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GPS inter-frequency clock bias estimation for both uncombined and ionospheric-free combined triple-frequency precise point positioning / Lin Pan in Journal of geodesy, vol 93 n° 4 (April 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 4 (April 2019) . - pp 473 - 487 Titre : GPS inter-frequency clock bias estimation for both uncombined and ionospheric-free combined triple-frequency precise point positioning Type de document : Article/Communication Auteurs : Lin Pan, Auteur ; Xiaohong Zhang, Auteur ; Fei Guo, Auteur ; Jingnan Liu, Auteur Année de publication : 2019 Article en page(s) : pp 473 - 487 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] mesurage de phase [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur trifréquence Résumé : (Auteur) The time-varying biases within carrier phase observations will be integrated with satellite clock offset parameters in the precise clock estimation. The inconsistency among signal-dependent phase biases within a satellite results in the inadequacy of the current L1/L2 ionospheric-free (IF) satellite clock products for the GPS precise point positioning (PPP) involving L5 signal. The inter-frequency clock bias (IFCB) estimation approaches for triple-frequency PPP based on either uncombined (UC) observations or IF combined observations within a single arbitrary combination are proposed in this study. The key feature of the IFCB estimation approaches is that we only need to obtain a set of phase-specific IFCB (PIFCB) estimates between the L1/L5 and L1/L2 IF satellite clocks, and then, we can directly convert the obtained L1/L5 IF PIFCBs into L5 UC PIFCBs and L1/L2/L5 IF PIFCBs by multiplying individual constants. The mathematical conversion formula is rigorously derived. The UC and IF triple-frequency PPP models are developed. Datasets from 171 stations with a globally even distribution on seven consecutive days were adopted for analysis. After 24-h observation, the UC and IF triple-frequency PPP without PIFCB corrections can achieve an accuracy of 8, 6 and 13 mm, and 8, 5 and 13 mm in east, north and up coordinate components, respectively, while the corresponding positioning accuracy of the cases with PIFCB consideration can be improved by 38, 33 and 31%, and 50, 40 and 23% to 5, 4 and 9 mm, and 4, 3 and 10 mm in the three components, respectively. The corresponding improvement in convergence time is 17, 1 and 22% in the three components in UC model, respectively. Moreover, the phase observation residuals on L5 frequency in UC triple-frequency PPP and of L1/L2/L5 IF combination in IF triple-frequency PPP are reduced by about 4 mm after applying PIFCB corrections. The performance improvement in UC triple-frequency PPP over UC dual-frequency PPP is 7, 4 and 2% in terms of convergence time in the three components, respectively. The daily solutions of UC triple-frequency PPP have a comparable positioning accuracy to the UC dual-frequency PPP. Numéro de notice : A2019-155 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1176-5 Date de publication en ligne : 17/07/2018 En ligne : https://doi.org/10.1007/s00190-018-1176-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92494 [article]

Ambiguity resolved precise point positioning with GPS and BeiDou / Pan Li in Journal of geodesy, vol 91 n° 1 (January 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 1 (January 2017) . - pp 25 - 40 Titre : Ambiguity resolved precise point positioning with GPS and BeiDou Type de document : Article/Communication Auteurs : Pan Li, Auteur ; Xiaohong Zhang, Auteur ; Fei Guo, Auteur Année de publication : 2017 Article en page(s) : pp 25 - 40 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] combinaison au niveau des observations [Termes IGN] erreur systématique [Termes IGN] fractional cycle bias [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] simple différence Résumé : (Auteur) This paper focuses on the contribution of the global positioning system (GPS) and BeiDou navigation satellite system (BDS) observations to precise point positioning (PPP) ambiguity resolution (AR). A GPS + BDS fractional cycle bias (FCB) estimation method and a PPP AR model were developed using integrated GPS and BDS observations. For FCB estimation, the GPS + BDS combined PPP float solutions of the globally distributed IGS MGEX were first performed. When integrating GPS observations, the BDS ambiguities can be precisely estimated with less than four tracked BDS satellites. The FCBs of both GPS and BDS satellites can then be estimated from these precise ambiguities. For the GPS + BDS combined AR, one GPS and one BDS IGSO or MEO satellite were first chosen as the reference satellite for GPS and BDS, respectively, to form inner-system single-differenced ambiguities. The single-differenced GPS and BDS ambiguities were then fused by partial ambiguity resolution to increase the possibility of fixing a subset of decorrelated ambiguities with high confidence. To verify the correctness of the FCB estimation and the effectiveness of the GPS + BDS PPP AR, data recorded from about 75 IGS MGEX stations during the period of DOY 123-151 (May 3 to May 31) in 2015 were used for validation. Data were processed with three strategies: BDS-only AR, GPS-only AR and GPS + BDS AR. Numerous experimental results show that the time to first fix (TTFF) is longer than 6 h for the BDS AR in general and that the fixing rate is usually less than 35 % for both static and kinematic PPP. An average TTFF of 21.7 min and 33.6 min together with a fixing rate of 98.6 and 97.0 % in static and kinematic PPP, respectively, can be achieved for GPS-only ambiguity fixing. For the combined GPS + BDS AR, the average TTFF can be shortened to 16.9 min and 24.6 min and the fixing rate can be increased to 99.5 and 99.0 % in static and kinematic PPP, respectively. Results also show that GPS + BDS PPP AR outperforms single-system PPP AR in terms of convergence time and position accuracy. Numéro de notice : A2017-059 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0935-4 En ligne : http://dx.doi.org/10.1007/s00190-016-0935-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84267 [article]

