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Termes IGN > sciences naturelles > sciences de la Terre et de l'univers > géosciences > géophysique interne > géodésie > géodésie spatiale > interférométrie
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ITRF2005: A new release of the International Terrestrial Reference Frame based on time series of station positions and Earth Orientation Parameters / Zuheir Altamimi in Journal of geophysical research : Solid Earth, vol 112 n° 9 (September 2007)
[article]
Titre : ITRF2005: A new release of the International Terrestrial Reference Frame based on time series of station positions and Earth Orientation Parameters Type de document : Article/Communication Auteurs : Zuheir Altamimi , Auteur ; Xavier Collilieux , Auteur ; J. Legrand, Auteur ; Bruno Garayt , Auteur ; Claude Boucher , Auteur Année de publication : 2007 Article en page(s) : pp B09401 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] interférométrie à très grande base
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] orientation de la TerreRésumé : (auteur) Unlike the past International Terrestrial Reference Frame (ITRF) versions where global long-term solutions were combined, the ITRF2005 uses as input data time series (weekly from satellite techniques and 24-h session-wise from Very Long Baseline Interferometry) of station positions and daily Earth Orientation Parameters (EOPs). The advantage of using time series of station positions is that it allows to monitor station non-linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters, namely the origin and the scale. The ITRF2005 origin is defined in such a way that it has zero translations and translation rates with respect to the Earth center of mass, averaged by the Satellite Laser Ranging (SLR) time series spanning 13 years of observations. Its scale is defined by nullifying the scale and its rate with respect to the Very Long Baseline Interferometry (VLBI) time series spanning 26 years of observations. The ITRF2005 orientation (at epoch 2000.0) and its rate are aligned to the ITRF2000 using 70 stations of high geodetic quality. The estimated level of consistency of the ITRF2005 origin (at epoch 2000.0) and its rate with respect to the ITRF2000 is respectively 0.1, 0.8, 5.8 mm and 0.2, 0.1, 1.8 mm/yr along the X, Y and Z-axis. We estimate the formal errors on these components to be 0.3 mm and 0.3 mm/yr. We believe that this low level of agreement between the two frame origins is most probably due to the poor SLR network geometry and its degradation over time. The ITRF2005 combination involving 84 co-location sites revealed a scale inconsistency of 1 ppb (6.3 mm at the equator), at epoch 2000.0, and 0.08 ppb/yr between the SLR and VLBI long-term solutions as obtained by the stacking of their respective time series. Possible causes of this inconsistency may include the poor SLR and VLBI networks and their co-locations, local tie uncertainties, systematic effects and possible inconsistent model corrections used in the data analysis of both techniques. For the first time of the ITRF history, the ITRF2005 rigorous combination provides self-consistent series of EOPs, including Polar Motion from VLBI and satellite techniques and Universal Time and Length of Day from VLBI only. A velocity field of 152 sites with an error less than 1.5 mm/yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the ITRF2005 frame. This new absolute plate motion model supersedes and significantly improves that of the ITRF2000 which involved six major tectonic plates. Numéro de notice : A2007-684 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article DOI : 10.1029/2007JB004949 Date de publication en ligne : 07/09/2007 En ligne : https://doi.org/10.1029/2007JB004949 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102733
in Journal of geophysical research : Solid Earth > vol 112 n° 9 (September 2007) . - pp B09401[article]Combined Earth orientation parameters based on homogeneous and continuous VLBI and GPS data / Daniela Thaller in Journal of geodesy, vol 81 n° 6-8 (June - August 2007)
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Titre : Combined Earth orientation parameters based on homogeneous and continuous VLBI and GPS data Type de document : Article/Communication Auteurs : Daniela Thaller, Auteur ; Manuela Krügel, Auteur ; Markus Rothacher, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 529 - 541 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] Bernese
[Termes IGN] données GPS
[Termes IGN] données ITGB
[Termes IGN] mouvement du pôle
[Termes IGN] nutation
[Termes IGN] point de liaison (géodésie)
[Termes IGN] rotation de la TerreRésumé : (Auteur) The CONT02 campaign is of great interest for studies combining very long baseline interferometry (VLBI) with other space-geodetic techniques, because of the continuously available VLBI observations over 2 weeks in October 2002 from a homogeneous network. Especially, the combination with the Global Positioning System (GPS) offers a broad spectrum of common parameters. We combined station coordinates, Earth orientation parameters (EOPs) and troposphere parameters consistently in one solution using technique- specific datum-free normal equation systems. In this paper, we focus on the analyses concerning the EOPs, whereas the comparison and combination of the troposphere parameters and station coordinates are covered in a companion paper in Journal of Geodesy. In order to demonstrate the potential of the VLBI and GPS space-geodetic techniques, we