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Precise station positions from VLBI observations to satellites: a simulation study / Lucia Plank in Journal of geodesy, vol 88 n° 7 (July 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 7 (July 2014) . - pp 659 - 673 Titre : Precise station positions from VLBI observations to satellites: a simulation study Type de document : Article/Communication Auteurs : Lucia Plank, Auteur ; Johannes Böhm , Auteur ; Harald Schuh, Auteur Année de publication : 2014 Article en page(s) : pp 659 - 673 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] International Terrestrial Reference Frame [Termes IGN] orbite [Termes IGN] positionnement par ITGB [Termes IGN] poursuite de satellite [Termes IGN] station GPS [Termes IGN] système de référence mondial Résumé : (Auteur) Very long baseline interferometry (VLBI) tracking of satellites is a topic of increasing interest for the establishment of space ties. This shall strengthen the connection of the various space geodetic techniques that contribute to the International Terrestrial Reference Frame. The concept of observing near-Earth satellites demands research on possible observing strategies. In this paper, we introduce this concept and discuss its possible benefits for improving future realizations of the International Terrestrial Reference System. Using simulated observations, we develop possible observing strategies that allow the determination of radio telescope positions in the satellite system on Earth with accuracies of a few millimeters up to 1–2 cm for weekly station coordinates. This is shown for satellites with orbital heights between 2,000 and 6,000 km, observed by dense regional as well as by global VLBI-networks. The number of observations, as mainly determined by the satellite orbit and the observation interval, is identified as the most critical parameter that affects the expected accuracies. For observations of global positioning system satellites, we propose the combination with classical VLBI to radio sources or a multi-satellite strategy. Both approaches allow station position repeatabilities of a few millimeters for weekly solutions. Numéro de notice : A2014-413 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0712-1 Date de publication en ligne : 23/03/2014 En ligne : https://doi.org/10.1007/s00190-014-0712-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=73950 [article]

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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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Voxel-optimized regional water vapor tomography and comparison with radiosonde and numerical weather model / Biyan Chen in Journal of geodesy, vol 88 n° 7 (July 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 7 (July 2014) . - pp 691 - 703 Titre : Voxel-optimized regional water vapor tomography and comparison with radiosonde and numerical weather model Type de document : Article/Communication Auteurs : Biyan Chen, Auteur ; Z. Liu, Auteur Année de publication : 2014 Article en page(s) : pp 691 - 703 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] positionnement par GNSS [Termes IGN] tomographie [Termes IGN] vapeur d'eau [Termes IGN] voxel Résumé : (Auteur)Water vapor tomography has been developed as a powerful tool to model spatial and temporal distribution of atmospheric water vapor. Global navigation satellite systems (GNSS) water vapor tomography refers to the 3D structural construction of tropospheric water vapor using a large number of GNSS signals that penetrate the tomographic modeling area from different positions. The modeling area is usually discretized into a number of voxels. A major issue involved is that some voxels are not crossed by any GNSS signal rays, resulting in an undetermined solution to the tomographic system. To alleviate this problem, the number of voxels crossed by GNSS signal rays should be as large as possible. An important way to achieve this is to optimize the geographic distribution of tomographic voxels. We propose an approach to optimize voxel distribution in both vertical and horizontal domains. In the vertical domain, water vapor profiles derived from radiosonde data are exploited to identify the maximum height of tomography and the optimal vertical resolution. In the horizontal domain, the optimal horizontal distribution of voxels is obtained by searching the maximum number of ray-crossing voxels in both latitude and longitude directions. The water vapor tomography optimization procedures are implemented using GPS water vapor data from the Hong Kong Satellite Positioning Reference Station Network. The tomographic water vapor fields solved from the optimized tomographic voxels are evaluated using radiosonde data and a numerical weather prediction non-hydrostatic model (NHM) obtained for the Hong Kong station. The comparisons of tomographic integrated water vapor (IWV) with the radiosonde and NHM IWV show that RMS errors of their differences are 1.41 and 3.09 mm, respectively. Moreover, the tomographic water vapor density results are compared with those of radiosonde and NHM. The RMS error of the density differences between tomography and radiosonde data is 1.05 g/m3 . For the comparison between tomography and NHM, an overall RMS error of 1.43g/m3 is achieved. Numéro de notice : A2014-415 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 : 08/04/2014 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=73956 [article]

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