Modeling and assessment of triple-frequency BDS precise point positioning / Fei Guo in Journal of geodesy, vol 90 n° 11 (November 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 11 (November 2016) . - pp 1223 - 1235 Titre : Modeling and assessment of triple-frequency BDS precise point positioning Type de document : Article/Communication Auteurs : Fei Guo, Auteur ; Xiaohong Zhang, Auteur ; Jinling Wang, Auteur ; Xiaodong Ren, Auteur Année de publication : 2016 Article en page(s) : pp 1223 - 1235 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données BeiDou [Termes IGN] fréquence multiple [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] signal BeiDou Résumé : (Auteur) The latest generation of GNSS satellites such as GPS BLOCK-IIF, Galileo and BDS are transmitting signals on three or more frequencies, thus having more choices in practice. At the same time, new challenges arise for integrating the new signals. This paper contributes to the modeling and assessment of triple-frequency PPP with BDS data. First, three triple-frequency PPP models are developed. The observation model and stochastic model are designed and extended to accommodate the third frequency. In particular, new biases such as differential code biases and inter-frequency biases as well as the parameterizations are addressed. Then, the relationships between different PPP models are discussed. To verify the triple-frequency PPP models, PPP tests with real triple-frequency data were performed in both static and kinematic scenarios. Results show that the three triple-frequency PPP models agree well with each other. Additional frequency has a marginal effect on the positioning accuracy in static PPP tests. However, the benefits of third frequency are significant in situations of where there is poor tracking and contaminated observations on frequencies B1 and B2 in kinematic PPP tests. Numéro de notice : A2016-799 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0920-y En ligne : http://dx.doi.org/10.1007/s00190-016-0920-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82579 [article]

Real-time clock jump compensation for precise point positioning / Fei Guo in GPS solutions, vol 18 n° 1 (january 2014)  

Public [article]  inGPS solutions > vol 18 n° 1 (january 2014) . - pp 41 - 50 Titre : Real-time clock jump compensation for precise point positioning Type de document : Article/Communication Auteurs : Fei Guo, Auteur ; Xiaohong Zhang, Auteur Année de publication : 2014 Article en page(s) : pp 41 - 50 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] format RINEX [Termes IGN] horloge [Termes IGN] paramètre de temps [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur GPS Résumé : (auteur) Over the past decades, a number of methods have been proposed to handle cycle slips in the carrier phase measurements, but few researches have investigated receiver clock jumps, which may produce undesirable effects on GPS data processing. Such events are generally ignored in double-differenced positioning. For undifferenced processing, such as precise point positioning (PPP) techniques, it is unwise to neglect the impact of clock jumps. Failure to properly detect and account for receiver clock jumps may sometimes cause unexpected behavior of the GPS software and large errors in the resulting PPP solution. This is particularly troublesome when there are irregular (types 2 or 3) millisecond clock jumps represented in RINEX observation files. In this study, we first provide an intuitive description of the receiver clock jump phenomenon, and a comprehensive classification of clock jumps is presented according to its influence on three fundamental quantities (time tag, pseudorange, and carrier phase) of RINEX observation files. To follow the RINEX convention, the observable consistency is analyzed for various types of clock jump; and a simple but robust real-time clock jump compensation (RTCJC) method is proposed for reconstructing a consistent set of observables. Numerous validation tests with various GPS data show that the method is applicable to millisecond clock jumps. Without RTCJC, clock jumps are prone to cause failure of gross error and cycle slip detection algorithms and so result in repeated re-initialization or even non-convergent solutions, which lead to gross errors in the PPP solution. When RTCJC is applied, all clock jumps present in the GPS data can be effectively identified and repaired accurately, and the problem of re-initialization in PPP will no longer be triggered by receiver clock jumps, which results in significant improvement of PPP accuracy and reliability. Numéro de notice : A2014-663 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-012-0307-3 En ligne : https://doi.org/10.1007/s10291-012-0307-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=77822 [article]