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ITRF2008: an improved solution of the international terrestrial reference frame / Zuheir Altamimi in Journal of geodesy, vol 85 n° 8 (August 2011)    

Public [article]  inJournal of geodesy > vol 85 n° 8 (August 2011) . - pp 457 - 473 Titre : ITRF2008: an improved solution of the international terrestrial reference frame Type de document : Article/Communication Auteurs : Zuheir Altamimi , Auteur ; Xavier Collilieux , Auteur ; Laurent Métivier , Auteur Année de publication : 2011 Projets : 1-Pas de projet / Article en page(s) : pp 457 - 473 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] exactitude des données [Termes IGN] International Terrestrial Reference Frame [Termes IGN] rotation de la Terre [Termes IGN] série temporelle [Termes IGN] système de référence mondial [Termes IGN] télémétrie laser sur satellite Résumé : (Auteur) ITRF2008 is a refined version of the International Terrestrial Reference Frame based on reprocessed solutions of the four space geodetic techniques: VLBI, SLR, GPS and DORIS, spanning 29, 26, 12.5 and 16 years of observations, respectively. The input data used in its elaboration are time series (weekly from satellite techniques and 24-h session-wise from VLBI) of station positions and daily Earth Orientation Parameters (EOPs). The ITRF2008 origin is defined in such a way that it has zero translations and translation rates with respect to the mean Earth center of mass, averaged by the SLR time series. Its scale is defined by nullifying the scale factor and its rate with respect to the mean of VLBI and SLR long-term solutions as obtained by stacking their respective time series. The scale agreement between these two technique solutions is estimated to be 1.05 + 0.13 ppb at epoch 2005.0 and 0.049 + 0.010 ppb/yr. The ITRF2008 orientation (at epoch 2005.0) and its rate are aligned to the ITRF2005 using 179 stations of high geodetic quality. An estimate of the origin components from ITRF2008 to ITRF2005 (both origins are defined by SLR) indicates differences at epoch 2005.0, namely: -0.5, -0.9 and -4.7 mm along X, Y and Z-axis, respectively. The translation rate differences between the two frames are zero for Y and Z, while we observe an X-translation rate of 0.3 mm/yr. The estimated formal errors of these parameters are 0.2 mm and 0.2 mm/yr, respectively. The high level of origin agreement between ITRF2008 and ITRF2005 is an indication of an imprecise ITRF2000 origin that exhibits a Z-translation drift of 1.8 mm/yr with respect to ITRF2005. An evaluation of the ITRF2008 origin accuracy based on the level of its agreement with ITRF2005 is believed to be at the level of 1 cm over the time-span of the SLR observations. Considering the level of scale consistency between VLBI and SLR, the ITRF2008 scale accuracy is evaluated to be at the level of 1.2 ppb (8 mm at the equator) over the common time-span of the observations of both techniques. Although the performance of the ITRF2008 is demonstrated to be higher than ITRF2005, future ITRF improvement resides in improving the consistency between local ties in co-location sites and space geodesy estimates. Numéro de notice : A2011-356 Affiliation des auteurs : LAREG (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0444-4 Date de publication en ligne : 03/02/2011 En ligne : https://doi.org/10.1007/s00190-011-0444-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31135 [article]

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Documents numériques

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Transverse Mercator with an accuracy of a few nanometers / C. Karney in Journal of geodesy, vol 85 n° 8 (August 2011)  

Public [article]  inJournal of geodesy > vol 85 n° 8 (August 2011) . - pp 475 - 485 Titre : Transverse Mercator with an accuracy of a few nanometers Type de document : Article/Communication Auteurs : C. Karney, Auteur Année de publication : 2011 Article en page(s) : pp 475 - 485 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Projections [Termes IGN] convergence des méridiens [Termes IGN] ellipsoïde (géodésie) [Termes IGN] précision submillimétrique [Termes IGN] projection [Termes IGN] projection conforme [Termes IGN] projection de Gauss [Termes IGN] projection Universal Transverse Mercator Résumé : (Auteur) Implementations of two algorithms for the transverse Mercator projection are described; these achieve accuracies close to machine precision. One is based on the exact equations of Thompson and Lee and the other uses an extension of Krüger’s series for the mapping to higher order. The exact method provides an accuracy of 9 nm over the entire ellipsoid, while the errors in the series method are less than 5 nm within 3900 km of the central meridian. In each case, the meridian convergence and scale are also computed with similar accuracy. The speed of the series method is competitive with other less accurate algorithms and the exact method is about five times slower. Numéro de notice : A2011-357 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0445-3 Date de publication en ligne : 09/02/2011 En ligne : https://doi.org/10.1007/s00190-011-0445-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31136 [article]

