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Analysis of star camera errors in GRACE data and their impact on monthly gravity field models / Pedro Inácio in Journal of geodesy, vol 89 n° 6 (June 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 6 (June 2015) . - pp 551 - 571 Titre : Analysis of star camera errors in GRACE data and their impact on monthly gravity field models Type de document : Article/Communication Auteurs : Pedro Inácio, Auteur ; Pavel Ditmar, Auteur ; Roland Klees, Auteur ; Hassan Hashemi Farahani, Auteur Année de publication : 2015 Article en page(s) : pp 551 - 571 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] acquisition de données [Termes IGN] analyse diachronique [Termes IGN] anomalie de pesanteur [Termes IGN] capteur spatial [Termes IGN] champ de pesanteur terrestre [Termes IGN] données GRACE [Termes IGN] erreur de mesure [Termes IGN] impact sur les données [Termes IGN] modèle d'erreur [Termes IGN] orientation du capteur [Termes IGN] propagation d'erreur Résumé : (auteur) Star cameras (SCs) on board the GRACE satellites provide information about the attitudes of the spacecrafts. This information is needed to reduce the K-band ranging data to the centre of mass of the satellites. In this paper, we analyse GRACE SC errors using two months of real data of the primary and secondary SCs. We show that the errors consist of a harmonic component, which is highly correlated with the satellite’s true anomaly, and a stochastic component. We built models of both error components, and use these models for error propagation studies. Firstly, we analyse the propagation of SC errors into inter-satellite accelerations. A spectral analysis reveals that the stochastic component exceeds the harmonic component, except in the 3–10 mHz frequency band. In this band, which contains most of the geophysically relevant signal, the harmonic error component is larger than the random component. Secondly, we propagate SC errors into optimally filtered monthly mass anomaly maps and compare them with the total error. We found that SC errors account for about 18 % of the total error. Moreover, gaps in the SC data series amplify the effect of SC errors by a factor of 5. Finally, an analysis of inter-satellite pointing angles for GRACE data between 2003 and 2010 reveals that inter-satellite ranging errors were exceptionally large during the period February 2003 till May 2003. During these months, SC noise is amplified by a factor of 3 and is a considerable source of errors in monthly GRACE mass anomaly maps. In the context of future satellite gravity missions, the noise models developed in this paper may be valuable for mission performance studies. Numéro de notice : A2015-350 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0797-1 Date de publication en ligne : 03/03/2015 En ligne : https://doi.org/10.1007/s00190-015-0797-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76724 [article]

Network-based estimation of time-dependent noise in GPS position time series / Ksenia Dimitrieva in Journal of geodesy, vol 89 n° 6 (June 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 6 (June 2015) . - pp 591 - 606 Titre : Network-based estimation of time-dependent noise in GPS position time series Type de document : Article/Communication Auteurs : Ksenia Dimitrieva, Auteur ; Paul Segall, Auteur ; Charles DeMets, Auteur Année de publication : 2015 Article en page(s) : pp 591 - 606 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] bruit blanc [Termes IGN] bruit rose [Termes IGN] données GPS [Termes IGN] estimation statistique [Termes IGN] filtre de Kalman [Termes IGN] incertitude des données [Termes IGN] rapport signal sur bruit [Termes IGN] réseau géodésique local [Termes IGN] série temporelle [Termes IGN] signal GPS [Termes IGN] vitesse Résumé : (auteur) Some estimates of GPS velocity uncertainties are very low, Numéro de notice : A2015-351 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0801-9 Date de publication en ligne : 24/03/2015 En ligne : https://doi.org/10.1007/s00190-015-0801-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76736 [article]

Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo / Xinging Li in Journal of geodesy, vol 89 n° 6 (June 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 6 (June 2015) . - pp 607-635 Titre : Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo Type de document : Article/Communication Auteurs : Xinging Li, Auteur ; Maorong Ge, Auteur ; Xiaolei Dai, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 607-635 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] fiabilité des données [Termes IGN] orbitographie [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] signal BeiDou [Termes IGN] signal Galileo [Termes IGN] signal GLONASS [Termes IGN] signal GPS [Termes IGN] temps réel Résumé : (auteur) In this contribution, we present a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning. A rigorous multi-GNSS analysis is performed to achieve the best possible consistency by processing the observations from different GNSS together in one common parameter estimation procedure. Meanwhile, an efficient multi-GNSS real-time precise positioning service system is designed and demonstrated by using the multi-GNSS Experiment, BeiDou Experimental Tracking Network, and International GNSS Service networks including stations all over the world. The statistical analysis of the 6-h predicted orbits show that the radial and cross root mean square (RMS) values are smaller than 10 cm for BeiDou and Galileo, and smaller than 5 cm for both GLONASS and GPS satellites, respectively. The RMS values of the clock differences between real-time and batch-processed solutions for GPS satellites are about 0.10 ns, while the RMS values for BeiDou, Galileo and GLONASS are 0.13, 0.13 and 0.14 ns, respectively. The addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing, reduces the convergence time almost by 70 %, while the positioning accuracy is improved by about 25 %. Some outliers in the GPS-only solutions vanish when multi-GNSS observations are processed simultaneous. The availability and reliability of GPS precise positioning decrease dramatically as the elevation cutoff increases. However, the accuracy of multi-GNSS precise point positioning (PPP) is hardly decreased and few centimeter are still achievable in the horizontal components even with 40∘ elevation cutoff. At 30∘ and 40∘ elevation cutoffs, the availability rates of GPS-only solution drop significantly to only around 70 and 40 %, respectively. However, multi-GNSS PPP can provide precise position estimates continuously (availability rate is more than 99.5 %) even up to 40∘ elevation cutoff (e.g., in urban canyons). Numéro de notice : A2015-352 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0802-8 Date de publication en ligne : 14/03/2015 En ligne : https://doi.org/10.1007/s00190-015-0802-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76760 [article]