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Establishing a high-precision real-time ZTD model of China with GPS and ERA5 historical data and its application in PPP / Pengfei Xia in GPS solutions, vol 27 n° 1 (January 2023)  

Public [article]  inGPS solutions > vol 27 n° 1 (January 2023) . - n° 2 Titre : Establishing a high-precision real-time ZTD model of China with GPS and ERA5 historical data and its application in PPP Type de document : Article/Communication Auteurs : Pengfei Xia, Auteur ; Mengxiang Tong, Auteur ; Shirong Ye, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 2 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] Chine [Termes IGN] correction troposphérique [Termes IGN] données météorologiques [Termes IGN] grille [Termes IGN] positionnement ponctuel précis [Termes IGN] retard troposphérique zénithal [Termes IGN] série de Fourier [Termes IGN] série temporelle [Termes IGN] station GNSS [Termes IGN] temps de convergence [Termes IGN] temps réel [Termes IGN] variation diurne Résumé : (auteur) A high-precision real-time troposphere model is constructed by combining ground-based GNSS observation data and the latest European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5). First, the zenith tropospheric delay (ZTD) is extracted in real time with high accuracy by combining the data of more than 500 GNSS stations in the Crustal Movement Observation Network of China (CMONOC) and national reference station network (NRSN); second, a grid model of the elevation normalization model (ENM) in China using ERA5 data is constructed, which takes into account the annual, semiannual and daily cycles. The ZTD estimated by GNSS stations at different heights based on precise point positioning (PPP) is normalized to a uniform height based on ENM; in addition, the optimal smoothing factors of the Gauss distance weighting function in different seasons are determined based on ERA5, which contributes to improved accuracy of ZTD interpolated from GNSS-derived ZTD to ZTD at grid points; finally, a real-time 1° × 1°ZTD grid model of China is created; the broadcast interval is extended to 6 min from few seconds. The new ZTD model has been evaluated using the data of 15 GNSS stations in China in 2020. The test results show that the new ZTD model deviates from the reference value with a mean value better than − 0.09 cm and RMSE, better than 1.44 cm compared with the ZTD estimated by post-processing GNSS, while the mean value of the deviation is -0.13 cm, and the RMSE is approximately 3.11 cm compared with radiosonde-derived ZTD. The new ZTD grid model can be used to enhance GNSS/PPP. Two weeks of GNSS observations, one week in winter and another in summer, were randomly collected for PPP processing. The statistical results show the convergence time in the vertical directions is shortened by 37.4% and 38.6% at the 95% and 68% confidence levels after ZTD constraints are applied to the float PPP solution, respectively. Numéro de notice : A2023-004 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01338-9 Date de publication en ligne : 07/10/2022 En ligne : https://doi.org/10.1007/s10291-022-01338-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101874 [article]

Exploration and analysis of the factors influencing GNSS PWV for nowcasting applications / Min Guo in Advances in space research, vol 67 n° 12 (15 June 2021)  

Public [article]  inAdvances in space research > vol 67 n° 12 (15 June 2021) . - pp 3960 - 3978 Titre : Exploration and analysis of the factors influencing GNSS PWV for nowcasting applications Type de document : Article/Communication Auteurs : Min Guo, Auteur ; Hanwei Zhang, Auteur ; Pengfei Xia, Auteur Année de publication : 2021 Article en page(s) : pp 3960 - 3978 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] brouillard [Termes IGN] données GNSS [Termes IGN] données météorologiques [Termes IGN] Pékin (Chine) [Termes IGN] retard troposphérique zénithal [Termes IGN] surveillance météorologique [Termes IGN] température de surface [Termes IGN] vapeur d'eau Résumé : (auteur) Precipitable water vapor (PWV) can be assimilated into a numerical weather model (NWM) to improve the prediction accuracy of numerical weather prediction. In this study, taking GNSS data for the Beijing Fangshan station (BJFS) as an example, based on the method of Pearson correlation coefficient combined with quantitative analysis, GNSS datasets are used to study the relationships between GNSS-derived PWV (GNSS PWV_Met) and its influencing factors, including the internal influencing factors zenith troposphere delay (ZTD), zenith hydrostatic delay (ZHD), zenith wet delay (ZWD), and surface temperature (Ts), and the external influencing factor haze (mainly PM2.5). Firstly, based on the strong correlation between PWV_Met and ZTD hourly sequences from the International GNSS Service Network’s BJFS station for DOYS 182–212, 2015, the results of experiment prove that the reliability of GNSS ZTD is used to forecast PWV_Met in short-term forecasting. Secondly, based on hourly data of BJFS in 2016, the correlation between PWV_Met and ZTD, ZWD, ZHD, pressure (P) and Ts is analyzed, and then, with the rate of ZTD variation as the main factor, ZTD variation as auxiliary factor, the prediction success rate is 88.24% from hourly data of precipitation event for DOYs 183–213 in Beijing. The experiment indicates that ZTD can help forecast short-term precipitation. Thirdly, based on data from three hazy periods with relatively stable weather conditions, no heavy rainfall, and relatively continuous data in the past three years, the correlation between GNSS PWV_Met/ZTD and PM2.5 hourly series is analyzed. The results of the experiments suggests that GNSS ZTD should be considered to assist in haze monitoring. So in the absence of radiosonde stations and meteorological elements, ZTDs on retrieval of GNSS stations have more application value in short-term forecast. Numéro de notice : A2021-947 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1016/j.asr.2021.02.018 Date de publication en ligne : 06/05/2021 En ligne : https://doi.org/10.1016/j.asr.2021.02.018 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99763 [article]

