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On the assimilation of absolute geodetic dynamic topography in a global ocean model: impact on the deep ocean state / Alexey Androsov in Journal of geodesy, vol 93 n° 2 (February 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 2 (February 2019) . - pp 141 - 157 Titre : On the assimilation of absolute geodetic dynamic topography in a global ocean model: impact on the deep ocean state Type de document : Article/Communication Auteurs : Alexey Androsov, Auteur ; Lars Nerger, Auteur ; Reiner Schnur, Auteur ; Alberta Albertella, Auteur ; Reiner Rummel, Auteur ; et al., Auteur Année de publication : 2019 Article en page(s) : pp 141 - 157 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] assimilation des données [Termes IGN] circulation océanique [Termes IGN] données altimétriques [Termes IGN] données CHAMP [Termes IGN] données GOCE [Termes IGN] données GRACE [Termes IGN] filtre de Kalman [Termes IGN] geoïde marin [Termes IGN] géoïde terrestre [Termes IGN] hauteurs de mer [Termes IGN] modèle de simulation [Termes IGN] modèle océanographique [Termes IGN] océanographie dynamique [Termes IGN] salinité [Termes IGN] température de surface de la mer Résumé : (auteur) General ocean circulation models are not perfect. Forced with observed atmospheric fluxes they gradually drift away from measured distributions of temperature and salinity. We suggest data assimilation of absolute dynamical ocean topography (DOT) observed from space geodetic missions as an option to reduce these differences. Sea surface information of DOT is transferred into the deep ocean by defining the analysed ocean state as a weighted average of an ensemble of fully consistent model solutions using an error-subspace ensemble Kalman filter technique. Success of the technique is demonstrated by assimilation into a global configuration of the ocean circulation model FESOM over 1 year. The dynamic ocean topography data are obtained from a combination of multi-satellite altimetry and geoid measurements. The assimilation result is assessed using independent temperature and salinity analysis derived from profiling buoys of the AGRO float data set. The largest impact of the assimilation occurs at the first few analysis steps where both the model ocean topography and the steric height (i.e. temperature and salinity) are improved. The continued data assimilation over 1 year further improves the model state gradually. Deep ocean fields quickly adjust in a sustained manner: A model forecast initialized from the model state estimated by the data assimilation after only 1 month shows that improvements induced by the data assimilation remain in the model state for a long time. Even after 11 months, the modelled ocean topography and temperature fields show smaller errors than the model forecast without any data assimilation. Numéro de notice : A2019-076 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1151-1 Date de publication en ligne : 12/05/2018 En ligne : https://doi.org/10.1007/s00190-018-1151-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92190 [article]

The relation between degree-2160 spectral models of Earth’s gravitational and topographic potential : a guide on global correlation measures and their dependency on approximation effects / Christian Hirt in Journal of geodesy, vol 91 n° 10 (October 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 10 (October 2017) . - pp 1179 – 1205 Titre : The relation between degree-2160 spectral models of Earth’s gravitational and topographic potential : a guide on global correlation measures and their dependency on approximation effects Type de document : Article/Communication Auteurs : Christian Hirt, Auteur ; Moritz Rexer, Auteur ; Sten Claessens, Auteur ; Reiner Rummel, Auteur Année de publication : 2017 Article en page(s) : pp 1179 – 1205 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] corrélation [Termes IGN] Earth Gravity Model 2008 [Termes IGN] erreur systématique [Termes IGN] modèle de géopotentiel [Termes IGN] potentiel de pesanteur terrestre Résumé : (Auteur) Comparisons between high-degree models of the Earth’s topographic and gravitational potential may give insight into the quality and resolution of the source data sets, provide feedback on the modelling techniques and help to better understand the gravity field composition. Degree correlations (cross-correlation coefficients) or reduction rates (quantifying the amount of topographic signal contained in the gravitational potential) are indicators used in a number of contemporary studies. However, depending on the modelling techniques and underlying levels of approximation, the correlation at high degrees may vary significantly, as do the conclusions drawn. The present paper addresses this problem by attempting to provide a guide on global correlation measures with particular emphasis on approximation effects and variants of topographic potential modelling. We investigate and discuss the impact of different effects (e.g., truncation of series expansions of the topographic potential, mass compression, ellipsoidal versus spherical approximation, ellipsoidal harmonic coefficient versus spherical harmonic coefficient (SHC) representation) on correlation measures. Our study demonstrates that the correlation coefficients are realistic only when the model’s harmonic coefficients of a given degree are largely independent of the coefficients of other degrees, permitting degree-wise evaluations. This is the case, e.g., when both models are represented in terms of SHCs and spherical approximation (i.e. spherical arrangement of field-generating masses). Alternatively, a representation in ellipsoidal harmonics can be combined with ellipsoidal approximation. The usual ellipsoidal approximation level (i.e. ellipsoidal mass arrangement) is shown to bias correlation coefficients when SHCs are used. Importantly, gravity models from the International Centre for Global Earth Models (ICGEM) are inherently based on this approximation level. A transformation is presented that enables a transformation of ICGEM geopotential models from ellipsoidal to spherical approximation. The transformation is applied to generate a spherical transform of EGM2008 (sphEGM2008) that can meaningfully be correlated degree-wise with the topographic potential. We exploit this new technique and compare a number of models of topographic potential constituents (e.g., potential implied by land topography, ocean water masses) based on the Earth2014 global relief model and a mass-layer forward modelling technique with sphEGM2008. Different to previous findings, our results show very significant short-scale correlation between Earth’s gravitational potential and the potential generated by Earth’s land topography (correlation +0.92, and 60% of EGM2008 signals are delivered through the forward modelling). Our tests reveal that the potential generated by Earth’s oceans water masses is largely unrelated to the geopotential at short scales, suggesting that altimetry-derived gravity and/or bathymetric data sets are significantly underpowered at 5 arc-min scales. We further decompose the topographic potential into the Bouguer shell and terrain correction and show that they are responsible for about 20 and 25% of EGM2008 short-scale signals, respectively. As a general conclusion, the paper shows the importance of using compatible models in topographic/gravitational potential comparisons and recommends the use of SHCs together with spherical approximation or EHCs with ellipsoidal approximation in order to avoid biases in the correlation measures. Numéro de notice : A2017-541 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1016-z En ligne : https://doi.org/10.1007/s00190-017-1016-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86596 [article]

