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Multi-GNSS real-time precise clock estimation considering the correction of inter-satellite code biases / Liang Chen in GPS solutions, vol 25 n° 2 (April 2021)  

Public [article]  inGPS solutions > vol 25 n° 2 (April 2021) . - 17 p. Titre : Multi-GNSS real-time precise clock estimation considering the correction of inter-satellite code biases Type de document : Article/Communication Auteurs : Liang Chen, Auteur ; Min Li, Auteur ; Ying Zhao, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : 17 p. Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction [Termes IGN] décalage d'horloge [Termes IGN] erreur systématique inter-systèmes [Termes IGN] phase [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par Galileo [Termes IGN] positionnement par GLONASS [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] récepteur GNSS [Termes IGN] temps réel Résumé : (Auteur) For reasons mostly related to chip shape distortions, global navigation satellite system (GNSS) observations are corrupted by receiver-dependent biases. These are often stable in the long term, though numerically different depending on the signal frequency, satellite system and receiver manufacturer. Based on the mixed-differenced model combining undifferenced pseudorange with epoch-differenced carrier phase observations, we present a multi-GNSS real-time precise clock estimation model considering correction of inter-satellite code biases (ISCBs). Pre-estimated receiver-dependent ISCB corrections are introduced to correct the inter-receiver, inter-satellite and inter-system biases largely. Then the number of estimated parameters is reduced to a manageable level for real-time estimation. Comparisons with post-processed data show that compared to undifferenced, epoch-differenced and non-bias-corrected mixed-differenced models, the proposed bias-corrected model can greatly reduce the precise clock offset systematic biases, especially for GLONASS and BeiDou. The test results show the root mean square data reductions are improved by up to 96% for GLONASS, 78% for BeiDou and 40% for GPS and Galileo. Numéro de notice : A2021-092 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01065-z date de publication en ligne : 15/01/2021 En ligne : https://doi.org/10.1007/s10291-020-01065-z Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96883 [article]

Influence of stochastic modeling for inter-system biases on multi-GNSS undifferenced and uncombined precise point positioning / Feng Zhou in GPS solutions, vol 23 n° 3 (July 2019)  

Public [article]  inGPS solutions > vol 23 n° 3 (July 2019) Titre : Influence of stochastic modeling for inter-system biases on multi-GNSS undifferenced and uncombined precise point positioning Type de document : Article/Communication Auteurs : Feng Zhou, Auteur ; Danan Dong, Auteur ; Xin Li, Auteur ; Harald Schuh, Auteur Année de publication : 2019 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] bruit blanc [Termes IGN] décalage d'horloge [Termes IGN] erreur systématique inter-systèmes [Termes IGN] estimation statistique [Termes IGN] modèle stochastique [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis Résumé : (auteur) The focus of this study is on proper modeling of the dynamics for inter-system biases (ISBs) in multi-constellation Global Navigation Satellite System (GNSS) precise point positioning (PPP) processing. First, the theoretical derivation demonstrates that the ISBs originate from not only the receiver-dependent hardware delay differences among different GNSSs but also the receiver-independent time differences caused by the different clock datum constraints among different GNSS satellite clock products. Afterward, a comprehensive evaluation of the influence of ISB stochastic modeling on undifferenced and uncombined PPP performance is conducted, i.e., random constant, random walk process, and white noise process are considered. We use data based on a 1-month period (September 2017) Multi-GNSS Experiment (MGEX) precise orbit and clock products from four analysis centers (CODE, GFZ, CNES, and WHU) and 160 MGEX tracking stations. The results demonstrate that generally, the positioning performance of PPP in terms of convergence time and positioning accuracy with the final products from CODE, CNES, and WHU is comparable among the three ISB handling schemes. However, estimating ISBs as random walk process or white noise process outperforms that as the random constant when using the GFZ products. These results indicate that the traditional estimation of ISBs as the random constant may not always be reasonable in multi-GNSS PPP processing. To achieve more reliable positioning results, it is highly recommended to consider the ISBs as random walk process or white noise process in multi-GNSS PPP processing. Numéro de notice : A2019-199 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-019-0852-0 date de publication en ligne : 09/04/2019 En ligne : https://doi.org/10.1007/s10291-019-0852-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92654 [article]

Multi-dimensional particle filter-based estimation of inter-system phase biases for multi-GNSS real-time integer ambiguity resolution / Yumiao Tian in Journal of geodesy, vol 93 n°7 (July 2019)  