Assessing the latest performance of Galileo-only PPP and the contribution of Galileo to Multi-GNSS PPP / Fengyu Xiu in Advances in space research, vol 63 n° 9 (1 May 2019)  

Public [article]  inAdvances in space research > vol 63 n° 9 (1 May 2019) . - pp 2784 - 2795 Titre : Assessing the latest performance of Galileo-only PPP and the contribution of Galileo to Multi-GNSS PPP Type de document : Article/Communication Auteurs : Fengyu Xiu, Auteur ; Shirong Ye, Auteur ; Pengfei Xia, Auteur ; Lewen Zhao, Auteur ; et al., Auteur Année de publication : 2019 Article en page(s) : pp 2784 - 2795 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] constellation Galileo [Termes IGN] erreur systématique inter-systèmes [Termes IGN] GalileoSat [Termes IGN] positionnement cinématique [Termes IGN] positionnement par Galileo [Termes IGN] positionnement par GLONASS [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] résidu [Termes IGN] trajet multiple [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) By the end of 2016, the Galileo constellation had 4 in-orbit validation (IOV) satellites and 14 full operational capability (FOC) satellites, 17 of which were able to transmit signal in November 2017. Galileo has already had early operational capability (EOC). To assess the latest performance of the Galileo-only precise point positioning (PPP) and the contribution of Galileo to the Multi-GNSS PPP solutions, observations collected at 16 Multi-GNSS Experiment (MGEX) stations over ten days are used to realize the various PPP cases. The statistical results show that the three-dimensional positioning accuracy of Galileo static and kinematic PPP can reach centimeter level and decimeter level after convergence, respectively. The contribution of Galileo can improve the positioning accuracy by 29.49%, 29.96% and 23.70% for GPS kinematic PPP and 11.03%, 10.59% and 11.07% for GPS/GLONASS kinematic PPP solutions in the north, east and up components, respectively. The average convergence time can be reduced by 45.48% for GPS-only kinematic PPP and by 11.04% for GPS/GLONASS solutions by adding Galileo observations. Moreover, adding Galileo observations shortens the average convergence time by 30.45% and 7.8% for GPS-only and GPS/GLONASS static PPP solutions, respectively. Although the convergent positioning results of GPS and GPS/GLONASS static PPP solutions after the addition of Galileo measurements do not demonstrate as significant improvement as those of the kinematic PPP solutions, the positioning accuracy of the GPS/Galileo static PPP solutions compared to the GPS-only static PPP still demonstrates an improvement of approximately 25% on the east component. Furthermore, the GPS/Galileo internal system time bias (ISB) and observation residual are analyzed. The results show that the noise level of the GPS L1/L2 signals and the negative impact of multipath errors on the GPS pseudo-range observations for the L1/L2 signals are greater than those of Galileo E1/E5a signals, resulting in the residuals of GPS ionosphere-free code observations larger than those of Galileo code observations. However, the phase observation residuals of GPS and Galileo are of the same magnitude. Additionally, the one-day GPS/Galileo ISB is quite stable. Its stability described by standard deviation is approximately 0.34 ns. Numéro de notice : A2019-397 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2018.06.008 Date de publication en ligne : 28/06/2019 En ligne : https://doi.org/10.1016/j.asr.2018.06.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93508 [article]