Global height system unification with GOCE: a simulation study on the indirect bias term in the GBVP approach / C. Gerlach in Journal of geodesy, vol 87 n° 1 (January 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 1 (January 2013) . - pp 57 - 67 Titre : Global height system unification with GOCE: a simulation study on the indirect bias term in the GBVP approach Type de document : Article/Communication Auteurs : C. Gerlach, Auteur ; Reiner Rummel, Auteur Année de publication : 2013 Article en page(s) : pp 57 - 67 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] altitude [Termes IGN] anomalie de pesanteur [Termes IGN] données GOCE [Termes IGN] erreur systématique [Termes IGN] géoïde gravimétrique [Termes IGN] géoïde terrestre [Termes IGN] harmonique sphérique [Termes IGN] hauteur ellipsoïdale [Termes IGN] modèle de géopotentiel [Termes IGN] problème des valeurs limites [Termes IGN] résidu [Termes IGN] système de référence altimétrique Résumé : (Auteur) One of the main objectives of ESA’s Gravity Field and Steady-State Ocean Circulation mission GOCE (Gravity field and steady-state ocean circulation mission, 1999) is to allow global unification of height systems by directly providing potential differences between benchmarks in different height datum zones. In other words, GOCE provides a globally consistent and unbiased geoid. If this information is combined with ellipsoidal (derived from geodetic space techniques) and physical heights (derived from leveling/gravimetry) at the same benchmarks, datum offsets between the datum zones can be determined and all zones unified. The expected accuracy of GOCE is around 2–3 cm up to spherical harmonic degree nmax ~ 200. The omission error above this degree amounts to about 30 cm which cannot be neglected. Therefore, terrestrial residual gravity anomalies are necessary to evaluate the medium and short wavelengths of the geoid, i.e. one has to solve the Geodetic Boundary Value Problem (GBVP). The theory of height unification by the GBVP approach is well developed, see e.g. Colombo (A World Vertical Network. Report 296, Department of Geodetic Science and Surveying, 1980) or Rummel and Teunissen (Bull Geod 62:477–498, 1988). Thereby, it must be considered that terrestrial gravity anomalies referring to different datum zones are biased due to the respective datum offsets. Consequently, the height reference surface of a specific datum zone deviates from the unbiased geoid not only due to its own datum offset (direct bias term) but is also indirectly affected by the integration of biased gravity anomalies. The latter effect is called the indirect bias term and it considerably complicates the adjustment model for global height unification. If no satellite based gravity model is employed, this error amounts to about the same size as the datum offsets, i.e. 1–2 m globally. We show that this value decreases if a satellite-only gravity model is used. Specifically for GOCE with nmax ~ 200, the error can be expected not to exceed the level of 1 cm, allowing the effect to be neglected in practical height unification. The results are supported by recent findings by Gatti et al. (J Geod, 2012). Numéro de notice : A2013-074 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0579-y En ligne : https://doi.org/10.1007/s00190-012-0579-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32212 [article]

