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A Terrestrial Reference Frame realised on the observation level using a GPS-LEO satellite constellation / Daniel Koenig in Journal of geodesy, vol 92 n° 11 (November 2018)
Titre : A Terrestrial Reference Frame realised on the observation level using a GPS-LEO satellite constellation Type de document : Article/Communication Auteurs : Daniel Koenig, Auteur Année de publication : 2018 Article en page(s) : pp 1299 - 1312 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes descripteurs IGN] champ de pesanteur terrestre
[Termes descripteurs IGN] données GPS
[Termes descripteurs IGN] données GRACE
[Termes descripteurs IGN] géocentre
[Termes descripteurs IGN] International Terrestrial Reference Frame
[Termes descripteurs IGN] transformation de HelmertRésumé : (Auteur) Applying a one-step integrated process, i.e. by simultaneously processing all data and determining all satellite orbits involved, a Terrestrial Reference Frame (TRF) consisting of a geometric as well as a dynamic part has been determined at the observation level using the EPOS-OC software of Deutsches GeoForschungsZentrum. The satellite systems involved comprise the Global Positioning System (GPS) as well as the twin GRACE spacecrafts. Applying a novel approach, the inherent datum defect has been overcome empirically. In order not to rely on theoretical assumptions this is done by carrying out the TRF estimation based on simulated observations and using the associated satellite orbits as background truth. The datum defect is identified here as the total of all three translations as well as the rotation about the z-axis of the ground station network leading to a rank-deficient estimation problem. To rectify this singularity, datum constraints comprising no-net translation (NNT) conditions in x, y, and z as well as a no-net rotation (NNR) condition about the z-axis are imposed. Thus minimally constrained, the TRF solution covers a time span of roughly a year with daily resolution. For the geometric part the focus is put on Helmert transformations between the a priori and the estimated sets of ground station positions, and the dynamic part is represented by gravity field coefficients of degree one and two. The results of a reference solution reveal the TRF parameters to be estimated reliably with high precision. Moreover, carrying out a comparable two-step approach using the same data and models leads to parameters and observational residuals of worse quality. A validation w.r.t. external sources shows the dynamic origin to coincide at a level of 5 mm or better in x and y, and mostly better than 15 mm in z. Comparing the derived GPS orbits to IGS final orbits as well as analysing the SLR residuals for the GRACE satellites reveals an orbit quality on the few cm level. Additional TRF test solutions demonstrate that K-Band Range-Rate observations between both GRACE spacecrafts are crucial for accurately estimating the dynamic frame’s orientation, and reveal the importance of the NNT- and NNR-conditions imposed for estimating the components of the dynamic geocenter. Numéro de notice : A2018-464 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1121-7 date de publication en ligne : 27/02/2018 En ligne : https://doi.org/10.1007/s00190-018-1121-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91063
in Journal of geodesy > vol 92 n° 11 (November 2018) . - pp 1299 - 1312[article]
Titre : Dependency of geodynamic parameters on the GNSS constellation Type de document : Article/Communication Auteurs : Stefano Scaramuzza, Auteur ; Rolf Dach, Auteur ; Gerhard Beutler, Auteur ; Daniel Arnold, Auteur ; Andreja Sušnik, Auteur ; Adrian Jäggi, Auteur Année de publication : 2018 Article en page(s) : pp 93 - 104 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes descripteurs IGN] constellation GLONASS
[Termes descripteurs IGN] constellation GPS
[Termes descripteurs IGN] géocentre
[Termes descripteurs IGN] mouvement du pôle
[Termes descripteurs IGN] orbite
