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The importance of co-located VLBI Intensive stations and GNSS receivers / Christopher Dieck in Journal of geodesy, vol 97 n° 3 (March 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 3 (March 2023) . - n° 21 Titre : The importance of co-located VLBI Intensive stations and GNSS receivers Type de document : Article/Communication Auteurs : Christopher Dieck, Auteur ; Megan C. Johnson, Auteur ; Daniel S. MacMillan, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 21 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] Hawaii (Etats-Unis) [Termes IGN] interférométrie à très grande base [Termes IGN] positionnement par ITGB [Termes IGN] rapport signal sur bruit [Termes IGN] récepteur GNSS [Termes IGN] station GNSS [Termes IGN] station VLBI [Termes IGN] temps universel coordonné Résumé : (auteur) Frequent, low-latency measurements of the Earth’s rotation phase, expressed as UT1−UTC critically support the current estimate and short-term prediction of this highly variable Earth orientation parameter (EOP). Very long baseline interferometry (VLBI) Intensive sessions provide the required data. However, the Intensive UT1− UTC measurement accuracy depends on the accuracy of numerous models, including the VLBI station position. Intensives observed with the Maunakea (Mk) and Pie Town (Pt) stations of the Very Long Baseline Array (VLBA) illustrate how a geologic event (i.e., the Mw 6.9 Hawai‘i Earthquake of May 4th, 2018) can cause a station displacement and an associated offset in the values of UT1−UTC measured by that baseline, rendering the data from the series useless until it is corrected. Using the nonparametric Nadaraya–Watson estimator to smooth the measured UT1−UTC values before and after the earthquake, we calculate the offset in the measurement to be 75.7 ± 4.6 μs. Analysis of the sensitivity of the Mk-Pt baseline’s UT1−UTC measurement to station position changes shows that the measured offset is consistent with the 67.2 ± 5.9 μs expected offset based on the 12.4 ± 0.6 mm total coseismic displacement of the Maunakea VLBA station determined from the displacement of the co-located global navigation satellite system (GNSS) station. GNSS station position information is known with a latency on the order of tens of hours and thus can be used to correct the a priori position model of a co-located VLBI station such that it can continue to provide accurate measurements of the critical EOP UT1−UTC as part of Intensive sessions. In the absence of a co-located GNSS receiver, the VLBI station position model would likely not be updated for several months, and a near real-time correction would not be possible. This contrast highlights the benefit of co-located GNSS and VLBI stations in support of the monitoring of UT1−UTC with single-baseline Intensives. Numéro de notice : A2023-133 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01690-1 Date de publication en ligne : 03/03/2023 En ligne : https://doi.org/10.1007/s00190-022-01690-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102678 [article]

Continental hydrology loading observed by VLBI measurements / David Eriksson in Journal of geodesy, vol 88 n° 7 (July 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 7 (July 2014) . - pp 675 - 690 Titre : Continental hydrology loading observed by VLBI measurements Type de document : Article/Communication Auteurs : David Eriksson, Auteur ; Daniel S. MacMillan, Auteur Année de publication : 2014 Article en page(s) : pp 675 - 690 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] déformation de la croute terrestre [Termes IGN] données GRACE [Termes IGN] données ITGB [Termes IGN] effet de charge [Termes IGN] modèle hydrographique Résumé : (Auteur) Variations in continental water storage lead to loading deformation of the crust with typical peak-to-peak variations at very long baseline interferometry (VLBI) sites of 3–15 mm in the vertical component and 1–2 mm in the horizontal component. The hydrology signal at VLBI sites has annual and semi-annual components and clear interannual variations. We have calculated the hydrology loading series using mass loading distributions derived from the global land data assimilation system (GLDAS) hydrology model and alternatively from a global grid of equal-area gravity recovery and climate experiment (GRACE) mascons. In the analysis of the two weekly VLBI 24-h R1 and R4 network sessions from 2003 to 2010 the baseline length repeatabilities are reduced in 79 % (80 %) of baselines when GLDAS (GRACE) loading corrections are applied. Site vertical coordinate repeatabilities are reduced in about 80 % of the sites when either GLDAS or GRACE loading is used. In the horizontal components, reduction occurs in 70–80 % of the sites. Estimates of the annual site vertical amplitudes were reduced for 16 out of 18 sites if either loading series was applied. We estimated loading admittance factors for each site and found that the average admittances were 1.01 ± 0.05 for GRACE and 1.39 ± 0.07 for GLDAS. The standard deviations of the GRACE admittances and GLDAS admittances were 0.31 and 0.68, respectively. For sites that have been observed in a set of sufficiently temporally dense daily sessions, the average correlation between VLBI vertical monthly averaged series and GLDAS or GRACE loading series was 0.47 and 0.43, respectively. Numéro de notice : A2014-414 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0713-0 Date de publication en ligne : 19/04/2014 En ligne : https://doi.org/10.1007/s00190-014-0713-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=73954 [article]

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External evaluation of the Terrestrial Reference Frame: report of the task force of the IAG sub-commission 1.2 / Xavier Collilieux (2014)  

