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Fiducial reference systems for time and coordinates in satellite altimetry / Stelios Mertikas in Advances in space research, vol 68 n° 2 (15 July 2021)  

Public [article]  inAdvances in space research > vol 68 n° 2 (15 July 2021) . - pp 1140 - 1160 Titre : Fiducial reference systems for time and coordinates in satellite altimetry Type de document : Article/Communication Auteurs : Stelios Mertikas, Auteur ; Craig Donlon, Auteur ; Demetrios Matsakis, Auteur ; Constantin Mavrocordatos, Auteur ; Zuheir Altamimi , Auteur ; Costas Kokolakis, Auteur ; Achilles Tripolitsiotis, Auteur Année de publication : 2021 Projets : 3-projet - voir note / Article en page(s) : pp 1140 - 1160 Note générale : bibliographie Part of this work has been produced with the financial assistance of the European Union and the European Space Agency under the project FRM4S6 (Fiducial Reference Systems For Sentinel-6, No. 4000129892/20/NL/FF/ab) Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] altimétrie satellitaire par radar [Termes IGN] coordonnées cartésiennes géocentriques [Termes IGN] système de référence altimétrique Résumé : (auteur) Time is the fundamental measurement in satellite altimetry and the key parameter in building and keeping up a long-term, consistent, and reliable record for monitoring changes in sea level. Over the years, different time scales, although interconnected, have been used in altimetry and also in satellite positioning. This sometimes leads to inexplicit descriptions and ambiguous use of time and orbit coordinates as well as of their transformations between various reference and measuring systems. Altimetry satellites, like Sentinel-3, CryoSat-2, Jason-3, HY-2A/-2B, IceSat-2, etc., observe and practically realize ranges by measuring time differences between the transmission and reception of an electromagnetic wave (either radar or laser at present). Similar principles apply for global navigation satellite systems and for their terrestrial reference systems upon which altimetry is linked and tied together. Yet, the “meter” of any terrestrial reference systems is also defined by time. This work seeks to establish a standard reference system for “time” and “coordinates” in an effort to reach uniform and absolute standardization for satellite altimetry. It describes various errors generated from differences, discontinuities and interactions in time, frequency, range, time tagging, and reference coordinate frames. A new approach, called “fiducial reference measurements for altimetry”, is here given to examine ways to connect errors with metrology standards in order to improve the estimation of uncertainty budgets in ocean and water level observation by altimetry. Finally, the geocentric inertial reference system and the international atomic time are proposed in this paper for satellite altimetry observations and products. Numéro de notice : A2021-601 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2020.05.014 En ligne : https://doi.org/10.1016/j.asr.2020.05.014 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98240 [article]

IX Hotine-Marussi Symposium on Mathematical Geodesy. Review of reference frame representations for a deformable Earth / Zuheir Altamimi (2021)  

Public Titre de série : IX Hotine-Marussi Symposium on Mathematical Geodesy Titre : Review of reference frame representations for a deformable Earth Type de document : Chapitre/Contribution Auteurs : Zuheir Altamimi , Auteur ; Paul Rebischung , Auteur ; Xavier Collilieux , Auteur ; Laurent Métivier , Auteur ; Kristel Chanard , Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2021 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 151 Projets : 2-Pas d'info accessible - article non ouvert / Conférence : IAG 2018, 9th Hotine-Marussi Symposium on Mathematical Geodesy 18/06/2018 22/06/2018 Rome Italie Proceedings Springer Importance : pp 51 - 56 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] coordonnées GPS [Termes IGN] erreur systématique [Termes IGN] International Terrestrial Reference Frame [Termes IGN] série temporelle Résumé : (auteur) Our planet Earth is constantly deforming under the effects of geophysical processes that cause linear and nonlinear displacements of the geodetic stations upon which the International Terrestrial Reference Frame (ITRF) is established. The ITRF has traditionally been defined as a secular (linear) frame in which station coordinates are described by piecewise linear functions of time. Nowadays, some particularly demanding applications however require more elaborate reference frame representations that can accommodate non-linear displacements of the reference stations. Two such types of reference frame representations are reviewed: the usual linear frame enhanced with additional parametric functions such as seasonal sine waves, and non-parametric time series of quasi-instantaneous reference frames. After introducing those two reference frame representations, we briefly review the systematic errors present in geodetic station position time series. We finally discuss the practical issues raised by the existence of these systematic errors for the implementation of both types of non-linear reference frames. Numéro de notice : H2021- Affiliation des auteurs : Géodésie (mi2018-2019) Thématique : POSITIONNEMENT Nature : Chapître / contribution nature-HAL : ChOuvrScient DOI : 10.1007/1345_2019_66 date de publication en ligne : 17/05/2019 En ligne : https://doi.org/10.1007/1345_2019_66 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95512

