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Estimation of code observation-specific biases (OSBs) for the modernized multi-frequency and multi-GNSS signals: an undifferenced and uncombined approach / Teng Liu in Journal of geodesy, vol 95 n° 8 (August 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 8 (August 2021) . - n° 97 Titre : Estimation of code observation-specific biases (OSBs) for the modernized multi-frequency and multi-GNSS signals: an undifferenced and uncombined approach Type de document : Article/Communication Auteurs : Teng Liu, Auteur ; Baocheng Zhang, Auteur Année de publication : 2021 Article en page(s) : n° 97 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] code GNSS [Termes IGN] combinaison linéaire [Termes IGN] erreur systématique de code différentiel [Termes IGN] fréquence multiple [Termes IGN] phase GNSS [Termes IGN] retard ionosphèrique [Termes IGN] signal GNSS [Termes IGN] teneur verticale totale en électrons [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) For a long time, code biases of global navigation satellite system (GNSSs) have been parameterized and presented in the differential mode, namely the commonly-known differential code biases (DCB). However, with the continuous modernization of the existing constellations and rapid developments of the new systems, various new frequencies and types of GNSS signals are emerging, which makes the traditional DCB mode less flexible and efficient to handle the new situations and challenges. Recently, code biases in observation-specific representation, which finally provides observation-specific biases (OSBs), turns out to be a good solution and is gradually accepted by the GNSS community, though existing products are generated based on routine procedures and few studies concentrate on the new methods. In view of it, this study aims to propose a rigorous, flexible and efficient approach of OSB estimation for the modernized multi-frequency and, multi-GNSS signals. To achieve this, instead of being-based on linear combinations of raw observations in the existing literature, an extended multi-frequency geometry-free model is first established based on undifferenced and uncombined observations, which can adapt to observations of arbitrary frequencies and types in a compatible and flexible way and is used to extract the various types of linear combinations of the interested OSBs. Then, regarding the previously-obtained linear combinations as virtual observables after station-based ionosphere modeling, all OSB parameters are setup and estimated in a single normal equation, during which a clear identification and elimination of the rank deficiencies in the linear system is carefully conducted by introducing different types of constraints. The proposed new method is validated with one month of real data to generate totally 32 types of OSBs for GPS, GLONASS, Galileo, BeiDou, and QZSS. The estimated OSBs are compared with existing OSB and DCB products from other agencies. Results indicate that the proposed method can be used as a flexible and precise method for full-constellation and full-type OSB estimation. Numéro de notice : A2021-584 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01549-x Date de publication en ligne : 12/08/2021 En ligne : https://doi.org/10.1007/s00190-021-01549-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98199 [article]

Review of code and phase biases in multi-GNSS positioning / Martin Håkansson in GPS solutions, vol 21 n° 3 (July 2017)  

Public [article]  inGPS solutions > vol 21 n° 3 (July 2017) . - pp 849 - 860 Titre : Review of code and phase biases in multi-GNSS positioning Type de document : Article/Communication Auteurs : Martin Håkansson, Auteur ; Anna B. O. Jensen, Auteur ; Milan Horemuz, Auteur ; Gunnar Hedling, Auteur Année de publication : 2017 Article en page(s) : pp 849 - 860 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] code GNSS [Termes IGN] correction du signal [Termes IGN] données GNSS [Termes IGN] modèle ionosphérique [Termes IGN] phase GNSS [Termes IGN] positionnement par GNSS [Termes IGN] précision du positionnement [Termes IGN] récepteur GNSS [Termes IGN] résolution d'ambiguïté Résumé : (auteur) A review of the research conducted until present on the subject of Global Navigation Satellite System (GNSS) hardware-induced phase and code biases is here provided. Biases in GNSS positioning occur because of imperfections and/or physical limitations in the GNSS hardware. The biases are a result of small delays between events that ideally should be simultaneous in the transmission of the signal from a satellite or in the reception of the signal in a GNSS receiver. Consequently, these biases will also be present in the GNSS code and phase measurements and may there affect the accuracy of positions and other quantities derived from the observations. For instance, biases affect the ability to resolve the integer ambiguities in Precise Point Positioning (PPP), and in relative carrier phase positioning when measurements from multiple GNSSs are used. In addition, code biases affect ionospheric modeling when the Total Electron Content is estimated from GNSS measurements. The paper illustrates how satellite phase biases inhibit the resolution of the phase ambiguity to an integer in PPP, while receiver phase biases affect multi-GNSS positioning. It is also discussed how biases in the receiver channels affect relative GLONASS positioning with baselines of mixed receiver types. In addition, the importance of code biases between signals modulated onto different carriers as is required for modeling the ionosphere from GNSS measurements is discussed. The origin of biases is discussed along with their effect on GNSS positioning, and descriptions of how biases can be estimated or in other ways handled in the positioning process are provided. Numéro de notice : A2017-438 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0572-7 En ligne : https://doi.org/10.1007/s10291-016-0572-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86348 [article]

Optimal Doppler-aided smoothing strategy for GNSS navigation / Zebo Zhou in GPS solutions, vol 21 n° 1 (January 2017)  

