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Termes descripteurs IGN > sciences naturelles > sciences de la Terre et de l'univers > géosciences > géophysique interne > géodésie > point de liaison (géodésie)
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Modeling the VLBI delay for Earth satellites / Frédéric Jaron in Journal of geodesy, vol 93 n°7 (July 2019)
Titre : Modeling the VLBI delay for Earth satellites Type de document : Article/Communication Auteurs : Frédéric Jaron, Auteur ; Axel Nothnagel, Auteur Année de publication : 2019 Article en page(s) : pp 953 - 961 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes descripteurs IGN] E-GRASP
[Termes descripteurs IGN] Geodetic Reference Antenna in Space
[Termes descripteurs IGN] interférométrie à très grande base
[Termes descripteurs IGN] point de liaison (géodésie)
[Termes descripteurs IGN] poursuite de satellite
[Termes descripteurs IGN] propagation du signal
[Termes descripteurs IGN] retard troposphérique
[Termes descripteurs IGN] système international de référence célesteRésumé : (auteur) Very-long-baseline interferometry (VLBI) observations of satellites orbiting the Earth and emitting an artificial radio signal have the potential of becoming an important technique for improving the frame ties between celestial and terrestrial reference frames. Modeling the delay of the signal reception at one station with respect to the other station of a baseline is a fundamental step for correlation and parameter estimation. The near-field VLBI delay models developed so far include numerical computation, which may become expensive in terms of computation time. This applies especially when partial derivatives are to be computed, which is the normal case for least squares adjustments. Furthermore, all the models are formulated in the barycentric celestial reference system requiring large numbers. Here we present an analytical expression for the VLBI delay for the special case of satellites orbiting the Earth, observed by ground-based radio telescopes. We analytically solve the light time equation for each signal propagation path from the source to receiver one and to receiver two under the simplification of linearizing the trajectory of the satellite. By approximating the motion of the Earth as uniform during the short signal travel times we are able to work in the geocentric celestial reference system. We investigate differences between numerical and analytical solutions by simulating VLBI observations of Earth satellites. These tests reveal that delays computed with the analytical formula are consistent with those computed with the numerical solution below the detection level of VLBI but at less computational cost. Numéro de notice : A2019-354 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1217-0 date de publication en ligne : 20/11/2018 En ligne : https://doi.org/10.1007/s00190-018-1217-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93408
in Journal of geodesy > vol 93 n°7 (July 2019) . - pp 953 - 961[article]
Titre : Assessment of local GNSS baselines at co-location sites Type de document : Article/Communication Auteurs : Iván Herrera Pinzón, Auteur ; Markus Rothacher, Auteur Année de publication : 2018 Article en page(s) : pp 1079 - 1095 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes descripteurs IGN] co-positionnement
[Termes descripteurs IGN] erreur systématique
[Termes descripteurs IGN] International Terrestrial Reference Frame
[Termes descripteurs IGN] ligne de base
[Termes descripteurs IGN] point de liaison (géodésie)
[Termes descripteurs IGN] positionnement par GNSS
[Termes descripteurs IGN] retard troposphérique zénithal
[Termes descripteurs IGN] série temporelle
[Termes descripteurs IGN] station permanenteRésumé : (Auteur) As one of the major contributors to the realisation of the International Terrestrial Reference System (ITRS), the Global Navigation Satellite Systems (GNSS) are prone to suffer from irregularities and discontinuities in time series. While often associated with hardware/software changes and the influence of the local environment, these discrepancies constitute a major threat for ITRS realisations. Co-located GNSS at fundamental sites, with two or more available instruments, provide the opportunity to mitigate their influence while improving the accuracy of estimated positions by examining data breaks, local biases, deformations, time-dependent variations and the comparison of GNSS baselines with existing local tie measurements. With the use of co-located GNSS data from a subset sites of the International GNSS Service network, this paper discusses a global multi-year analysis with the aim of delivering