Public contenu dans Earth on the Edge: Science for a Sustainable Planet / Chris Rizos (2014)   Titre : External evaluation of the Terrestrial Reference Frame: report of the task force of the IAG sub-commission 1.2 Type de document : Article/Communication Auteurs : Xavier Collilieux , Auteur ; Zuheir Altamimi , Auteur ; Donald F. Argus, Auteur ; Claude Boucher , Auteur ; Athanasios Dermanis, Auteur ; Bruce J. Haines, Auteur ; T.A. Herring, Auteur ; C. Kreemer, Auteur ; Franck G. Lemoine, Auteur ; C. Ma, Auteur ; Daniel S. MacMillan, Auteur ; J. Makinen, Auteur ; Laurent Métivier , Auteur ; J.C. Ries, Auteur ; Felix Norman Teferle, Auteur ; X. Wu, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2014 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 139 Conférence : IAG 2011, General Assembly 28/06/2011 02/07/2011 Melbourne Australie Proceedings Springer Importance : pp 197 - 202 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] International Terrestrial Reference Frame Résumé : (auteur) Ideally, the origin of the Terrestrial Reference Frame (TRF) is defined as the center of mass of the whole Earth system, the time evolution of its orientation is such that no global net rotation of the whole Earth’s surface is possible and the TRF scale is specified through the adoption of some physical constants and time-scale. These parameters need to be accurately determined since their choice has an influence on many Earth’s science applications. The aim of the task force “External evaluation of the Terrestrial Reference Frame” is to review all the applications for which the TRF accuracy is of fundamental importance. As the TRF choice has an influence on the interpretation of the results in these specific applications, we investigate if some evaluation procedures could be established. We classified the methods that allow evaluation of the TRF using ground, geodetic data or models that have not been used in the TRF construction, based on their expected contributions. Some of these methods have been applied to the latest International Terrestrial Reference System realizations and the results are presented here. Although further analysis will be necessary to deliver a more precise error budget, our findings demonstrate that the most recent realizations of the ITRS are more accurate than the previous in terms of origin and scale rate definition. The current level of ITRF2008 accuracy is likely to be at the level of 0.5 mm/year along each origin component and better than 0.3 mm/year in the scale rate according to the most recent studies. Numéro de notice : C2011-026 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-37222-3_25 Date de publication en ligne : 06/10/2013 En ligne : http://dx.doi.org/10.1007/978-3-642-37222-3_25 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=78509

Quantifying the correlation between the MEI and LOD variations by decomposing LOD with singular spectrum analysis / Karine Le Bail (2014)  

Public contenu dans Earth on the Edge: Science for a Sustainable Planet / Chris Rizos (2014)   Titre : Quantifying the correlation between the MEI and LOD variations by decomposing LOD with singular spectrum analysis Type de document : Article/Communication Auteurs : Karine Le Bail , Auteur ; John M. Gibson, Auteur ; Daniel S. MacMillan, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2014 Conférence : IAG 2011, General Assembly 28/06/2011 02/07/2011 Melbourne Australie Proceedings Springer Importance : pp 473 - 481 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse de spectre singulier [Termes IGN] données ITGB [Termes IGN] interférométrie à très grande base [Termes IGN] positionnement par ITGB [Termes IGN] série temporelle [Termes IGN] variation temporelle Résumé : (auteur) Variations in the temporal length-of-day (LOD) contain information on phenomena related to the continuous evolution of Earth processes: tidal energy dissipation and core-mantle coupling (decadal, secular), meteorological and solar-lunar tide effects (annual, semi-annual). In this work, we studied an LOD time series obtained from VLBI measurements and extracted its principal components using the Singular Spectrum Analysis (SSA). After removing the long-term trend which explains 73. 8% of the signal, three remaining components explain a further 22. 0% of the signal: an annual and a semi-annual signals as well as a second trend. We compared the Multivariate ENSO index (MEI) with the variations in the amplitudes of the annual and semi-annual components and with the second trend. The correlations are significant: 0. 58 for the annual component, − 0. 48 for the semi-annual component and 0. 46 for the second trend. Numéro de notice : C2011-028 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-37222-3_63 Date de publication en ligne : 06/10/2013 En ligne : http://dx.doi.org/10.1007/978-3-642-37222-3_63 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80597

The kinematics of Ny-Ålesund from space geodetic data / Halfdan Pascal Kierulf in Journal of geodynamics, vol 48 n° 1 (July 2009)  

Public [article]  inJournal of geodynamics > vol 48 n° 1 (July 2009) . - pp 37 - 46 Titre : The kinematics of Ny-Ålesund from space geodetic data Type de document : Article/Communication Auteurs : Halfdan Pascal Kierulf, Auteur ; Bjørn Ragnvald Pettersen, Auteur ; Daniel S. MacMillan, Auteur ; Pascal Willis , Auteur Année de publication : 2009 Article en page(s) : pp 37 - 46 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] marégraphe [Termes IGN] positionnement par DORIS [Termes IGN] positionnement par GPS [Termes IGN] positionnement par ITGB [Termes IGN] repère de référence [Termes IGN] Spitzberg [Termes IGN] station permanente Résumé : (auteur) We have compared coordinate time series from several space geodetic observing techniques to derive the kinematical motions of Ny-Ålesund, Svalbard. Velocity estimates from VLBI, GPS, and DORIS scatter more than the expected error estimates from each technique, and also between individual GPS solutions with different software and analysis strategies. A statistical combination yields average topocentric velocity components of mm/year (north), mm/year (east), and mm/year (vertical) for 1993–2007. The horizontal velocity is in agreement with a combined prediction of NUVEL-NNR-1A and the effects of post-glacial rebound and present day ice melt of nearby glaciers. The observed uplift is twice that predicted by the two latter processes. The non-linear time series of both VLBI and GPS data suggest that the uplift rate increases from 7.0 mm/year before 2003 to 10.8 mm/year after 2003. We conclude that this has a geophysical origin since no monument motions have been detected. A recent sea level decrease (1993–2007) of mm/year supports an absolute sea level increase of 3.2 mm/year as determined elsewhere by satellite altimetry. Numéro de notice : A2009-550 Affiliation des auteurs : IGN+Ext (1940-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jog.2009.05.002 Date de publication en ligne : 14/05/2009 En ligne : https://doi.org/10.1016/j.jog.2009.05.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89890 [article]