chose a sub-daily resolution for polar motion (PM) and universal time (UT). A consequence of this solution set-up is the presence of a one-to-one correlation between the nutation angles and a retrograde diurnal signal in PM. The Bernese GPS Software used for the combination provides a constraining approach to handle this singularity. Simulation studies involving both nutation offsets and rates helped to get a deeper understanding of this singularity. With a rigorous combination of UT1–UTC and length of day (LOD) from VLBI and GPS, we showed that such a combination works very well and does not suffer from the systematic effects present in the GPS-derived LOD values. By means of wavelet analyses and the formal errors of the estimates, we explain this important result. The same holds for the combination of nutation offsets and rates. The local geodetic ties between GPS and VLBI antennas play an essential role within the inter-technique combination. Several studies already revealed non-negligible discrepancies between the terrestrial measurements and the space-geodetic solutions. We demonstrate to what extent these discrepancies propagate into the combined EOP solution. Copyright Springer Numéro de notice : A2007-243 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0115-z En ligne : https://doi.org/10.1007/s00190-006-0115-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28606
in Journal of geodesy > vol 81 n° 6-8 (June - August 2007) . - pp 529 - 541[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07062 RAB Revue Centre de documentation En réserve L003 Disponible 266-07061 RAB Revue Centre de documentation En réserve L003 Disponible Indirect approach to invariant point determination for SLR and VLBI systems: an assessment / John Dawson in Journal of geodesy, vol 81 n° 6-8 (June - August 2007)
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Titre : Indirect approach to invariant point determination for SLR and VLBI systems: an assessment Type de document : Article/Communication Auteurs : John Dawson, Auteur ; Pierguido Sarti, Auteur ; G.M. Johnston, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 433 - 441 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] erreur systématique
[Termes IGN] interférométrie à très grande base
[Termes IGN] invariant
[Termes IGN] point de liaison (géodésie)
[Termes IGN] télémétrie laser sur satelliteRésumé : (Auteur) We assess the accuracy of some indirect approaches to invariant point (IVP), or system reference point, determination of satellite laser ranging (SLR) and very long baseline interferometry (VLBI) systems using both observed and simulated survey data sets. Indirect IVP determination involves the observation of targets located on these systems during specific rotational sequences and by application of geometrical models that describe the target motion during these sequences. Of concern is that most SLR and VLBI systems have limited rotational freedom thereby placing constraint on the reliability of parameter estimation, including the IVP position. We assess two current approaches to IVP analysis using survey data observed at the Yarragadee (Australia) SLR and the Medicina (Italy) VLBI sites and also simulated data of a large rotationally constrained (azimuth-elevation) VLBI system. To improve reliability we introduce and assess some new geometric conditions, including inter-axis, inter-circle and inter-target conditions, to existing IVP analysis strategies. The error component of a local tie specifically associated with the indirect determination of SLR and VLBI IVP is less than 0.5 mm. For systems with significant rotational limits we find that the inter-axis and inter-circle conditions are critical to the computation of unbiased IVP coordinates at the sub-millimetre level. When the inter-axis and inter-circle geometric conditions are not imposed, we retrieve biased vertical coordinates of the IVP (in our simulated VLBI system) in the range of 1.2–3.4 mm. Using the new geometric conditions we also find that the axis-offset estimates can be recovered at the sub- millimetre accuracy (0.5 mm). Copyright Springer Numéro de notice : A2007-241 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0125-x En ligne : https://doi.org/10.1007/s00190-006-0125-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28604
in Journal of geodesy > vol 81 n° 6-8 (June - August 2007) . - pp 433 - 441[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07062 RAB Revue Centre de documentation En réserve L003 Disponible 266-07061 RAB Revue Centre de documentation En réserve L003 Disponible The impact of radio source structure on European geodetic VLBI measurements / V. Tornatore in Journal of geodesy, vol 81 n° 6-8 (June - August 2007)
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Titre : The impact of radio source structure on European geodetic VLBI measurements Type de document : Article/Communication Auteurs : V. Tornatore, Auteur ; Patrick Charlot, Auteur Année de publication : 2007 Article en page(s) : pp 469 - 478 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] données ITGB
[Termes IGN] European VLBI network
[Termes IGN] interférométrie à très grande base