Past and present ITRF solutions from geophysical perspectives / Laurent Métivier in Advances in space research, vol 65 n° 12 (15 June 2020)  

Public [article]  inAdvances in space research > vol 65 n° 12 (15 June 2020) . - pp 2711 - 2722 Titre : Past and present ITRF solutions from geophysical perspectives Type de document : Article/Communication Auteurs : Laurent Métivier , Auteur ; Zuheir Altamimi , Auteur ; Hélène Rouby , Auteur Année de publication : 2020 Projets : TOSCA / Article en page(s) : pp 2711 - 2722 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] ajustement glacio-isostatique [Termes IGN] champ de vitesse [Termes IGN] fonte des glaces [Termes IGN] International Terrestrial Reference Frame [Termes IGN] positionnement par GNSS [Termes IGN] vitesse Résumé : (auteur) Questions about the accuracy of the origin of the different versions of International Terrestrial Reference Frame (ITRF), have been regularly raised. In particular the origin drift between ITRF2000 and ITRF2005 (and subsequent ITRF solutions) is well-known to be problematic. Here, we look forward a sort of geophysical evaluation of ITRF solutions. We investigate GNSS vertical velocities provided by the last four ITRF solutions (ITRF2000 to ITRF2014; Altamimi et al., 2005, 2007, 2011, 2016) that we compare with different Global Isostatic Adjustment (GIA) model predictions. We find that each new ITRF solution appears to be more and more consistent with all GIA predictions, except ITRF2014 whose consistency with the GIA models depends on the date of observation. Indeed, GNSS observations and GIA predictions appear consistent at global scale at a level of ~4 mm/yr using ITRF2000 data, ~2.5–3 mm/yr using ITRF2005 data, and ~2 mm/yr using ITRF2008 data (global weighted root mean squares). For ITRF2014, the consistency between GNSS observations and GIA predictions is extremely high in 2000 (~1.5 mm/yr) but seems then to decrease with time (~2 mm/yr in 2013). This discrepancy is due to the recent ice melting effect that is not accounted for in GIA models, but clearly evidenced by ITRF2014 vertical velocities during the last years of observations, in particular in Greenland. Numéro de notice : A2020-364 Affiliation des auteurs : UMR IPGP-Géod (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2020.03.031 date de publication en ligne : 06/04/2020 En ligne : https://doi.org/10.1016/j.asr.2020.03.031 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96828 [article]

Accounting for spatiotemporal correlations of GNSS coordinate time series to estimate station velocities / Clément Benoist in Journal of geodynamics, vol 135 (April 2020)  

Public [article]  inJournal of geodynamics > vol 135 (April 2020) . - n° 101693 Titre : Accounting for spatiotemporal correlations of GNSS coordinate time series to estimate station velocities Type de document : Article/Communication Auteurs : Clément Benoist , Auteur ; Xavier Collilieux , Auteur ; Paul Rebischung , Auteur ; Zuheir Altamimi , Auteur ; Olivier Jamet , Auteur ; Laurent Métivier , Auteur ; Kristel Chanard , Auteur ; Liliane Bel, Auteur Année de publication : 2020 Projets : GEODESIE / Coulot, David, Université de Paris / Clerici, Christine Article en page(s) : n° 101693 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] corrélation [Termes IGN] covariance [Termes IGN] données spatiotemporelles [Termes IGN] repère de référence terrestre conventionnel [Termes IGN] série temporelle [Termes IGN] vitesse Résumé : (auteur) It is well known that GNSS permanent station coordinate time series exhibit time-correlated noise. Spatial correlations between coordinate time series of nearby stations are also long-established and generally handled by means of spatial filtering techniques. Accounting for both the temporal and spatial correlations of the noise via a spatiotemporal covariance model is however not yet a common practice. We demonstrate in this paper the interest of using such a spatiotemporal covariance model of the stochastic variations in GNSS time series in order to estimate long-term station coordinates and especially velocities. We provide a methodology to rigorously assess the covariances between horizontal coordinate variations and use it to derive a simple exponential spatiotemporal covariance model for the stochastic variations in the IGS repro2 station coordinate time series. We then use this model to estimate station velocities for two selected datasets of 10 time series in Europe and 11 time series in the USA. We show that coordinate prediction as well as velocity determination from short time series are improved when using this spatiotemporal model, as compared with the case where spatiotemporal correlations are ignored. Numéro de notice : A2020-460 Affiliation des auteurs : Géodésie+Ext (mi2018-2019) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jog.2020.101693 date de publication en ligne : 13/01/2020 En ligne : https://doi.org/10.1016/j.jog.2020.101693 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95385 [article]