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013011	SL	Revue	Centre de documentation	Revues en salle	Disponible

National report of the Federal Republic of Germany on the geodetic activities in the years 1999-2003 [for] XXIII [23rd] general assembly of the International Union for Geodesy and Geophysics (IUGG) 2003 in Sapporo, Japan / B. Heck (2003)

Public Titre : National report of the Federal Republic of Germany on the geodetic activities in the years 1999-2003 [for] XXIII [23rd] general assembly of the International Union for Geodesy and Geophysics (IUGG) 2003 in Sapporo, Japan Type de document : Rapport Auteurs : B. Heck, Éditeur scientifique ; Reiner Rummel, Éditeur scientifique ; Helmut Hornik, Éditeur scientifique Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2003 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 312 Importance : 124 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8592-3 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] activité géodésique [Termes IGN] champ de pesanteur terrestre [Termes IGN] géodésie spatiale [Termes IGN] géodynamique [Termes IGN] géopositionnement [Termes IGN] modélisation [Termes IGN] République fédérale d'Allemagne Note de contenu : Section I : Positioning Section Il : Advanced space technology Section III : Determination of the gravity field Section IV : General theory and methodology Section V : Geodynamics Numéro de notice : 13159 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=40396

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
13159-01	CG2003	Livre	Centre de documentation	Congrès	Disponible

National report of the Federal Republic of Germany on the geodetic activities in the years 1995 - 1999 / B. Heck (1999)

Public Titre : National report of the Federal Republic of Germany on the geodetic activities in the years 1995 - 1999 : XXII [22] general assembly of the International Union for Geodesy and Geophysics (IUGG) 1999 in Birmingham Type de document : Rapport Auteurs : B. Heck, Auteur ; Reiner Rummel, Auteur ; Erwin Groten, Auteur ; Helmut Hornik, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 1999 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 308 Importance : 124 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8588-6 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] activité géodésique [Termes IGN] champ de pesanteur terrestre [Termes IGN] géodésie spatiale [Termes IGN] géodynamique [Termes IGN] géopositionnement [Termes IGN] modélisation [Termes IGN] problème des valeurs limites [Termes IGN] République fédérale d'Allemagne Note de contenu : Section 1: Positioning Positioning - Overview and highlights H. DREWES Permanent GPS networks and reai-time positioning W. SCHLÜTER, K. PAHLER Positioning for global and long range applications W. SCHLÜTER, E. REINHART, K. PAHLER Positioning for close range and engineering application B. WITTE With contributions by M. BAUMKER, H.-P. FITZEN and E. GROTEN Section Il : Advanced space technology Advanced space technology - Overview and highlights R. RUMMEL Space observation instrumentation and satellite systems CH. REIGBER Spaceborne atmospheric monitoring R. KÔNIG Satellite orbit modelling J. DOW Section III : Determination of the gravity field Determination of the gravity field - Overview and highlights G. BOEDECKER Absolute and relative gravimetry M. BECKER Kinematic gravimetry G.W. HEIN Global gravity field modelling T. GRUBER Regional and local gravity field modelling H. DENKER Section IV : General theory and methodology Physical aspects of modeling in geodesy - Overview and highlights B. HECK Physical aspects of modelling in geodesy E. GRAFAREND Mathematical aspects of modelling K.H. ILK Theory of data évaluation S. MEIER Section V : Geodynamics Recent crustai movements and déformations W. AUGATH Tides and other temporal variations of the gravity field B. RICHTER Sea level and ice sheet variations R. DIETRICH Earth rotation variation and its geodynamic causes E. GROTEN Editors' and authors' address list Numéro de notice : 61213 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=44230

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
61213-01	CG.99	Livre	Centre de documentation	Congrès	Disponible

European views on dedicated gravity field missions / Georges Balmino (1998)

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Spherical harmonic analysis of satellite gradiometry / Reiner Rummel (1993)  

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A quality investigation of global vertical datum connection / Xu Peiliang (1991)  

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Gravity, gradiometry and gravimetry, IAG Symposium, Edinburgh, 1989 / Reiner Rummel (1990)  

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A model comparison in least squares collocation / Reiner Rummel (1976)

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Downward continuation of gravity information from satellite to satellite tracking or satellite gradiometry in local areas / Reiner Rummel (1975)

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Methods for the computation of detailed geoids and their accuracy / R.H. Rapp (1975)

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Variationen zum Geoid in Deutschland / J. Brennecke (1975)

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Zur Behandlung von Zufallsfunktionen und -folgen in der physikalischen Geodäsie / Reiner Rummel (1975)

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