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Optima multi-step collocation: application to the space-wise approach for GOCE data analysis / M. Reguzzoni in Journal of geodesy, vol 83 n° 1 (January 2009)  

Public [article]  inJournal of geodesy > vol 83 n° 1 (January 2009) . - pp 13 - 29 Titre : Optima multi-step collocation: application to the space-wise approach for GOCE data analysis Type de document : Article/Communication Auteurs : M. Reguzzoni, Auteur ; N. Tselfes, Auteur Année de publication : 2009 Article en page(s) : pp 13 - 29 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse harmonique [Termes IGN] champ de pesanteur terrestre [Termes IGN] coefficient de géopotentiel [Termes IGN] collocation [Termes IGN] GOCE [Termes IGN] harmonique sphérique [Termes IGN] levé gravimétrique Résumé : (Auteur) Collocation is widely used in physical geodesy. Its application requires to solve systems with a dimension equal to the number of observations, causing numerical problems when many observations are available. To overcome this drawback, tailored step-wise techniques are usually applied. An example of these step-wise techniques is the space-wise approach to the GOCE mission data processing. The original idea of this approach was to implement a two-step procedure, which consists of first predicting gridded values at satellite altitude by collocation and then deriving the geo-potential spherical harmonic coefficients by numerical integration. The idea was generalized to a multi-step iterative procedure by introducing a time-wise Wiener filter to reduce the highly correlated observation noise. Recent studies have shown how to optimize the original two-step procedure, while the theoretical optimization of the full multi-step procedure is investigated in this work. An iterative operator is derived so that the final estimated spherical harmonic coefficients are optimal with respect to the Wiener–Kolmogorov principle, as if they were estimated by a direct collocation. The logical scheme used to derive this optimal operator can be applied not only in the case of the space-wise approach but, in general, for any case of step-wise collocation. Several numerical tests based on simulated realistic GOCE data are performed. The results show that adding a pre-processing time-wise filter to the two-step procedure of data gridding and spherical harmonic analysis is useful, in the sense that the accuracy of the estimated geo-potential coefficients is improved. This happens because, in its practical implementation, the gridding is made by collocation over local patches of data, while the observation noise has a time-correlation so long that it cannot be treated inside the patch size. Therefore, the multi-step operator, which is in theory equivalent to the two-step operator and to the direct collocation, is in practice superior thanks to the time-wise filter that reduces the noise correlation before the gridding. The criteria for the choice of this filter are investigated numerically. Copyright Springer Numéro de notice : A2009-179 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-008-0225-x En ligne : https://doi.org/10.1007/s00190-008-0225-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29809 [article]

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266-09012	RAB	Revue	Centre de documentation	En réserve L003	Disponible

A study reference frame consistency in recent Earth gravitational models / Christopher Kotsakis in Journal of geodesy, vol 83 n° 1 (January 2009)  

Public [article]  inJournal of geodesy > vol 83 n° 1 (January 2009) . - pp 31 - 50 Titre : A study reference frame consistency in recent Earth gravitational models Type de document : Article/Communication Auteurs : Christopher Kotsakis, Auteur Année de publication : 2009 Article en page(s) : pp 31 - 50 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] cohérence des données [Termes IGN] Earth Gravity Model 2008 [Termes IGN] GRACE [Termes IGN] harmonique sphérique [Termes IGN] levé gravimétrique [Termes IGN] modèle de géopotentiel [Termes IGN] repère de référence Résumé : (Auteur) All gravity field functionals obtained from an Earth gravitational model (EGM) depend on the underlying terrestrial reference frame (TRF), with respect to which the EGM’s spherical harmonic coefficients refer to. In order to maintain a coherent framework for the comparison of current and future EGMs, it is thus important to investigate the consistency of their inherent TRFs, especially when their use is intended for high precision studies. Following the methodology described in an earlier paper by Kleusberg (1980), the similarity transformation parameters between the associated reference frames for several EGMs (including the most recent CHAMP/GRACE models at the time of writing this paper) are estimated in the present study. Specifically, the differences between the spherical harmonic coefficients for various pairs of EGMs are parameterized through a 3D-similarity spatial transformation model that relates their underlying TRFs. From the least-squares adjustment of such a parametric model, the origin, orientation and scale stability between the EGMs’ reference frames can be identified by estimating their corresponding translation, rotation and scale factor parameters. Various aspects of the estimation procedure and its results are highlighted in the paper, including data weighting schemes, the sensitivity of the results with respect to the selected harmonic spectral band, the correlation structure and precision level of the estimated transformation parameters, the effect of the estimated differences of the EGMs’ reference frames on their height anomaly signal, and the overall feasibility of Kleusberg’s formulae for the assessment of TRF inconsistencies among global geopotential models. Copyright Springer Numéro de notice : A2009-180 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-008-0227-8 En ligne : https://doi.org/10.1007/s00190-008-0227-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29810 [article]

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266-09012	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Consideration of time-correlated errors in a Kalman filter applicable to GNSS / M.G. Potovello in Journal of geodesy, vol 83 n° 1 (January 2009)  

Public [article]  inJournal of geodesy > vol 83 n° 1 (January 2009) . - pp 51 - 56 Titre : Consideration of time-correlated errors in a Kalman filter applicable to GNSS Type de document : Article/Communication Auteurs : M.G. Potovello, Auteur ; Kyle O'Keefe, Auteur ; Gérard Lachapelle, Auteur ; M.E. Cannon, Auteur Année de publication : 2009 Article en page(s) : pp 51 - 56 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] bruit blanc [Termes IGN] covariance [Termes IGN] erreur corrélée au temps [Termes IGN] filtre de Kalman [Termes IGN] GPS en mode cinématique [Termes IGN] GPS en mode différentiel [Termes IGN] positionnement par GNSS [Termes IGN] traitement différé [Termes IGN] traitement du signal Résumé : (Auteur) An algorithm for considering time-correlated errors in a Kalman filter is presented. The algorithm differs from previous implementations in that it does not suffer from numerical problems; does not contain inherent time latency or require reinterpretation of Kalman filter parameters, and gives full consideration to additive white noise that is often still present but ignored in previous implementations. Simulation results indicate that the application of the new algorithm yields more realistic and therefore useful state and covariance information than the standard implementation. Results from a field test of the algorithm applied to the problem of kinematic differential GPS demonstrate that the algorithm provides slightly pessimistic covariance estimates whereas the standard Kalman filter provides optimistic covariance estimates. Copyright Springer Numéro de notice : A2009-181 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-008-0231-z En ligne : https://doi.org/10.1007/s00190-008-0231-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29811 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-09011	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-09012	RAB	Revue	Centre de documentation	En réserve L003	Disponible