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On the detectability of synthetic disturbances in FG5 absolute gravimetry data using lomb-scargle analysis / M. Orlob in Geomatica, vol 66 n° 2 (June 2012)
[article]
Titre : On the detectability of synthetic disturbances in FG5 absolute gravimetry data using lomb-scargle analysis Type de document : Article/Communication Auteurs : M. Orlob, Auteur ; Alexander Braun, Auteur Année de publication : 2012 Article en page(s) : pp 113 - 124 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] gravimètre absolu
[Termes IGN] levé gravimétrique
[Termes IGN] rapport signal sur bruit
[Termes IGN] résidu
[Termes IGN] transformation de FourierRésumé : (Auteur) Une perturbation attribuable aux instruments ou à l’environnement (signal et bruit) dans les observations du gravimètre absolu FG5 devient visible en analysant les résiduelles, qui représentent les écarts relativement à la parabole d’accélération théorique. Même si l’analyse spectrale des résiduelles du FG5 par la transformée de Fourier discrète (TFD) classique est limitée par la nature inégale de l’espacement des observations par FG5, le périodogramme Lomb-Scargle peut analyser des observations inégalement espacées et estimer (détecter) des signaux dans les résiduelles du FG5. Nous étudions le caractère détectable des perturbations introduites synthétiquement dans les résiduelles du FG5 au moyen de l’analyse du périodogramme Lomb-Scargle. La sensibilité du processus de mesure et d’ajustement du FG5 est fonction de la fréquence, de l’amplitude, de la phase et du rapport signal-bruit (S/B) des perturbations. Nous concluons que la longueur de chute libre utilisée et la fonction de transfert de l’instrument peuvent modifier considérablement les valeurs de gravité estimées. En outre, nous établissons une fonction de sensibilité appelée LOFSMAP, qui dépend de l’espace de paramètre de la perturbation que sont l’amplitude, la fréquence, la phase et le rapport S/B. Numéro de notice : A2012-503 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.5623/cig2012-024 En ligne : https://doi.org/10.5623/cig2012-024 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31949
in Geomatica > vol 66 n° 2 (June 2012) . - pp 113 - 124[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 035-2012021 RAB Revue Centre de documentation En réserve L003 Disponible The effect of using inconsistent ocean tidal loading models on GPS coordinate solutions / Y. Fu in Journal of geodesy, vol 86 n° 6 (June 2012)
[article]
Titre : The effect of using inconsistent ocean tidal loading models on GPS coordinate solutions Type de document : Article/Communication Auteurs : Y. Fu, Auteur ; J. Freymueller, Auteur ; Tonie M. van Dam, Auteur Année de publication : 2012 Article en page(s) : pp 409 - 421 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] coordonnées GPS
[Termes IGN] géocentre
[Termes IGN] masse de la Terre
[Termes IGN] surcharge océaniqueRésumé : (Auteur) We use up to a 6-year span of GPS data from 85 globally distributed stations to compare solutions using ocean tidal loading (OTL) corrections computed in different reference frames: center of mass of the solid Earth (CE), and center of mass of the Earth system (CM). We compare solution sets that differ only in the frame used for the OTL model computations, for three types of GPS solutions. In global solutions with all parameters including orbits estimated simultaneously, we find coordinate differences of ~0.3 mm between solutions using OTL computed in CM and OTL computed in CE. When orbits or orbits and clocks are fixed, larger biases appear if the user applies an OTL model inconsistent with that used to derive the orbit and clock products. Network solutions (orbits fixed, satellite clocks estimated) show differences smaller than 0.5 mm due to model inconsistency, but PPP solutions show distortions at the ~1.3 mm level. The much larger effect on PPP solutions indicates that satellite clock estimates are sensitive to the OTL model applied. The time series of coordinate differences shows a strong spectral peak at a period of ~14 days when inconsistent OTL models are applied and smaller peaks at ~annual and ~semi-annual periods, for both ambiguity-free and ambiguity-fixed solutions. These spurious coordinate variations disappear in solutions using consistent OTL models. Users of orbit and clock products must ensure that they use OTL coefficients computed in the same reference frame as the OTL coefficients used by the analysis centers that produced the products they use; otherwise, systematic errors will be introduced into position solutions. All modern products should use loading models computed in the CM frame, but legacy products may require loading models computed in the CE frame. Analysts and authors need to document the frame used for all loading computations in product descriptions and papers. Numéro de notice : A2012-243 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0528-1 Date de publication en ligne : 23/11/2011 En ligne : https://doi.org/10.1007/s00190-011-0528-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31689
in Journal of geodesy > vol 86 n° 6 (June 2012) . - pp 409 - 421[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2012061 RAB Revue Centre de documentation En réserve L003 Disponible Wavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations / M. Hayn in Geophysical journal international, vol 189 n° 3 (June 2012)
[article]
Titre : Wavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations Type de document : Article/Communication Auteurs : M. Hayn, Auteur ; Isabelle Panet , Auteur ; Michel Diament , Auteur ; Matthias Holschneider, Auteur ; Mioara Mandea, Auteur ; Anne Davaille Année de publication : 2012 Article en page(s) : pp 1430 - 1456 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] anomalie de pesanteur
[Termes IGN] données GRACE
[Termes IGN] manteau terrestre
[Termes IGN] modèle de géopotentiel
[Termes IGN] ondelette d'Abel-Poisson
[Termes IGN] Pacifique (océan)
[Termes IGN] subduction
[Termes IGN] transformation en ondelettesRésumé : (Auteur) In the eighties, the analysis of satellite altimetry data leads to the major discovery of gravity lineations in the oceans, with wavelengths between 200 and 1400 km. While the existence of the 200 km scale undulations is widely accepted, undulations at scales larger than 400 km are still a matter of debate. In this paper, we revisit the topic of the large‐scale geoid undulations over the oceans in the light of the satellite gravity data provided by the GRACE mission, considerably more precise than the altimetry data at wavelengths larger than 400 km.
