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On the accuracy assessment of celestial reference frame realizations / Z. Malkin in Journal of geodesy, vol 82 n° 6 (June 2008)  

Public [article]  inJournal of geodesy > vol 82 n° 6 (June 2008) . - pp 325 - 329 Titre : On the accuracy assessment of celestial reference frame realizations Type de document : Article/Communication Auteurs : Z. Malkin, Auteur Année de publication : 2008 Article en page(s) : pp 325 - 329 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] données ITGB [Termes IGN] estimation de précision [Termes IGN] précision des données [Termes IGN] repère de référence céleste [Termes IGN] système de référence céleste Résumé : (Auteur) The scatter of the celestial pole offset (CPO) time-series obtained from very long baseline interferometry (VLBI) observations is used as a measure of the accuracy of celestial reference frame (CRF) realizations. Several scatter indices (SI), including some proposed for the first time, are investigated. The first SI is based on residual analysis of CPO series with respect to a free core nutation (FCN) model. The second group of SIs includes Allan deviation and its extensions, which allow the treatment of unequally weighted and multidimensional observations. Application of these criteria to several radio source catalogues (RSCs) showed their ability to perform a preliminary assessment of the quality of each RSC. The 2D Allan deviation estimate seems to be the most sensitive measure. The proposed extensions of Allan deviation, weighted and multidimensional, can also be used for the statistical analysis of other time-series. Copyright Springer Numéro de notice : A2008-314 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0181-x En ligne : https://doi.org/10.1007/s00190-007-0181-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29307 [article]

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Ocean tide loading (OTL) displacements from global and local grids: comparisons to GPS estimates over the shelf of Brittany, France / Stavros A. Melachroinos in Journal of geodesy, vol 82 n° 6 (June 2008)  

Public [article]  inJournal of geodesy > vol 82 n° 6 (June 2008) . - pp 357 - 371 Titre : Ocean tide loading (OTL) displacements from global and local grids: comparisons to GPS estimates over the shelf of Brittany, France Type de document : Article/Communication Auteurs : Stavros A. Melachroinos, Auteur ; Richard Biancale, Auteur ; Muriel Llubes, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 357 - 371 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] baie [Termes IGN] Bretagne [Termes IGN] Cotentin [Termes IGN] marée océanique [Termes IGN] modèle physique [Termes IGN] Mont-Saint-Michel [Termes IGN] plateau continental [Termes IGN] positionnement par GPS [Termes IGN] série temporelle [Termes IGN] surcharge océanique [Termes IGN] trajet multiple Résumé : (Auteur) In this paper we examine OTL displacements detected by GPS stations of a dedicated campaign and validate ocean tide models. Our area of study is the continental shelf of Brittany and Cotentin in France. Brittany is one of the few places in the world where tides provoke loading displacements of ?10–12 cm vertically and a few cm horizontally. Ocean tide models suffer from important discrepancies in this region. Seven global and regional ocean tide models were tested: FES2004 corrected for K2, TPXO.7.0, TPXO.6.2, GOT00.2, CSR4.0, NAO.99b and the most recent regional grids of the North East Atlantic (NEA2004). These gridded amplitudes and phases of ocean tides were convolved in order to get the predicted OTL displacements using two different algorithms. Data over a period of 3.5 months of 8 GPS campaign stations located on the north coast of Brittany are used, in order to evaluate the geographical distribution of the OTL effect. We have modified and implemented new algorithms in our GPS software, GINS 7.1. GPS OTL constituents are estimated based on 1-day batch solutions. We compare the observed GPS OTL constituents of M2, S2, N2 and K1 waves with the selected ocean tide models on global and regional grids. Large phase-lag and amplitude discrepancies over 20° and 1.5 cm in the vertical direction in the semi-diurnal band of M2 between predictions and GPS/models are detected in the Bay of Mont St-Michel. From a least squares spectral analysis of the GPS time-series, significant harmonic peaks in the integer multiples of the orbital periods of the GPS satellites are observed, indicating the existence of multipath effects in the GPS OTL constituents. The GPS OTL observations agree best with FES2004, NEA2004, GOT00.2 and CSR4.0 tide models. Copyright Springer Numéro de notice : A2008-315 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0185-6 En ligne : https://doi.org/10.1007/s00190-007-0185-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29308 [article]

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On the multivariate total least-squares approach to empirical coordinate transformations: three algorithms / Burkhard Schaffrin in Journal of geodesy, vol 82 n° 6 (June 2008)  

Public [article]  inJournal of geodesy > vol 82 n° 6 (June 2008) . - pp 373 - 383 Titre : On the multivariate total least-squares approach to empirical coordinate transformations: three algorithms Type de document : Article/Communication Auteurs : Burkhard Schaffrin, Auteur ; Yaron Felus, Auteur Année de publication : 2008 Article en page(s) : pp 373 - 383 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] analyse multivariée [Termes IGN] méthode des moindres carrés [Termes IGN] modèle linéaire [Termes IGN] transformation de coordonnées Résumé : (Auteur) The multivariate total least-squares (MTLS) approach aims at estimating a matrix of parameters, ?, from a linear model (Y-E Y = (X-E X ) · ?) that includes an observation matrix, Y, another observation matrix, X, and matrices of randomly distributed errors, E Y and E X . Two special cases of the MTLS approach include the standard multivariate least-squares approach where only the observation matrix, Y, is perturbed by random errors and, on the other hand, the data least-squares approach where only the coefficient matrix X is affected by random errors. In a previous contribution, the authors derived an iterative algorithm to solve the MTLS problem by using the nonlinear Euler–Lagrange conditions. In this contribution, new lemmas are developed to analyze the iterative algorithm, modify it, and compare it with a new ‘closed form’ solution that is based on the singular-value decomposition. For an application, the total least-squares approach is used to estimate the affine transformation parameters that convert cadastral data from the old to the new Israeli datum. Technical aspects of this approach, such as scaling the data and fixing the columns in the coefficient matrix are investigated. This case study illuminates the issue of “symmetry” in the treatment of two sets of coordinates for identical point fields, a topic that had already been emphasized by Teunissen (1989, Festschrift to Torben Krarup, Geodetic Institute Bull no. 58, Copenhagen, Denmark, pp 335–342). The differences between the standard least-squares and the TLS approach are analyzed in terms of the estimated variance component and a first-order approximation of the dispersion matrix of the estimated parameters. Copyright Springer Numéro de notice : A2008-316 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0186-5 En ligne : https://doi.org/10.1007/s00190-007-0186-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29309 [article]

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