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Stochastic modeling of triple-frequency BeiDou signals: estimation, assessment and impact analysis / Bofeng Li in Journal of geodesy, vol 90 n° 7 (July 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 7 (July 2016) . - pp 593 – 610 Titre : Stochastic modeling of triple-frequency BeiDou signals: estimation, assessment and impact analysis Type de document : Article/Communication Auteurs : Bofeng Li, Auteur Année de publication : 2016 Article en page(s) : pp 593 – 610 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] données BeiDou [Termes IGN] erreur instrumentale [Termes IGN] modèle stochastique [Termes IGN] orbite géostationnaire [Termes IGN] positionnement par GNSS [Termes IGN] récepteur trifréquence [Termes IGN] résolution d'ambiguïté Résumé : (auteur) Stochastic models are important in global navigation satellite systems (GNSS) estimation problems. One can achieve reliable ambiguity resolution and precise positioning only by use of a suitable stochastic model. The BeiDou system has received increased research focus, but based only on empirical stochastic models from the knowledge of GPS. In this paper, we will systematically study the estimation, assessment and impacts of a triple-frequency BeiDou stochastic model. In our estimation problem, a single-difference, geometry-free functional model is used to extract pure random noise. A very sophisticated structure of unknown variance matrix is designed to allow the estimation of satellite-specific variances, cross correlations between two arbitrary frequencies, as well as the time correlations for phase and code observations per frequency. In assessing the stochastic models, six data sets with four brands of BeiDou receivers on short and zero-length baselines are processed, and the results are compared. In impact analysis of stochastic model, the performance of integer ambiguity resolution and positioning are numerically demonstrated using a realistic stochastic model. The results from ultrashort (shorter than 10 m) and zero-length baselines indicate that BeiDou stochastic models are affected by both observation and receiver brands. The observation variances have been modeled by an elevation-dependent function, but the modeling errors for geostationary earth orbit (GEO) satellites are larger than for inclined geosynchronous satellite orbit (IGSO) and medium earth orbit (MEO) satellites. The stochastic model is governed by both the internal errors of the receiver and external errors at the site. Different receivers have different capabilities for resisting external errors. A realistic stochastic model is very important for achieving ambiguity resolution with a high success rate and small false alarm and for determining realistic variances for position estimates. To the best of our knowledge, this paper is the first comprehensive study on such stochastic models used specifically with BeiDou data. Numéro de notice : A2016-424 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0896-7 En ligne : http://dx.doi.org/10.1007/s00190-016-0896-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81318 [article]

The IGS contribution to ITRF2014 / Paul Rebischung in Journal of geodesy, vol 90 n° 7 (July 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 7 (July 2016) . - pp 611 – 630 Titre : The IGS contribution to ITRF2014 Type de document : Article/Communication Auteurs : Paul Rebischung , Auteur ; Zuheir Altamimi , Auteur ; Jim Ray, Auteur ; Bruno Garayt , Auteur Année de publication : 2016 Article en page(s) : pp 611 – 630 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] données GNSS [Termes IGN] estimation de précision [Termes IGN] géocentre [Termes IGN] International Terrestrial Reference Frame [Termes IGN] réseau géodésique terrestre Résumé : (auteur) Following the first reprocessing campaign performed by the International GNSS Service (IGS) in 2008, a second reprocessing campaign (repro2) was finalized in 2015. Nine different Analysis Centers (ACs) reanalyzed the history of GNSS data collected by a global tracking network back to 1994 using the latest available models and methodology, and provided daily terrestrial frame solutions among other products. Daily combinations of the AC terrestrial frame solutions provided the IGS input to the next release of the International Terrestrial Reference Frame (ITRF2014). From weighted root mean squares values of the residuals of the daily repro2 combinations, the overall inter-AC level of agreement is assessed to be 1.5 mm for the horizontal components and 4 mm for the vertical component of station positions, 25–40 μas for pole coordinates, 140–200 μas/day for pole rates, 8–20 μs/day for calibrated length-of-day estimates, 4 mm for the X and Y components of geocenter motion, 8 mm for its Z component and 0.5 mm for the terrestrial scale. On the long term, the origins (resp. scales) of the AC terrestrial frames show relative offsets and rates within ±3 mm and ±0.3 mm/year (resp. ±0.5 mm and ±0.05 mm/year). The combination residuals also present AC-specific features, some of which are explained by known analysis specifics, while others remain under investigation. Numéro de notice : A2016-425 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0897-6 Date de publication en ligne : 08/04/2016 En ligne : http://dx.doi.org/10.1007/s00190-016-0897-6 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81319 [article]