[Termes IGN] rayonnement cosmiqueRésumé : (Auteur) European geodetic very long baseline interferometry (VLBI) sessions (also known as EUROPE sessions) have been carried out on a regular basis for the past 15 years to study relative crustal motions within Europe. These sessions are based on observations of extragalactic radio sources, which serve as distant fiducial marks to establish an accurate and stable celestial reference frame for long-term geodetic measurements. The radio sources, however, are not always point-like on milliarcsecond scales, as VLBI imaging has revealed. In this work, we quantify the magnitude of the expected effect of intrinsic source structure on geodetic bandwidth synthesis delay VLBI measurements for a subset of 14 sources regularly observed during the EUROPE sessions. These sources have been imaged at both X-band (8.4 GHz) and S-band (2.3 GHz) based on dedicated observations acquired with the European VLBI Network (EVN) in November 1996. The results of this calculation indicate that the reference source 0457+024 causes significant structural effects in measurements obtained on European VLBI baselines (about 10 picoseconds on average), whereas most of the other sources produce effects that are only occasionally larger than a few picoseconds. Applying the derived source structure models to the data of the EUROPE5-96 session carried out at the same epoch as the EVN experiment shows no noticeable changes in the estimated VLBI station locations. Copyright Springer Numéro de notice : A2007-242 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0146-0 En ligne : https://doi.org/10.1007/s00190-007-0146-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28605
in Journal of geodesy > vol 81 n° 6-8 (June - August 2007) . - pp 469 - 478[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07062 RAB Revue Centre de documentation En réserve L003 Disponible 266-07061 RAB Revue Centre de documentation En réserve L003 Disponible A comparison of GPS, VLBI and model estimates of ocean tide loading displacements / I.D. Thomas in Journal of geodesy, vol 81 n° 5 (May 2007)
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Titre : A comparison of GPS, VLBI and model estimates of ocean tide loading displacements Type de document : Article/Communication Auteurs : I.D. Thomas, Auteur ; Matt A. King, Auteur ; Peter J. Clarke, Auteur Année de publication : 2007 Article en page(s) : pp 359 - 368 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] analyse comparative
[Termes IGN] interférométrie à très grande base
[Termes IGN] positionnement par GPS
[Termes IGN] positionnement par ITGB
[Termes IGN] surcharge océaniqueRésumé : (Auteur) In recent years, ocean tide loading displacements (OTLD) have been measured using the Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI). This study assesses the accuracy of GPS measurements of OTLD by comparison with VLBI measurements and estimates derived from numerical ocean tide models. A daily precise point positioning (PPP) analysis was carried out on ?11 years of GPS data for each of 25 sites that have previous OTLD estimates based on data from co-located VLBI sites. Ambiguities were fixed to integer values where possible. The resulting daily estimates of OTLD, at eight principal diurnal and semi-diurnal tidal frequencies, were combined to give GPS measurements of OTLD at each site. The 3D GPS and VLBI measurements of OTLD were compared with estimates computed (by convolution with Green’s functions) from five modern ocean tide models (CSR4.0, FES2004, GOT00.2, NAO99b and TPXO6.2). The GPS/model agreement is shown to be similar to the VLBI/model agreement. In the important radial direction, the GPS/model misfit is shown to be smaller than the VLBI/model misfit for seven of the eight tidal constituents; the exception being the K2 constituent. Fixing of GPS carrier-phase ambiguities to integer values resulted in a marginal improvement to the GPS/model agreement. Statistically, it is shown there is no significance to the difference between the fit of the GPS and VLBI measurements of OTLD to modelled values. Equally, differences in fit of either the complete set of GPS or VLBI estimates to the five sets of model-derived values cannot be identified with statistical significance. It is thus concluded that, overall, we cannot distinguish between GPS and VLBI measurements of OTLD, and that at the global scale, present ocean tide models are accurate to within the current measurement noise of these techniques. Copyright Springer Numéro de notice : A2007-125 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0118-9 En ligne : https://doi.org/10.1007/s00190-006-0118-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28488
in Journal of geodesy > vol 81 n° 5 (May 2007) . - pp 359 - 368[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07051 RAB Revue Centre de documentation En réserve L003 Disponible 266-07052 RAB Revue Centre de documentation En réserve L003 Disponible PermalinkProccedings of the 18th European VLBI for geodesy and astrometry working meeting, Vienna, 12-13 April 2007 / Johannes Böhm (2007)PermalinkSpace geodetic techniques and the canadian spatial reference system evolution, status and possibilities / Pierre Héroux in Geomatica, vol 60 n° 2 (June 2006)PermalinkPermalinkPermalinkPermalinkReport on the Symposium of the IAG Subcommission for Europe (EUREF) held in Riga, 14 - 17 June 2006 & reports of the EUREF technical working group, EUREF publication n° 16 / Joao Agria Torres (2006)PermalinkReport on the symposium of the IAG Subcommission for Europe (EUREF) held in Vienna, 1 - 4 June 2005 & reports of the EUREF technical working group, EUREF publication n° 15 / Joao Agria Torres (2006)PermalinkPermalinkIs there utility in rigorous combinations of VLBI and GPS Earth orientation parameters? / Jim Ray in Journal of geodesy, vol 79 n° 9 (December 2005)Permalink