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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]

Real-time precise point positioning regional augmentation for large GPS reference networks / Xinging Li in GPS solutions, vol 18 n° 1 (january 2014)  

Public [article]  inGPS solutions > vol 18 n° 1 (january 2014) . - pp 61 - 71 Titre : Real-time precise point positioning regional augmentation for large GPS reference networks Type de document : Article/Communication Auteurs : Xinging Li, Auteur ; Maorong Ge, Auteur ; Jan Douša, Auteur Année de publication : 2014 Article en page(s) : pp 61 - 71 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] ambiguïté entière [Termes IGN] correction atmosphérique [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] réseau géodésique local Résumé : (auteur) An increasing number of GNSS reference stations are installed around the world to provide real-time precise positioning services. In most of the current services, a full network solution is required for the precise determination of biases. Such a network solution is time consuming and difficult to achieve for very large regions such as Europe or China. Therefore, we developed a multi-layer processing scheme for precise point positioning (PPP) regional augmentation to avoid processing large networks. Furthermore, we use L1 and L2 raw observations and estimate atmospheric delays, which were properly constrained to the atmospheric corrections derived from the reference stations. Therefore, inaccurate representation of atmospheric delays due to temporal and/or spatial atmospheric fluctuations in the processing can be compensated. The proposed scheme of PPP regional augmentation was implemented into the operational real-time PPP service system at GFZ for validation. The real-time orbit and clock corrections, the uncalibrated phase delays, and regional augmentation corrections are generated by this system. The augmentation corrections from the regional network are investigated and the positioning performance in terms of positioning accuracy and time for fixed solution is demonstrated in real-time. Our results indicate that a reliable fixing is possible after 5 s on average. The positioning accuracy is about 12, 10, and 25 mm in east, north, and vertical direction, respectively. Numéro de notice : A2014-664 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-013-0310-3 En ligne : https://doi.org/10.1007/s10291-013-0310-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=77824 [article]

Precise position determination using a Galileo E5 single-frequency receiver / H. Toho Diessongo in GPS solutions, vol 18 n° 1 (january 2014)  

Public [article]  inGPS solutions > vol 18 n° 1 (january 2014) . - pp 73 - 83 Titre : Precise position determination using a Galileo E5 single-frequency receiver Type de document : Article/Communication Auteurs : H. Toho Diessongo, Auteur ; Torben Schüler, Auteur ; Stefan Junker, Auteur Année de publication : 2014 Article en page(s) : pp 73 - 83 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] code GNSS [Termes IGN] positionnement par Galileo [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] retard ionosphèrique [Termes IGN] signal Galileo Résumé : (auteur) The European Galileo system offers one dedicated signal that is superior to all other signals currently available in space, namely the broadband signal E5. This signal has a bandwidth of at least 51 MHz using an AltBOC modulation. It features a code range noise at centimeter level. Additionally, the impact of multipath effects on this signal is significantly lower compared to all other available GNSS signals. These unique features of Galileo E5 drastically improve the precision of code range measurements and hence enable precise single-frequency positioning. Certain scientific and non-scientific applications in the positioning domain could likely benefit from the exploitation of E5 measurements. A positioning approach based on an additive combination of code range and carrier phase measurements (CPC—“code-plus-carrier”) to eliminate the ionospheric delay could be used to perform precise positioning over long distances. Unfortunately, this derived observable contains the ambiguity term as an additional unknown what normally requires longer observation windows in order to allow sufficient convergence of the ambiguity parameters. For this reason, a rapid convergence algorithm based on Kalman filtering was implemented in addition to the conventional CPC approach that is also discussed. The CPC-based results yield a positioning precision of 2–5 cm after a convergence time of about 3 h. The rapid convergence filter allows fixing the ambiguity terms within a few minutes, and the obtained position results are at the sub-decimeter level. Regarding one selected test, real data from Galileo experimental satellite GIOVE A were used in order to confirm our assumptions. However, since the current Galileo constellation is not sufficient for real-world positioning trials yet, all major results are based on simulated data. Numéro de notice : A2014-655 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-013-0311-2 En ligne : https://doi.org/10.1007/s10291-013-0311-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=77826 [article]