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Auteur David Lavallée |
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Affiner la recherche Interroger des sources externesSecular changes in Earth’s shape and surface mass loading derived from combinations of reprocessed global GPS networks / david Booker in Journal of geodesy, vol 88 n° 9 (September 2014)
Titre : Secular changes in Earth’s shape and surface mass loading derived from combinations of reprocessed global GPS networks Type de document : Article/Communication Auteurs : david Booker, Auteur ; Peter J. Clarke, Auteur ; David Lavallée, Auteur Année de publication : 2014 Article en page(s) : pp 839 - 855 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] croute terrestre
[Termes IGN] détection de changement
[Termes IGN] masse d'eau
[Termes IGN] masse de la Terre
[Termes IGN] traitement de données GNSSRésumé : (Auteur) The changing distribution of surface mass (oceans, atmospheric pressure, continental water storage, groundwater, lakes, snow and ice) causes detectable changes in the shape of the solid Earth, on time scales ranging from hours to millennia. Transient changes in the Earth’s shape can, regardless of cause, be readily separated from steady secular variation in surface mass loading, but other secular changes due to plate tectonics and glacial isostatic adjustment (GIA) cannot. We estimate secular station velocities from almost 11 years of high quality combined GPS position solutions (GPS weeks 1,000–1,570) submitted as part of the first international global navigation satellite system service reprocessing campaign. Individual station velocities are estimated as a linear fit, paying careful attention to outliers and offsets. We remove a suite of a priori GIA models, each with an associated set of plate tectonic Euler vectors estimated by us; the latter are shown to be insensitive to the a priori GIA model. From the coordinate time series residuals after removing the GIA models and corresponding plate tectonic velocities, we use mass-conserving continental basis functions to estimate surface mass loading including the secular term. The different GIA models lead to significant differences in the estimates of loading in selected regions. Although our loading estimates are broadly comparable with independent estimates from other satellite missions, their range highlights the need for better, more robust GIA models that incorporate 3D Earth structure and accurately represent 3D surface displacements. Numéro de notice : A2014-455 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0725-9 Date de publication en ligne : 06/05/2014 En ligne : https://doi.org/10.1007/s00190-014-0725-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74027
in Journal of geodesy > vol 88 n° 9 (September 2014) . - pp 839 - 855[article]Réservation
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Titre : A dense global velocity field based on GNSS observations: Preliminary Results Type de document : Article/Communication Auteurs : Carine Bruyninx, Auteur ; Zuheir Altamimi Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2012 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 136 Conférence : IAG 2009 Symposium, Geodesy for Planet Earth 31/08/2009 04/09/2009 Buenos Aires Argentine Proceedings Springer Importance : pp 19 - 26 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de vitesse
[Termes IGN] coordonnées cartésiennes géocentriques
[Termes IGN] déformation verticale de la croute terrestre
[Termes IGN] réseau permanent EUREF
[Termes IGN] série temporelleRésumé : (auteur) In a collaborative effort with the regional sub-commissions within IAG sub-commission 1.3 “Regional Reference Frames”, the IAG Working Group (WG) on “Regional Dense Velocity Fields” (see http://epncb.oma.be/IAG) has made a first attempt to create a dense global velocity field. GNSS-based velocity solutions for more than 6,000 continuous and episodic GNSS tracking stations, were proposed to the WG in reply to the first call for participation issued in November 2008. The combination of a part of these solutions was done in a two-step approach: first at the regional level, and secondly at the global level. Comparisons between different velocity solutions show an RMS agreement between 0.3 and 0.5 mm/year resp. for the horizontal and vertical velocities. In some cases, significant disagreements between the velocities of some of the networks are seen, but these are primarily caused by the inconsistent handling of discontinuity epochs and solution numbers. In the future, the WG will re-visit the procedures in order to develop a combination process that is efficient, automated, transparent, and not more complex than it needs to be. Numéro de notice : C2009-062 Affiliation des auteurs : LAREG (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-20338-1_3 Date de publication en ligne : 01/01/2011 En ligne : https://doi.org/10.1007/978-3-642-20338-1_3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102020 