Public [article]  inJournal of geodesy > vol 93 n°7 (July 2019) . - pp 1073 - 1087 Titre : Multi-dimensional particle filter-based estimation of inter-system phase biases for multi-GNSS real-time integer ambiguity resolution Type de document : Article/Communication Auteurs : Yumiao Tian, Auteur ; Zhizhao Liu, Auteur ; Frank Neitzel, Auteur Année de publication : 2019 Article en page(s) : pp 1073 - 1087 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] ambiguïté entière [Termes IGN] analyse multidimensionnelle [Termes IGN] constellation GNSS [Termes IGN] erreur systématique inter-systèmes [Termes IGN] filtre [Termes IGN] phase GNSS [Termes IGN] positionnement par GNSS [Termes IGN] précision du positionnement [Termes IGN] résolution d'ambiguïté [Termes IGN] temps réel [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) In multi-GNSS integration, fixing inter-system double-difference ambiguities to integers is still a challenge due to the existence of inter-system biases (ISB) when mixed types of GNSS receivers are used. It has been shown that when ISB is known, the inter-system ambiguities can be fixed and the reliability of ambiguity fixing can be improved significantly, especially under poor conditions when the number of observed satellites is small. In traditional methods, the intra-system ambiguity is fixed first; then, the ISB is estimated to ultimately fix the inter-system ambiguity. In our work, we use the particle filter-based method to estimate the ISB parameter and fix the inter-system ambiguities to integers at the same time. This method shows higher reliability and higher ambiguity fixing rate. Nevertheless, the existing particle filter approach for ISB parameter estimation is a one-dimensional algorithm. When satellites from three or more systems are observed, there are two or more ISB parameters. We extend the current one-dimensional particle filter approach to multi-dimensional case and estimate multi-ISB parameters in this study. We first present a multi-dimensional particle filter approach that can estimate multi-ISB parameters simultaneously. We also show that the RATIO values can be employed to judge the quality of multi-dimensional ISB values. Afterward, a two-dimensional particle filter approach is taken as an example to validate this approach. For example, in the experiment of GPS L5, Galileo E5a and QZSS L5 integration with 6 satellites using the IGS baseline SIN0-SIN1, only three ambiguities are resolved to integer when the ISBs are unknown. The integer ambiguity fixing rate is 41.0% with 53% of the ambiguity-fixed solutions having positioning errors larger than 3 cm. However, when our approach is adopted, the number of integer ambiguity parameters increases to five. The integer ambiguity fixing rate increases to 99.7% with 100% of ambiguity-fixed solutions having positioning errors smaller than 3 cm. Numéro de notice : A2019-359 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-01226-6 date de publication en ligne : 29/01/2019 En ligne : https://doi.org/10.1007/s00190-018-01226-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93427 [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]

Accounting for the differential inter-system bias (DISB) of code observation in GPS+BDS positioning / Xiang Cao in Journal of applied geodesy, vol 13 n° 1 (January 2019)  

Public [article]  inJournal of applied geodesy > vol 13 n° 1 (January 2019) . - pp 63 - 68 Titre : Accounting for the differential inter-system bias (DISB) of code observation in GPS+BDS positioning Type de document : Article/Communication Auteurs : Xiang Cao, Auteur ; Qing Wang, Auteur ; Chengfa Gao, Auteur ; Jie Zhang, Auteur Année de publication : 2019 Article en page(s) : pp 63 - 68 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur systématique inter-systèmes [Termes IGN] mesurage de pseudo-distance [Termes IGN] positionnement différentiel [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GPS [Termes IGN] temps réel Résumé : (Auteur) If the associated differential inter-system biases (DISBs) are priori known, only one common reference satellite is sufficient, which is called the inter-system model. The inter-system model can help to maximize the redundancy of the positioning model, and thus can improve the positioning performance, especially in harsh environment. However, in practice use not all receivers can be calibrated with DISBs in advance. In this paper, taking combined GPS and BDS pseudorange positioning as the example, we compare three positioning models and their positioning performance. One is traditional intra-system model, and the other two belongs to the inter-system models, i. e. the model with calibration of DISB and the model with real-time estimation of DISB parameter. Positioning performance using the three models is evaluated with simulated obstructed environments. It will be shown that besides the model with calibration of DISB, the model with real-time estimation of DISB parameter can also effectively improve positioning accuracy and reliability compared with the traditional intra-system model, especially for the severely obstructed environment with only a few satellites observed. When no more than 7 satellites visible, the positioning accuracies in each directions can be improved by no less than 15 %. The proposed model can be used alternatively when no priori DISB calibration is available. Numéro de notice : A2019-135 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2018-0025 date de publication en ligne : 30/08/2018 En ligne : https://doi.org/10.1515/jag-2018-0025 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92465 [article]

Evaluation of three ionospheric delay computation methods for ground-based GNSS receivers / Liang Chen in GPS solutions, vol 22 n° 4 (October 2018)  

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Consistent realization of celestial and terrestrial reference frames / Younghee Kwak in Journal of geodesy, vol 92 n° 9 (September 2018)  

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Determining inter-system bias of GNSS signals with narrowly spaced frequencies for GNSS positioning / Yumiao Tian in Journal of geodesy, vol 92 n° 8 (August 2018)  

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Positioning stability improvement with inter-system biases on multi-GNSS PPP / Byung-Kyu Choi in Journal of applied geodesy, vol 12 n° 3 (July 2018)  

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GPS, Galileo, QZSS and IRNSS differential ISBs: estimation and application / Dennis Odijk in GPS solutions, vol 21 n° 2 (April 2017)  

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Multi-GNSS precise point positioning (MGPPP) using raw observations / Teng Liu in Journal of geodesy, vol 91 n° 3 (March 2017)  

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GPS/BDS short-term ISB modelling and prediction / Nan Jiang in GPS solutions, vol 21 n° 1 (January 2017)  

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A statistical characterization of the Galileo-to-GPS inter-system bias / Ciro Gioia in Journal of geodesy, vol 90 n° 11 (November 2016)  

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