Assessment of geocenter motion estimates from the IGS second reprocessing / Yifang Ma in GPS solutions, vol 24 n° 2 (April 2020)  

Public [article]  inGPS solutions > vol 24 n° 2 (April 2020) . - n° 55 Titre : Assessment of geocenter motion estimates from the IGS second reprocessing Type de document : Article/Communication Auteurs : Yifang Ma , Auteur ; Paul Rebischung , Auteur ; Zuheir Altamimi , Auteur ; Weiping Jiang, Auteur Année de publication : 2020 Projets : 3-projet - voir note / Clerici, Christine Article en page(s) : n° 55 Note générale : bibliographie This study is supported by the National Science Fund for Distinguished Young Scholars (No. 41525014) and the National Key R&D Program of China (No. 2018YFC15036). Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] analyse comparative [Termes IGN] données TLS (télémétrie) [Termes IGN] International Terrestrial Reference Frame [Termes IGN] mouvement du géocentre [Termes IGN] série temporelle [Termes IGN] variation saisonnière [Termes IGN] variation temporelle Résumé : (auteur) We investigate geocenter motion time series derived from the combined solutions and six individual analysis center (AC) solutions of the International GNSS Service (IGS) second reprocessing campaign using the network shift approach, in terms of noise content, long-term trends, periodic and aperiodic variations. We assess these GNSS geocenter motion estimates by comparison with independent estimates from satellite laser ranging (SLR). The GNSS geocenter time series exhibit correlated noise which is better represented by a white plus power–law noise model in the X and Y directions, and by a white plus first-order autoregressive (or generalized Gauss–Markov) noise model in the Z direction. The GNSS geocenter time series include expected seasonal variations, but also spurious draconitic signals, particularly in the Z direction. GNSS annual geocenter motion estimates are in reasonable agreement with SLR estimates in the X and Y directions. In the Z direction, however, the annual signals derived from the IGS solutions disagree with SLR estimates, except for three particular ACs. This suggests that the different orbit modeling strategies used by these ACs may constitute an improvement over the conventional strategy employed by the other ACs. The background noise in GNSS and SLR geocenter time series finally appears to be correlated, suggesting that it might partly reflect real, aperiodic geocenter motion. Numéro de notice : A2020-838 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-0968-2 date de publication en ligne : 10/03/2020 En ligne : https://doi.org/10.1007/s10291-020-0968-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98264 [article]

Comparative analysis of different atmospheric surface pressure models and their impacts on daily ITRF2014 GNSS residual time series / Zhao Li in Journal of geodesy, vol 94 n°4 (April 2020)  

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ITRF2014, Earth figure changes, and geocenter velocity: Implications for GIA and recent ice melting / Laurent Métivier in Journal of geophysical research : Solid Earth, vol 125 n° 2 (February 2020)  

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Description and evaluation of DTRF2014, JTRF2014 and ITRF2014 / Zuheir Altamimi (2020)  

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Description and evaluation of DTRF2014, JTRF2014 and ITRF2014, ch. 3. ITRS Center evaluation of DTRF2014 and JTRF2014 with respect to ITRF2014 / Zuheir Altamimi (2020)  

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Position, navigation, and timing technologies in the 21st century: Integrated satellite navigation, sensor systems, and civil applications, ch. 27. Global geodesy and reference frames / Chris Rizos (2020)  

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Review of Reference Frame Representations for a Deformable Earth / Zuheir Altamimi (2019)  

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The International Terrestrial Reference Frame: lessons from ITRF2014 / Zuheir Altamimi in Rendiconti Lincei. Scienze Fisiche e Naturali, vol 29 suppl 1 (June 2018)  

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Assessment of the possible contribution of space ties on-board GNSS satellites to the terrestrial reference frame / Sara Bruni in Journal of geodesy, vol 92 n° 4 (April 2018)  

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Bruit de scintillation dans les séries temporelles de positions GNSS / Paul Rebischung (2018) 

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Comparing non-linear geocenter motion derived from GNSS and SLR observations corrected for loading and thermoelastic deformation / Kristel Chanard (2018)

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