[Termes descripteurs IGN] série temporelleRésumé : (Auteur) Significant differences in time series of geodynamic parameters determined with different Global Navigation Satellite Systems (GNSS) exist and are only partially explained. We study whether the different number of orbital planes within a particular GNSS contributes to the observed differences by analyzing time series of geocenter coordinates (GCCs) and pole coordinates estimated from several real and virtual GNSS constellations: GPS, GLONASS, a combined GPS/GLONASS constellation, and two virtual GPS sub-systems, which are obtained by splitting up the original GPS constellation into two groups of three orbital planes each. The computed constellation-specific GCCs and pole coordinates are analyzed for systematic differences, and their spectral behavior and formal errors are inspected. We show that the number of orbital planes barely influences the geocenter estimates. GLONASS’ larger inclination and formal errors of the orbits seem to be the main reason for the initially observed differences. A smaller number of orbital planes may lead, however, to degradations in the estimates of the pole coordinates. A clear signal at three cycles per year is visible in the spectra of the differences between our estimates of the pole coordinates and the corresponding IERS 08 C04 values. Combinations of two 3-plane systems, even with similar ascending nodes, reduce this signal. The understanding of the relation between the satellite constellations and the resulting geodynamic parameters is important, because the GNSS currently under development, such as the European Galileo and the medium Earth orbit constellation of the Chinese BeiDou system, also consist of only three orbital planes. Numéro de notice : A2018-012 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1047-5 En ligne : https://doi.org/10.1007/s00190-017-1047-5 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89055
in Journal of geodesy > vol 92 n° 1 (January 2018) . - pp 93 - 104[article]
Titre : Seasonal low-degree changes in terrestrial water mass load from global GNSS measurements Type de document : Article/Communication Auteurs : Thierry Meyrath, Auteur ; Tonie M. van Dam, Auteur ; Xavier Collilieux Année de publication : 2017 Projets : 1-Pas de projet / Article en page(s) : pp 1 - 22 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes descripteurs IGN] coordonnées GNSS
[Termes descripteurs IGN] géocentre
[Termes descripteurs IGN] masse d'eau
[Termes descripteurs IGN] mouvement du géocentre
[Termes descripteurs IGN] surcharge océanique
[Termes descripteurs IGN] variation saisonnièreRésumé : (auteur) Large-scale mass redistribution in the terrestrial water storage (TWS) leads to changes in the low-degree spherical harmonic coefficients of the Earth’s surface mass density field. Studying these low-degree fluctuations is an important task that contributes to our understanding of continental hydrology. In this study, we use global GNSS measurements of vertical and horizontal crustal displacements that we correct for atmospheric and oceanic effects, and use a set of modified basis functions similar to Clarke et al. (Geophys J Int 171:1–10, 2007) to perform an inversion of the corrected measurements in order to recover changes in the coefficients of degree-0 (hydrological mass change), degree-1 (centre of mass shift) and degree-2 (flattening of the Earth) caused by variations in the TWS over the period January 2003–January 2015. We infer from the GNSS-derived degree-0 estimate an annual variation in total continental water mass with an amplitude of (3.49±0.19)×103 Gt and a phase of 70∘±3∘ (implying a peak in early March), in excellent agreement with corresponding values derived from the Global Land Data Assimilation System (GLDAS) water storage model that amount to (3.39±0.10)×103 Gt and 71∘±2∘, respectively. The degree-1 coefficients we recover from GNSS predict annual geocentre motion (i.e. the offset change between the centre of common mass and the centre of figure) caused by changes in TWS with amplitudes of 0.69±0.07 mm for GX, 1.31±0.08 mm for GY and 2.60±0.13 mm for GZ. These values agree with GLDAS and estimates obtained from the combination of GRACE and the output of an ocean model using the approach of Swenson et al. (J Geophys Res 113(B8), 2008) at the level of about 0.5, 0.3 and 0.9 mm for GX, GY and GZ, respectively. Corresponding degree-1 coefficients from SLR, however, generally show higher variability and predict larger amplitudes for GX and GZ. The results we obtain for the degree-2 coefficients from GNSS are slightly mixed, and the level of agreement with the other sources heavily depends on the individual coefficient being investigated. The best agreement is observed for TC20 and TS22, which contain the most prominent annual signals among the degree-2 coefficients, with amplitudes amounting to (5.47±0.44)×10−3 and (4.52±0.31)×10−3 m of equivalent water height (EWH), respectively, as inferred from GNSS. Corresponding agreement with values from SLR and GRACE is at the level of or better than 0.4×10−3 and 0.9×10−3 m of EWH for TC20 and TS22, respectively, while for both coefficients, GLDAS predicts smaller amplitudes. Somewhat lower agreement is obtained for the order-1 coefficients, TC21 and TS21, while our GNSS inversion seems unable to reliably recover TC22. For all the coefficients we consider, the GNSS-derived estimates from the modified inversion approach are more consistent with the solutions from the other sources than corresponding estimates obtained from an unconstrained standard inversion. Numéro de notice : A2017-311 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1028-8 date de publication en ligne : 25/04/2017 En ligne : http://doi.org/10.1007/s00190-017-1028-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85361