homogeneous time series of coordinates to analyse system-specific error sources in the local baselines. Results based on the comparison of different GNSS-based solutions with the local survey ties show discrepancies of up to 10 mm despite GNSS coordinate repeatabilities at the sub-mm level. The discrepancies are especially large for the solutions using the ionosphere-free linear combination and estimating tropospheric zenith delays, thus corresponding to the processing strategy used for global solutions. Snow on the antennas causes further problems and seasonal variations of the station coordinates. These demonstrate the need for a permanent high-quality monitoring of the effects present in the short GNSS baselines at fundamental sites. Numéro de notice : A2018-459 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1108-9 date de publication en ligne : 17/01/2018 En ligne : https://doi.org/10.1007/s00190-017-1108-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91056
in Journal of geodesy > vol 92 n° 9 (September 2018) . - pp 1079 - 1095[article]
Titre : Consistent realization of celestial and terrestrial reference frames Type de document : Article/Communication Auteurs : Younghee Kwak, Auteur ; Mathis Blossfeld, Auteur ; Ralf Schmid, Auteur ; Detlef Angermann, Auteur ; Michael Gerstl, Auteur ; Manuela Seitz, Auteur Année de publication : 2018 Article en page(s) : pp 1047 - 1061 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes descripteurs IGN] cohérence des données
[Termes descripteurs IGN] erreur systématique inter-systèmes
[Termes descripteurs IGN] International Terrestrial Reference Frame
[Termes descripteurs IGN] paramètres d'orientation de la Terre
[Termes descripteurs IGN] point de liaison (géodésie)
[Termes descripteurs IGN] système de référence célesteRésumé : (Auteur) The Celestial Reference System (CRS) is currently realized only by Very Long Baseline Interferometry (VLBI) because it is the space geodetic technique that enables observations in that frame. In contrast, the Terrestrial Reference System (TRS) is realized by means of the combination of four space geodetic techniques: Global Navigation Satellite System (GNSS), VLBI, Satellite Laser Ranging (SLR), and Doppler Orbitography and Radiopositioning Integrated by Satellite. The Earth orientation parameters (EOP) are the link between the two types of systems, CRS and TRS. The EOP series of the International Earth Rotation and Reference Systems Service were combined of specifically selected series from various analysis centers. Other EOP series were generated by a simultaneous estimation together with the TRF while the CRF was fixed. Those computation approaches entail inherent inconsistencies between TRF, EOP, and CRF, also because the input data sets are different. A combined normal equation (NEQ) system, which consists of all the parameters, i.e., TRF, EOP, and CRF, would overcome such an inconsistency. In this paper, we simultaneously estimate TRF, EOP, and CRF from an inter-technique combined NEQ using the latest GNSS, VLBI, and SLR data (2005–2015). The results show that the selection of local ties is most critical to the TRF. The combination of pole coordinates is beneficial for the CRF, whereas the combination of ΔUT1 results in clear rotations of the estimated CRF. However, the standard deviations of the EOP and the CRF improve by the inter-technique combination which indicates the benefits of a common estimation of all parameters. It became evident that the common determination of TRF, EOP, and CRF systematically influences future ICRF computations at the level of several μas. Moreover, the CRF is influenced by up to 50 μas if the station coordinates and EOP are dominated by the satellite techniques. Numéro de notice : A2018-458 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1130-6 date de publication en ligne : 12/03/2018 En ligne : https://doi.org/10.1007/s00190-018-1130-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91055
in Journal of geodesy > vol 92 n° 9 (September 2018) . - pp 1047 - 1061[article]
Titre : Assessment of the possible contribution of space ties on-board GNSS satellites to the terrestrial reference frame Type de document : Article/Communication Auteurs : Sara Bruni, Auteur ; Paul Rebischung Année de publication : 2018 Article en page(s) : pp 383 - 399 Note générale : bibliographie
This work was performed under grant ECOCZE RB from the Università di Bologna.Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes descripteurs IGN] International Terrestrial Reference Frame
[Termes descripteurs IGN] point de liaison (géodésie)
[Termes descripteurs IGN] positionnement par GNSS
