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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)
[article]
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]Exemplaires(2)
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 Toward a direct combination of space-geodetic techniques at the measurement level: Methodology and main issues / David Coulot in Journal of geophysical research : Solid Earth, vol 112 n° B5 (May 2007)
[article]
Titre : Toward a direct combination of space-geodetic techniques at the measurement level: Methodology and main issues Type de document : Article/Communication Auteurs : David Coulot , Auteur ; Philippe Berio, Auteur ; Richard Biancale, Auteur ; Sylvain Loyer, Auteur ; Laurent Soudarin, Auteur ; Anne-Marie Gontier, Auteur Année de publication : 2007 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] analyse comparative
[Termes IGN] erreur systématique inter-systèmes
[Termes IGN] positionnement par DORIS
[Termes IGN] positionnement par GNSS
[Termes IGN] positionnement par ITGB
[Termes IGN] positionnement par télémétrie laser sur satelliteRésumé : (auteur) In the framework of the activities of the Combination Research Centers (CRC) of the International Earth Rotation and Reference Systems Service (IERS), the French Groupe de Recherche en Géodésie Spatiale (GRGS) studies the benefit of combining space-geodetic techniques (Doppler orbitography and radiopositioning integrated by satellite, GPS, satellite laser ranging, and very long baseline interferometry) at the observational level. This combination aims to produce a global and consistent solution for Earth orientation parameters (EOPs), polar motion xp and yp, and universal time UT1 with a 1-day or a 6-hour sampling, as well as weekly station positions. In this paper we present a methodology for multitechnique combination at the observational level. We process the measurements of the four techniques over a 1-year period (the year 2002) in order to illustrate and validate our method. All techniques are processed with the same computational framework, thus with the same models and a priori values for parameters. By using the same software and conventions, we avoid inconsistencies in individual computations. We process each technique individually and inside the combination. The comparison between these solutions is a way of analyzing the power of our method even if the actual status of our software does not reproduce the state-of-the-art analyses of each technique. However, we produce an analysis of the quality of our individual computations so that readers can get an informed appreciation of the current capabilities of our software. Finally, we present the capability of such combinations in terms of accuracy and precision, we underline the main issues of our method and propose solutions to solve them in the future. Numéro de notice : A2007-671 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2006JB004336 En ligne : https://doi.org/10.1029/2006JB004336 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102707
in Journal of geophysical research : Solid Earth > vol 112 n° B5 (May 2007)[article]Is there utility in rigorous combinations of VLBI and GPS Earth orientation parameters? / Jim Ray in Journal of geodesy, vol 79 n° 9 (December 2005)
[article]
Titre : Is there utility in rigorous combinations of VLBI and GPS Earth orientation parameters? Type de document : Article/Communication Auteurs : Jim Ray, Auteur ; Jan Kouba, Auteur ; Zuheir Altamimi , Auteur Année de publication : 2005 Article en page(s) : pp 505 - 511 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] données GPS
[Termes IGN] données ITGB
[Termes IGN] orientation de la Terre
[Termes IGN] point de liaison (géodésie)
[Termes IGN] positionnement par GPS
[Termes IGN] positionnement par ITGB
[Termes IGN] série temporelle
[Termes IGN] système de référence mondialRésumé : (Auteur) Combinations of station coordinates and velocities from independent space-geodetic techniques have long been the standard method to realize robust global terrestrial reference frames (TRFs). In principle, the particular strengths of one observing method can compensate for weaknesses in others if the combination is properly constructed, suitable weights are found, and accurate co-location ties are available. More recently, the methodology has been extended to combine time-series of results at the normal equation level. This allows Earth orientation parameters (EOPs) to be included and aligned in a fully consistent way with the TRF. While the utility of such multi-technique combinations is generally recognized for the reference frame, the benefits for the EOPs are yet to be quantitatively assessed. In this contribution, which is a sequel to a recent paper on co-location ties (Ray and Altamimi in J Geod 79(4–5): 189–195, 2005), we have studied test combinations of very long baseline interferometry (VLBI) and Global Positioning System (GPS) time-series solutions to evaluate the effects on combined EOP measurements compared with geophysical excitations. One expects any effect to be small, considering that GPS dominates the polar motion estimates due to its relatively dense and uniform global network coverage, high precision, continuous daily sampling, and homogeneity, while VLBI alone observes UT1-UTC. Presently, although clearly desirable, we see no practical method to rigorously include the GPS estimates of length-of-day variations due to significant time-varying biases. Nevertheless, our results, which are the first of this type, indicate that more accurate polar motion from GPS contributes to improved UT1-UTC results from VLBI. The situation with combined polar motion is more complex. The VLBI data contribute directly only very slightly, if at all, with an impact that is probably affected by the weakness of the current VLBI networks (small size and sparseness) and the quality of local ties relating the VLBI and GPS frames. Instead, the VLBI polar motion information is used primarily in rotationally aligning the VLBI and GPS frames, thereby reducing the dependence on co-location tie information. Further research is needed to determine an optimal VLBI-GPS combination strategy that yields the highest quality EOP estimates. Improved local ties (including internal systematic effects within the techniques) will be critically important in such an effort. Copyright Springer Numéro de notice : A2005-596 Affiliation des auteurs : IGN (1940-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-005-0007-7 Date de publication en ligne : 10/11/2005 En ligne : http://dx.doi.org/10.1007/s00190-005-0007-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27727