IVS contribution to ITRF2014 / Sabine Bachmann in Journal of geodesy, vol 90 n° 7 (July 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 7 (July 2016) . - pp 631 – 654 Titre : IVS contribution to ITRF2014 Type de document : Article/Communication Auteurs : Sabine Bachmann, Auteur ; Daniela Thaller, Auteur ; Ole Roggenbuck, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 631 – 654 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] coordonnées géodésiques [Termes IGN] International Terrestrial Reference System [Termes IGN] précision des données [Termes IGN] station de référence [Termes IGN] station permanente [Termes IGN] station VLBI Résumé : (auteur) Every few years the International Terrestrial Reference System (ITRS) Center of the International Earth Rotation and Reference Systems Service (IERS) decides to generate a new version of the International Terrestrial Reference Frame (ITRF). For the upcoming ITRF2014 the official contribution of the International VLBI Service for Geodesy and Astrometry (IVS) comprises 5796 combined sessions in SINEX file format from 1979.6 to 2015.0 containing 158 stations, overall. Nine AC contributions were included in the combination process, using five different software packages. Station coordinate time series of the combined solution show an overall repeatability of 3.3 mm for the north, 4.3 mm for the east and 7.5 mm for the height component over all stations. The minimum repeatabilities are 1.5 mm for north, 2.1 mm for east and 2.9 mm for height. One of the important differences between the IVS contribution to the ITRF2014 and the routine IVS combination is the omission of the correction for non-tidal atmospheric pressure loading (NTAL). Comparisons between the amplitudes of the annual signals derived by the VLBI observations and the annual signals from an NTAL model show that for some stations, NTAL has a high impact on station height variation. For other stations, the effect of NTAL is low. Occasionally other loading effects have a higher influence (e.g. continental water storage loading). External comparisons of the scale parameter between the VTRF2014 (a TRF based on combined VLBI solutions), DTRF2008 (DGFI-TUM realization of ITRS) and ITRF2008 revealed a significant difference in the scale. A scale difference of 0.11 ppb (i.e. 0.7 mm on the Earth’s surface) has been detected between the VTRF2014 and the DTRF2008, and a scale difference of 0.44 ppb (i.e. 2.8 mm on the Earth’s surface) between the VTRF2014 and ITRF2008. Internal comparisons between the EOP of the combined solution and the individual solutions from the AC contributions show a WRMS in X- and Y-Pole between 40 and 100 μas and for dUT1 between 5 and 15 μs. External comparisons with respect to the IERS-08-C04 series show a WRMS of 132 and 143 μas for X- and Y-Pole, respectively, and 13 μs for dUT. Numéro de notice : A2016-426 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0899-4 En ligne : http://dx.doi.org/10.1007/s00190-016-0899-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81320 [article]

Fast computation of general forward gravitation problems / Fabien Casenave in Journal of geodesy, vol 90 n° 7 (July 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 7 (July 2016) . - pp 655 – 675 Titre : Fast computation of general forward gravitation problems Type de document : Article/Communication Auteurs : Fabien Casenave , Auteur ; Laurent Métivier , Auteur ; Gwendoline Pajot-Métivier , Auteur ; Isabelle Panet , Auteur Année de publication : 2016 Article en page(s) : pp 655 – 675 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] France (géographie physique) [Termes IGN] masse de la Terre [Termes IGN] potentiel de pesanteur terrestre [Termes IGN] vitesse Résumé : (auteur) We consider the well-known problem of the forward computation of the gradient of the gravitational potential generated by a mass density distribution of general 3D geometry. Many methods have been developed for given geometries, and the computation time often appears as a limiting practical issue for considering large or complex problems. In this work, we develop a fast method to carry out this computation, where a tetrahedral mesh is used to model the mass density distribution. Depending on the close- or long-range nature of the involved interactions, the algorithm automatically switches between analytic integration formulae and numerical quadratic formulae, and relies on the Fast Multipole Method to drastically increase the computation speed of the long-range interactions. The parameters of the algorithm are empirically chosen for the computations to be the fastest possible while guarantying a given relative accuracy of the result. Computations that would load many-core clusters for days can now be carried out on a desk computer in minutes. The computation of the contribution of topographical masses to the Earth’s gravitational field at the altitude of the GOCE satellite and over France are proposed as numerical illustrations of the method. Numéro de notice : A2016-427 Affiliation des auteurs : LASTIG LAREG (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0900-2 Date de publication en ligne : 08/04/2016 En ligne : http://dx.doi.org/ 10.1007/s00190-016-0900-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81321 [article]