First, we develop a dedicated method of directional Poisson wavelet analysis on the sphere with significance testing, in order to detect and characterize directional structures in geophysical data on the sphere at different spatial scales. This method is particularly well suited for potential field analysis. We validate it on a series of synthetic tests, and then apply it to analyze recent gravity models, as well as a bathymetry data set independent from gravity. Our analysis confirms the existence of gravity undulations at large scale in the oceans, with characteristic scales between 600 and 2000 km. Their direction correlates well with present‐day plate motion over the Pacific ocean, where they are particularly clear, and associated with a conjugate direction at 1500 km scale. A major finding is that the 2000 km scale geoid undulations dominate and had never been so clearly observed previously. This is due to the great precision of GRACE data at those wavelengths. Given the large scale of these undulations, they are most likely related to mantle processes. Taking into account observations and models from other geophysical information, as seismological tomography, convection and geochemical models and electrical conductivity in the mantle, we conceive that all these inputs indicate a directional fabric of the mantle flows at depth, reflecting how the history of subduction influences the organization of lower mantle upwellings.Numéro de notice : A2012-742 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2012.05455.x Date de publication en ligne : 19/04/2012 En ligne : https://doi.org/10.1111/j.1365-246X.2012.05455.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91491
in Geophysical journal international > vol 189 n° 3 (June 2012) . - pp 1430 - 1456[article]Estimating geoid height change in North America: past, present and future / T. Jacob in Journal of geodesy, vol 86 n° 5 (May 2012)
[article]
Titre : Estimating geoid height change in North America: past, present and future Type de document : Article/Communication Auteurs : T. Jacob, Auteur ; John Wahr, Auteur ; R. Gross, Auteur ; S. Swenson, Auteur ; A. Geruo, Auteur Année de publication : 2012 Article en page(s) : pp 337 - 358 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] Amérique du nord
[Termes IGN] champ de pesanteur local
[Termes IGN] données GRACE
[Termes IGN] éruption volcanique
[Termes IGN] Etats-Unis
[Termes IGN] géoïde gravimétrique
[Termes IGN] géoïde local
[Termes IGN] surveillance géologiqueRésumé : (Auteur) The forthcoming GRAV-D gravimetric geoid model over the United States is to be updated regularly to account for changes in geoid height. Its baseline precision is to be at the 10–20 mm level over non-mountainous regions. The aim of this study is to provide an estimate of the magnitude, time scale, and spatial footprint of geoid height change over North America, from mass redistribution processes of hydrologic, cryospheric and solid Earth nature. Geoid height changes from continental water storage changes over the past 50 years and predicted over the next century are evaluated and are highly dependent on the used model. Groundwater depletion from anthropogenic pumping in regional scale aquifers may lead to geoid changes of 10 mm magnitude every 50–100 years. The GRACE time varying gravity fields are used to (I) assess the errors in a glacial isostatic adjustment model, which, if used to correct the GRAV-D model, may induce errors at the 10 mm geoid height level after ~20 years, (II), evaluate geoid height change over ice mass loss regions of North America, which, if they remain unchanged in the future, may lead to geoid height changes at the 10 mm level in under a decade and (III), compute sea level rise and its effect on the geoid, which is found to be negligible. Coseismic gravitational changes from past North American earthquakes are evaluated, and lead to geoid change at the 10-mm level for only the largest thrust earthquakes. Finally, geoid change from volcanic processes are assessed and found to be significant with respect to the GRAV-D geoid model baseline precision for cataclysmic events, such as that of the 1980 Mt. St. Helens eruption. Recommendations on how to best monitor geoid change in the future are given. Numéro de notice : A2012-242 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0522-7 Date de publication en ligne : 01/11/2011 En ligne : https://doi.org/10.1007/s00190-011-0522-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31688
in Journal of geodesy > vol 86 n° 5 (May 2012) . - pp 337 - 358[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2012051 RAB Revue Centre de documentation En réserve L003 Disponible Simulation study of a follow-on gravity mission to GRACE / B. Loomis in Journal of geodesy, vol 86 n° 5 (May 2012)
[article]
Titre : Simulation study of a follow-on gravity mission to GRACE Type de document : Article/Communication Auteurs : B. Loomis, Auteur ; R. Nerem, Auteur ; Scott B. Luthcke, Auteur Année de publication : 2012 Article en page(s) : pp 319 - 335 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] crénelage