Public [article]  inGPS solutions > vol 21 n° 1 (January 2017) . - pp 197 - 210 Titre : Optimal Doppler-aided smoothing strategy for GNSS navigation Type de document : Article/Communication Auteurs : Zebo Zhou, Auteur ; Bofeng Li, Auteur Année de publication : 2017 Article en page(s) : pp 197 - 210 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] code GNSS [Termes IGN] données Doppler [Termes IGN] glissement de cycle [Termes IGN] onde porteuse [Termes IGN] phase Résumé : (Auteur) Carrier-phase-smoothed code (CPSC), i.e., smoothing of the code using carrier phases, has widely been used to reduce the code noise in GNSS applications. However, the efficiency of CPSC suffers significantly from cycle slips, interruptions and jitters. The GNSS Doppler, as an instantaneous measurement, is robust and immune to cycle slips and proven useful in GNSS-challenged environments. We develop optimal Doppler-smoothed code based on the principle of minimum variance using the Hatch filter for two typical applications, which are called pure Doppler-smoothed code (PDSC) and continued Doppler-smoothed code. PDSC results from smoothing the code using only Doppler, whereas in case of continued Doppler-smoothed code, the smoothing continues using Doppler once the carrier phase becomes unavailable. Furthermore, in order to refine the Doppler-smoothed code model, a balance factor is introduced for adjusting the contributions of raw code and Doppler measurements to the smoothed code in case the Doppler noise is relatively large. Finally, experiments are carried out to demonstrate the performance of the theory, which verifies its validity and efficiency. Numéro de notice : A2017-016 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0512-y Date de publication en ligne : 20/01/2016 En ligne : https://doi.org/10.1007/s10291-015-0512-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83947 [article]

An advanced GNSS code multipath detection and estimation algorithm / Negin Sokhandan in GPS solutions, vol 20 n° 4 (October 2016)  

Public [article]  inGPS solutions > vol 20 n° 4 (October 2016) . - pp 627 - 640 Titre : An advanced GNSS code multipath detection and estimation algorithm Type de document : Article/Communication Auteurs : Negin Sokhandan, Auteur ; James T. Curran, Auteur ; Ali Broumandan, Auteur ; Gérard Lachapelle, Auteur Année de publication : 2016 Article en page(s) : pp 627 - 640 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] code GNSS [Termes IGN] méthode du maximum de vraisemblance (estimation) [Termes IGN] milieu urbain [Termes IGN] modèle de simulation [Termes IGN] positionnement par GNSS [Termes IGN] système de navigation [Termes IGN] trajet multiple Résumé : (Auteur) A novel maximum likelihood-based range estimation algorithm is designed to provide robustness to multipath, which is recognized as a dominant error source in DS-CDMA-based navigation systems. The detection–estimation problem is jointly solved to sequentially estimate the parameters of each individual multipath component and predict the existence of a next possible component. A comparison between contemporary maximum likelihood-based multipath estimation techniques and this new technique is provided. A selection of realistic channel simulation models is used to assess relative performance under different operating situations. A set of real GPS L1/CA data processing results are also presented to further assess the applicability of the proposed algorithm for urban navigation. Numéro de notice : A2016--025 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0475-z En ligne : http://dx.doi.org/10.1007/s10291-015-0475-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83926 [article]

Ionospheric tomography using GNSS: multiplicative algebraic reconstruction technique applied to the area of Brazil / Fabricio Dos Santos Prol in GPS solutions, vol 20 n° 4 (October 2016)  

Public [article]  inGPS solutions > vol 20 n° 4 (October 2016) . - pp 807 - 814 Titre : Ionospheric tomography using GNSS: multiplicative algebraic reconstruction technique applied to the area of Brazil Type de document : Article/Communication Auteurs : Fabricio Dos Santos Prol, Auteur ; Paulo de Oliveira Camargo, Auteur Année de publication : 2016 Article en page(s) : pp 807 - 814 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Brésil [Termes IGN] code GNSS [Termes IGN] International Reference Ionosphere [Termes IGN] modèle ionosphérique [Termes IGN] phase GNSS [Termes IGN] récepteur GNSS [Termes IGN] teneur totale en électrons [Termes IGN] tomographie par GPS Résumé : (Auteur) Experimental analysis was performed using multiplicative algebraic reconstruction technique (MART) to map the ionosphere over Brazil. Code and phase observations from the global navigation satellite system (GNSS) together with the international reference ionosphere (IRI) enabled the estimation of ionospheric profiles and total electron content (TEC) over the entire region. Twenty-four days of data collected from existing ground-based GNSS receivers during the recent solar maximum period were used to analyze the performance of the MART algorithm. The results were compared with four ionosondes. It was demonstrated that MART estimated the electron density peak with the same degree of accuracy as the IRI model in regions with appropriate geometrical coverage by GNSS receivers for tomographic reconstruction. In addition, the slant TEC, as estimated with MART, presented lower root-mean-square error than the TEC calculated by ionospheric maps available from the International GNSS Service (IGS). Furthermore, the daily variations of the ionosphere were better represented with the algebraic techniques, compared to the IRI model and IGS maps, enabling a correlation of the elevation of the ionosphere at higher altitudes with the equatorial ionization anomaly intensification. The tomographic representations also enabled the detection of high vertical gradients at the same instants in which ionospheric irregularities were evident. Numéro de notice : A2016--030 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0490-0 En ligne : http://dx.doi.org/10.1007/s10291-015-0490-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83932 [article]

A comparative analysis of measurement noise and multipath for four constellations: GPS, BeiDou, GLONASS and Galileo / Changsheng Cai in Survey review, vol 48 n° 349 (July 2016)  

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Determination of differential code biases with multi-GNSS observations / Ningbo Wang in Journal of geodesy, vol 90 n° 3 (March 2016)  

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

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