in Journal of geodesy > vol 91 n° 11 (November 2017) . - pp 1 - 22[article]
Titre : Assessment of the accuracy of global geodetic satellite laser ranging observations and estimated impact on ITRF scale: estimation of systematic errors in LAGEOS observations 1993–2014 Type de document : Article/Communication Auteurs : Graham Appleby, Auteur ; José Rodríguez, Auteur ; Zuheir Altamimi Année de publication : 2016 Article en page(s) : pp 1371 - 1388 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes descripteurs IGN] analyse diachronique
[Termes descripteurs IGN] champ de gravitation
[Termes descripteurs IGN] constante
[Termes descripteurs IGN] données Lageos
[Termes descripteurs IGN] données TLS (télémétrie)
[Termes descripteurs IGN] erreur systématique
[Termes descripteurs IGN] géocentre
[Termes descripteurs IGN] système de référence géodésiqueRésumé : (Auteur) Satellite laser ranging (SLR) to the geodetic satellites LAGEOS and LAGEOS-2 uniquely determines the origin of the terrestrial reference frame and, jointly with very long baseline interferometry, its scale. Given such a fundamental role in satellite geodesy, it is crucial that any systematic errors in either technique are at an absolute minimum as efforts continue to realise the reference frame at millimetre levels of accuracy to meet the present and future science requirements. Here, we examine the intrinsic accuracy of SLR measurements made by tracking stations of the International Laser Ranging Service using normal point observations of the two LAGEOS satellites in the period 1993 to 2014. The approach we investigate in this paper is to compute weekly reference frame solutions solving for satellite initial state vectors, station coordinates and daily Earth orientation parameters, estimating along with these weekly average range errors for each and every one of the observing stations. Potential issues in any of the large number of SLR stations assumed to have been free of error in previous realisations of the ITRF may have been absorbed in the reference frame, primarily in station height. Likewise, systematic range errors estimated against a fixed frame that may itself suffer from accuracy issues will absorb network-wide problems into station-specific results. Our results suggest that in the past two decades, the scale of the ITRF derived from the SLR technique has been close to 0.7 ppb too small, due to systematic errors either or both in the range measurements and their treatment. We discuss these results in the context of preparations for ITRF2014 and additionally consider the impact of this work on the currently adopted value of the geocentric gravitational constant, GM. Numéro de notice : A2016-808 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0929-2 date de publication en ligne : 29/06/2016 En ligne : http://dx.doi.org/10.1007/s00190-016-0929-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82596
in Journal of geodesy > vol 90 n° 12 (December 2016) . - pp 1371 - 1388[article]
Titre : The IGS contribution to ITRF2014 Type de document : Article/Communication Auteurs : Paul Rebischung 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 descripteurs IGN] données GNSS
[Termes descripteurs IGN] estimation de précision
[Termes descripteurs IGN] géocentre
[Termes descripteurs IGN] International Terrestrial Reference Frame
[Termes descripteurs IGN] réseau géodésique terrestreRésumé : (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 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
in Journal of geodesy > vol 90 n° 7 (July 2016) . - pp 611 – 630[article]PermalinkPermalinkPermalinkCombination of GNSS and SLR measurements : contribution to the realization of the terrestrial reference frame / Sara Bruni (2016)
PermalinkPermalinkPermalinkPermalinkDetermination of precise satellite orbits and geodetic parameters using satellite laser ranging / Krzysztof Sosnica (2015)
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