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An evaluation of solar radiation pressure strategies for the GPS constellation / Ant Sibthorpe in Journal of geodesy, vol 85 n° 8 (August 2011)  

Public [article]  inJournal of geodesy > vol 85 n° 8 (August 2011) . - pp 505 - 517 Titre : An evaluation of solar radiation pressure strategies for the GPS constellation Type de document : Article/Communication Auteurs : Ant Sibthorpe, Auteur ; Willy I. Bertiger, Auteur ; Shailen Desai, Auteur ; et al., Auteur Année de publication : 2011 Article en page(s) : pp 505 - 517 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] analyse comparative [Termes IGN] constellation GPS [Termes IGN] données TLS (télémétrie) [Termes IGN] GIPSY-OASIS [Termes IGN] international GPS service for geodynamics [Termes IGN] orbitographie [Termes IGN] rayonnement solaire [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) The subtle effects of different Global Positioning System (GPS) satellite force models are becoming apparent now that mature processing strategies are reaching new levels of accuracy and precision. For this paper, we tested several approaches to solar radiation pressure (SRP) modeling that are commonly used by International GNSS Service (IGS) analysis centers. These include the GPS Solar Pressure Model (GSPM; Bar-Sever and Kuang in The Interplanetary Network Progress Report 42-160, 2005) and variants of the so-called DYB model (Springer et al. in Adv Space Res 23:673–676, 1999). Our results show that currently observed differences between GPS orbit solutions from the various IGS analysis centers are in large part explained by differences between their respective approaches to modeling SRP. DYB-based strategies typically generate orbit solutions that have the smallest differences with respect to the IGS final combined solution, largely because the DYB approach is most commonly used by the contributing analysis centers. However, various internal and external metrics, including ambiguity resolution statistics and satellite laser ranging observations, support continued use of the GSPM-based approach for precise orbit determination of the GPS constellation, at least when using the GIPSY-OASIS software. Numéro de notice : A2011-358 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0450-6 Date de publication en ligne : 19/02/2011 En ligne : https://doi.org/10.1007/s00190-011-0450-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31137 [article]

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4D GPS water vapor tomography: new parameterized approaches / Donat Perler in Journal of geodesy, vol 85 n° 8 (August 2011)  

Public [article]  inJournal of geodesy > vol 85 n° 8 (August 2011) . - pp 539 - 550 Titre : 4D GPS water vapor tomography: new parameterized approaches Type de document : Article/Communication Auteurs : Donat Perler, Auteur ; Alain Geiger, Auteur ; Fabian Peter Hurter, Auteur Année de publication : 2011 Article en page(s) : pp 539 - 550 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Alpes [Termes IGN] coordonnées ellipsoïdales [Termes IGN] distribution spatiale [Termes IGN] données GPS [Termes IGN] données météorologiques [Termes IGN] filtre de Kalman [Termes IGN] prédiction [Termes IGN] réfraction atmosphérique [Termes IGN] réfringence [Termes IGN] signal GPS [Termes IGN] Suisse [Termes IGN] tomographie [Termes IGN] troposphère [Termes IGN] vapeur d'eau [Termes IGN] voxel Résumé : (Auteur) Water vapor is a key variable in numerical weather prediction, as it plays an important role in atmospheric processes. Nonetheless, the distribution of water vapor in the atmosphere is observed with a coarse resolution in time and space compared to the resolution of numerical weather models. GPS water vapor tomography is one of the promising methods to improve the resolution of water vapor measurements. This paper presents new parameterized approaches for the determination of water vapor distribution in the troposphere by GPS. We present the methods and give first results validating the approaches. The parameterization of voxels (volumetric pixels) by trilinear and spline functions in ellipsoidal coordinates are introduced in this study. The evolution in time of the refractivity field is modeled by a Kalman filter with a temporal resolution of 30s, which corresponds to the available GPS-data rate. The algorithms are tested with simulated and with real data from more than 40 permanent GPS receiver stations in Switzerland and adjoining regions covering alpine areas. The investigations show the potential of the new parameterized approaches to yield superior results compared to the non parametric classical one. The accuracy of the tomographic result is quantified by the inter-quartile range (IQR), which is decreased by 10–20% with the new approaches. Further, parameterized voxel solutions have a substantially smaller maximal error than the non parameterized ones. Simulations show a limited ability to resolve vertical structures above the top station of the network with GPS tomography. Numéro de notice : A2011-359 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0454-2 Date de publication en ligne : 08/03/2011 En ligne : https://doi.org/10.1007/s00190-011-0454-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31138 [article]

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