[Termes IGN] données GRACE
[Termes IGN] masse de la Terre
[Termes IGN] simulationRésumé : (Auteur) The gravity recovery and climate experiment (GRACE) has been providing monthly estimates of the Earth’s time-variable gravity field since its launch in March 2002. The GRACE gravity estimates are used to study temporal mass variations on global and regional scales, which are largely caused by a redistribution of water mass in the Earth system. The accuracy of the GRACE gravity fields are primarily limited by the satellite-to-satellite range-rate measurement noise, accelerometer errors, attitude errors, orbit errors, and temporal aliasing caused by un-modeled high-frequency variations in the gravity signal. Recent work by Ball Aerospace & Technologies Corp., Boulder, CO has resulted in the successful development of an interferometric laser ranging system to specifically address the limitations of the K-band microwave ranging system that provides the satellite-to-satellite measurements for the GRACE mission. Full numerical simulations are performed for several possible configurations of a GRACE Follow-On (GFO) mission to determine if a future satellite gravity recovery mission equipped with a laser ranging system will provide better estimates of time-variable gravity, thus benefiting many areas of Earth systems research. The laser ranging system improves the range-rate measurement precision to ~0.6 nm/s as compared to ~0.2 ?m/s for the GRACE K-band microwave ranging instrument. Four different mission scenarios are simulated to investigate the effect of the better instrument at two different altitudes. The first pair of simulated missions is flown at GRACE altitude (~480 km) assuming on-board accelerometers with the same noise characteristics as those currently used for GRACE. The second pair of missions is flown at an altitude of ~250 km which requires a drag-free system to prevent satellite re-entry. In addition to allowing a lower satellite altitude, the drag-free system also reduces the errors associated with the accelerometer. All simulated mission scenarios assume a two satellite co-orbiting pair similar to GRACE in a near-polar, near-circular orbit. A method for local time variable gravity recovery through mass concentration blocks (mascons) is used to form simulated gravity estimates for Greenland and the Amazon region for three GFO configurations and GRACE. Simulation results show that the increased precision of the laser does not improve gravity estimation when flown with on-board accelerometers at the same altitude and spacecraft separation as GRACE, even when time-varying background models are not included. This study also shows that only modest improvement is realized for the best-case scenario (laser, low-altitude, drag-free) as compared to GRACE due to temporal aliasing errors. These errors are caused by high-frequency variations in the hydrology signal and imperfections in the atmospheric, oceanographic, and tidal models which are used to remove unwanted signal. This work concludes that applying the updated technologies alone will not immediately advance the accuracy of the gravity estimates. If the scientific objectives of a GFO mission require more accurate gravity estimates, then future work should focus on improvements in the geophysical models, and ways in which the mission design or data processing could reduce the effects of temporal aliasing. Numéro de notice : A2012-241 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0521-8 Date de publication en ligne : 28/10/2011 En ligne : https://doi.org/10.1007/s00190-011-0521-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31687
in Journal of geodesy > vol 86 n° 5 (May 2012) . - pp 319 - 335[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2012051 RAB Revue Centre de documentation En réserve L003 Disponible The US Gravimetric Geoid of 2009 (USGG2009): model development and evaluation / Y. Wang in Journal of geodesy, vol 86 n° 3 (March 2012)PermalinkHigh precision levelling supporting the International Comparison of Absolute Gravimeters / Z. Jiang in Metrologia, vol 49 n° 1 (February 2012)PermalinkRelative gravity measurement campaign during the 8th international comparison of absolute gravimeters (2009) / Z. Jiang in Metrologia, vol 49 n° 1 (February 2012)PermalinkPermalinkPermalinkA dense global velocity field based on GNSS observations: Preliminary Results / Carine Bruyninx (2012)PermalinkDétermination du champ de pesanteur par gradiométrie spatiale [diaporama] / Gwendoline Pajot-Métivier (2012)PermalinkEntwicklung eines Kalman-Filters zur Bestimmung kurzzeitiger Variationen des Erdschwerefeldes aus daten der Satellitenmission GRACE / E. Kurtenbach (2012)PermalinkFlexible dataset combination and modelling by domain decomposition approaches / Isabelle Panet (2012)PermalinkPermalink