncombined model. Then, the format and broadcast strategy of phase delay and atmospheric delay products were discussed in detail. Finally, based on the simulation data, we analyzed the performance of PPP-RTK with different broadcast bandwidths. The results suggested that the positioning accuracy of GPS + BDS + Galileo PPP-RTK under 95% quantile were 2.3 cm and 3.3 cm in horizontal and vertical, respectively. In order to evaluate the BDS PPP-RTK service, we set the convergence thresholds as 6 cm in horizontal and 12 cm in vertical, which is given by Centimeter Level Augmentation Service of Japanese Quasi-Zenith Satellite System, and the time to converge to such thresholds were 0.5 min and 1.0 min in horizontal and vertical, respectively. Finally, the experiment considering ‘correction latency’ suggested that there was only a litter effect on the convergence speed, the positioning accuracy after convergence is roughly the same.

2 citations

Journal ArticleDOI
TL;DR: In this article , the authors applied the height-time-intensity (HTI) technique along with Spectrum (Lomb periodogram) analysis to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs) traces over Moscow, which are characterized by a 12-h periodicity prevailing throughout the year.
Abstract: Abstract Nine years of ionograms from a higher mid-latitude ionospheric station (Moscow) are analyzed, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs). Es and IDL traces are observed over Moscow, which are characterized by a 12-h periodicity prevailing throughout the year. Shorter periodicities in IDL and Es occurrence are also observed. A 6-h periodicity in Es and IDL dominates during November and December, while an 8-h periodicity is found mainly from October to February for IDL and in July for Es. These periodicities are primarily induced by the semi-, quarter- and terdiurnal thermospheric tides, respectively. Our results also establish the systematic and widespread manifestation of shorter-scale (4.8- and 4-h) periodicities observed mainly for IDL and less frequently for Es only during December and January, in the nine years considered, which is most probably linked to higher-order solar tides. Graphical Abstract

1 citations