Titre : Improved constraints on models of glacial isostatic adjustment: A review of the contribution of ground-based geodetic observations Type de document : Article/Communication Auteurs : Matt A. King, Auteur ; Zuheir Altamimi Année de publication : 2010 Article en page(s) : pp 465 - 507 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Antarctique
[Termes IGN] bilan de masse
[Termes IGN] calotte glaciaire
[Termes IGN] champ de vitesse
[Termes IGN] données GRACE
[Termes IGN] Groenland
[Termes IGN] mesure géodésique
[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] rebond post-glaciaireRésumé : (auteur) The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA is uncertain due to insufficient constraints on our knowledge of past glacial changes and to large simplifications in the underlying Earth models. Consequently, we show differences between models that exceed several mm/year in terms of surface displacement for the two major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement offer the potential for new constraints to be made on GIA models, especially when they are used to improve structural features of the Earth’s interior as to allow for a more realistic reconstruction of the glaciation history. We present the distribution of presently available campaign and continuous geodetic measurements in Greenland and Antarctica and summarise surface velocities published to date, showing substantial disagreement between techniques and GIA models alike. We review the current state-of-the-art in ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise surface velocities. In particular, we focus on known areas of need in GPS observation level models and the terrestrial reference frame in order to advance geodetic observation precision/accuracy toward 0.1 mm/year and therefore further constrain models of GIA and subsequent present-day ice mass change estimates. Numéro de notice : A2010-663 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10712-010-9100-4 Date de publication en ligne : 16/06/2010 En ligne : https://doi.org/10.1007/s10712-010-9100-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91769
in Surveys in Geophysics > vol 31 n° 5 (September 2010) . - pp 465 - 507[article]Documents numériques
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Titre : A first look at the effects of ionospheric signal bending on a globally processed GPS network Type de document : Article/Communication Auteurs : E. Petrie, Auteur ; M. King, Auteur ; P. Moore, Auteur ; David Lavallée, Auteur Année de publication : 2010 Article en page(s) : pp 491 - 499 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal
[Termes IGN] atténuation du signal
[Termes IGN] correction ionosphérique
[Termes IGN] propagation ionosphérique
[Termes IGN] réfraction atmosphérique
[Termes IGN] retard troposphérique zénithal
[Termes IGN] signal GPSRésumé : (Auteur) This study provides a first attempt at quantifying potential signal bending effects on the GPS reference frame, coordinates and zenith tropospheric delays (ZTDs). To do this, we homogeneously reanalysed data from a global network of GPS sites spanning 14 years (1995.0–2009.0). Satellite, Earth orientation, tropospheric and ground station coordinate parameters were all estimated. We tested the effect of geometric bending and dTEC bending corrections, which were modelled at the observation level based, in part, on parameters from the International Reference Ionosphere 2007 model. Combined, the two bending corrections appear to have a minimal effect on site coordinates and ZTDs except for low latitude sites. Considering five days (DOY 301–305, 28 October–1 November 2001) near ionospheric maximum in detail, they affect mean ZTDs by up to ~1.7 mm at low latitudes, reducing to negligible levels at high latitudes. Examining the effect on coordinates in terms of power-spectra revealed the difference to be almost entirely white noise, with noise amplitude ranging from 0.3 mm (high latitudes) to 2.4 mm (low latitudes). The limited effect on station coordinates is probably due to the similarity in the elevation dependence of the bending term with that of tropospheric mapping functions. The smoothed z-translation from the GPS reference frame to ITRF2005 changes by less than 2 mm, though the effect combines positively with that from the second order ionospheric refractive index term. We conclude that, at the present time, and for most practical purposes, the geometric and dTEC bending corrections are probably negligible at current GPS/reference frame precisions. Numéro de notice : A2010-440 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0386-2 Date de publication en ligne : 01/06/2010 En ligne : https://doi.org/10.1007/s00190-010-0386-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30633
in Journal of geodesy > vol 84 n° 8 (August 2010) . - pp 491 - 499[article]Réservation
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