[Termes descripteurs IGN] positionnement par télémétrie laser sur satelliteRésumé : (auteur) The realization of the international terrestrial reference frame (ITRF) is currently based on the data provided by four space geodetic techniques. The accuracy of the different technique-dependent materializations of the frame physical parameters (origin and scale) varies according to the nature of the relevant observables and to the impact of technique-specific errors. A reliable computation of the ITRF requires combining the different inputs, so that the strengths of each technique can compensate for the weaknesses of the others. This combination, however, can only be performed providing some additional information which allows tying together the independent technique networks. At present, the links used for that purpose are topometric surveys (local/terrestrial ties) available at ITRF sites hosting instruments of different techniques. In principle, a possible alternative could be offered by spacecrafts accommodating the positioning payloads of multiple geodetic techniques realizing their co-location in orbit (space ties). In this paper, the GNSS–SLR space ties on-board GPS and GLONASS satellites are thoroughly examined in the framework of global reference frame computations. The investigation focuses on the quality of the realized physical frame parameters. According to the achieved results, the space ties on-board GNSS satellites cannot, at present, substitute terrestrial ties in the computation of the ITRF. The study is completed by a series of synthetic simulations investigating the impact that substantial improvements in the volume and quality of SLR observations to GNSS satellites would have on the precision of the GNSS frame parameters. Numéro de notice : A2018-050 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1069-z date de publication en ligne : 06/10/2017 En ligne : https://doi.org/10.1007/s00190-017-1069-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89354
in Journal of geodesy > vol 92 n° 4 (April 2018) . - pp 383 - 399[article]
Titre : A global terrestrial reference frame from simulated VLBI and SLR data in view of GGOS Type de document : Article/Communication Auteurs : Susanne Glaser, Auteur ; Rolf König, Auteur ; Dimitrios Ampatzidis, Auteur ; Tobias Nilsson, Auteur ; Robert Heinkelmann, Auteur ; Frank Flechtner, Auteur ; Harald Schuh, Auteur Année de publication : 2017 Article en page(s) : pp 723 - 733 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes descripteurs IGN] données ITGB
[Termes descripteurs IGN] données TLS (télémétrie)
[Termes descripteurs IGN] Global Geodetic Observing System
[Termes descripteurs IGN] paramètres d'orientation de la Terre
[Termes descripteurs IGN] point de liaison (géodésie)
[Termes descripteurs IGN] repère de référence
[Termes descripteurs IGN] simulationRésumé : (Auteur) In this study, we assess the impact of two combination strategies, namely local ties (LT) and global ties (GT), on the datum realization of Global Terrestrial Reference Frames in view of the Global Geodetic Observing System requiring 1 mm-accuracy. Simulated Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data over a 7 year time span was used. The LT results show that the geodetic datum can be best transferred if the precision of the LT is at least 1 mm. Investigating different numbers of LT, the lack of co-located sites on the southern hemisphere is evidenced by differences of 9 mm in translation and rotation compared to the solution using all available LT. For the GT, the combination applying all Earth rotation parameters (ERP), such as pole coordinates and UT1-UTC, indicates that the rotation around the Z axis cannot be adequately transferred from VLBI to SLR within the combination. Applying exclusively the pole coordinates as GT, we show that the datum can be transferred with mm-accuracy within the combination. Furthermore, adding artificial stations in Tahiti and Nigeria to the current VLBI network results in an improvement in station positions by 13 and 12%, respectively, and in ERP by 17 and 11%, respectively. Extending to every day VLBI observations leads to 65% better ERP estimates compared to usual twice-weekly VLBI observations. Numéro de notice : A2017-295 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern En ligne : http://doi.org/10.1007/s00190-017-1021-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85330
in Journal of geodesy > vol 91 n° 7 (July 2017) . - pp 723 - 733[article]PermalinkPermalinkPermalinkIGN best practice for surveying instrument reference points at ITRF co-location sites / Jean-Claude Poyard (2017)
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