in Journal of geodesy > vol 79 n° 9 (December 2005) . - pp 505 - 511[article]Exemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 266-05091 RAB Revue Centre de documentation En réserve L003 Disponible 266-05092 RAB Revue Centre de documentation En réserve L003 Disponible Evaluation of co-location ties relating the VLBI and GPS reference frames / Jim Ray in Journal of geodesy, vol 79 n° 4-5 (July 2005)
[article]
Titre : Evaluation of co-location ties relating the VLBI and GPS reference frames Type de document : Article/Communication Auteurs : Jim Ray, Auteur ; Zuheir Altamimi , Auteur Année de publication : 2005 Article en page(s) : pp 189 - 195 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] interférométrie à très grande base
[Termes IGN] point de liaison (géodésie)
[Termes IGN] positionnement par GPS
[Termes IGN] positionnement par ITGB
[Termes IGN] série temporelle
[Termes IGN] système de référence mondialRésumé : (Auteur) We have compared the VLBI and GPS terrestrial reference frames, realized using 5 years of time-series observations of station positions and polar motion, with surveyed co-location tie vectors for 25 sites. The goal was to assess the overall quality of the ties and to determine whether a subset of co-location sites might be found with VLBI–GPS ties that are self-consistent within a few millimeters. Our procedure was designed to guard against internal distortion of the two space-geodetic networks and takes advantage of the reduction in tie information needed with the time-series combination method by using the very strong contribution due to co-location of the daily pole of rotation. The general quality of the available ties is somewhat discouraging in that most have residuals, compared to the space-geodetic frames, at the level of 1–2 cm. However, by a careful selection process, we have identified a subset of nine local VLBI–GPS ties that are consistent with each other and with space geodesy to better than 4 mm (RMS) in each component. While certainly promising, it is not possible to confidently assess the reliability of this particular subset without new information to verify the absolute accuracy of at least a few of the highest-quality ties. Particular care must be taken to demonstrate that possible systematic errors within the VLBI and GPS systems have been properly accounted for. A minimum of two (preferably three or four) ties must be measured with accuracies of 1 mm or better in each component, including any potential systematic effects. If this can be done, then the VLBI and GPS frames can be globally aligned to less than 1 mm in each Helmert component using our subset of nine ties. In any case, the X and Y rotations are better determined, to about 0.5 mm, due to the contribution of co-located polar motion. Copyright Springer Numéro de notice : A2005-593 Affiliation des auteurs : IGN (1940-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-005-0456-z Date de publication en ligne : 30/05/2005 En ligne : http://dx.doi.org/10.1007/s00190-005-0456-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27728
in Journal of geodesy > vol 79 n° 4-5 (July 2005) . - pp 189 - 195[article]Exemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 266-05062 RAB Revue Centre de documentation En réserve L003 Disponible 266-05061 RAB Revue Centre de documentation En réserve L003 Disponible Combination of space geodesy techniques for monitoring the kinematics of the Earth / David Coulot (2005)
Titre : Combination of space geodesy techniques for monitoring the kinematics of the Earth Type de document : Article/Communication Auteurs : David Coulot , Auteur ; Philippe Berio, Auteur ; Richard Biancale, Auteur ; et al., Auteur Editeur : Paris, Meudon et Nançay : Observatoire de Paris Année de publication : 2005 Conférence : JSRST 2004, Journées systèmes de référence spatio-temporels, 20/09/2004 22/09/2004 Paris France OA Proceedings Importance : pp 134 - 135 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] déformation de la croute terrestre
[Termes IGN] paramètres d'orientation de la Terre
[Termes IGN] positionnement par DORIS
[Termes IGN] positionnement par GPS
[Termes IGN] positionnement par ITGB
[Termes IGN] positionnement par télémétrie laser sur satellite
[Termes IGN] Terre (planète)Résumé : (auteur) In the framework of activities of the International Earth Rotation and Reference Systems Service (IERS) Combination Research Centres (CRC), the French Groupe de Recherche en Géodésie Spatiale (GRGS) studies the benefit of combining four geodetic techniques (SLR, VLBI, GPS and DORIS) at the measurement level in order to obtain a global and consistent solution for Earth Orientation Parameters (EOPs): polar motion xp and yp, universal time UT and celestial pole offsets in longitude and obliquity dψ and dǫ with a six-hour sampling, as well as weekly station positions. A one-year test period (the year 2002) has been chosen to prove the power of such a combination moreover worked out in a homogeneous global terrestrial reference frame. All techniques were processed in the same computational framework (GINS/DYNAMO) so with the same a priori models and a priori values for parameters. The optimal relative weights between each geodetic technique were obtained with an optimal variance component estimation method. Numéro de notice : C2004-042 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésNat DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103016 Voir aussiDocuments numériques
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