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Devising stable geometrical reference frames for use in geodetic studies of vertical crustal motion / Michael Bevis in Journal of geodesy, vol 87 n° 4 (April 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 4 (April 2013) . - pp 311 - 321 Titre : Devising stable geometrical reference frames for use in geodetic studies of vertical crustal motion Type de document : Article/Communication Auteurs : Michael Bevis, Auteur ; Abel Brown, Auteur ; Eric Kendrick, Auteur Année de publication : 2013 Article en page(s) : pp 311 - 321 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] positionnement par GPS [Termes IGN] repère de référence Résumé : (Auteur) We present a method for constructing and assessing the stability of a geometrical reference frame for use in vertical crustal motion studies. Our approach exploits the fact that when we transform GPS velocity solutions from one reference frame (RF) to another one using a Helmert transformation, only the frame translation rate parameters produce significant changes in the vertical station velocities expressed in the final RF. Loosely speaking, one can select and impose a ‘vertical RF’ from an ensemble of candidate frames, without any reference to the ‘horizontal RF’ (which can be selected and imposed afterwards), by seeing how the frame translation rates vary as one moves across the ensemble of frames. We order this ensemble according to the number of stations, N, incorporated into the set VREF whose RMS vertical motion is minimized in order to realize each frame. The value of N controls the level of scatter in, and hence the degree of similarity between the vertical velocities of the stations composing VREF. We characterize a specific vertical RF as stable if all of the frames located in a large neighborhood of the ensemble which includes the specific frame are characterized by very small relative frame translation rates. In this case, the expression of vertical GPS station velocities in any of these frames would lead to very similar results. We present a case study using a very large global time series in which we find a large RF neighborhood in which vertical station velocities are globally stable at the ? 0.2 mm/year level, and a slightly smaller neighborhood in which vertical stability improves to ? 0.1 mm/year level in polar regions. Numéro de notice : A2013-216 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0600-5 Date de publication en ligne : 03/11/2012 En ligne : https://doi.org/10.1007/s00190-012-0600-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32354 [article]

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A continuous velocity field for Norway / Halfdan Pascal Kierulf in Journal of geodesy, vol 87 n° 4 (April 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 4 (April 2013) . - pp 337 - 349 Titre : A continuous velocity field for Norway Type de document : Article/Communication Auteurs : Halfdan Pascal Kierulf, Auteur ; Mohammed Ouassou, Auteur ; Matthew Simpson, Auteur ; Olav Vestol, Auteur Année de publication : 2013 Article en page(s) : pp 337 - 349 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] champ de vitesse [Termes IGN] krigeage [Termes IGN] Norvège [Termes IGN] positionnement par GNSS [Termes IGN] quantité continue Résumé : (Auteur) In Norway, as in the rest of Fennoscandia, the process of Glacial Isostatic Adjustment causes ongoing crustal deformation. The vertical and horizontal movements of the Earth can be measured to a high degree of precision using GNSS. The Norwegian GNSS network has gradually been established since the early 1990s and today contains approximately 140 stations. The stations are established both for navigation purposes and for studies of geophysical processes. Only a few of these stations have been analyzed previously. We present new velocity estimates for the Norwegian GNSS network using the processing package GAMIT. We examine the relation between time-series length and precision. With approximately 3.5 years of data, we are able to reproduce the secular vertical rate with a precision of 0.5 mm/year. To establish a continuous crustal velocity field in areas where we have no GNSS receivers or the observation period is too short to obtain reliable results, either interpolation or modeling is required. We experiment with both approaches in this analysis by using (i) a statistical interpolation method called Kriging and (ii) a GIA forward model. In addition, we examine how our vertical velocity field solution is affected by the inclusion of data from repeated leveling. Results from our geophysical model give better estimates on the edge of the network, but inside the network the statistical interpolation method performs better. In general, we find that if we have less than 3.5 years of data for a GNSS station, the interpolated value is better than the velocity estimate based on a single time-series. Numéro de notice : A2013-217 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0603-2 Date de publication en ligne : 09/11/2012 En ligne : https://doi.org/10.1007/s00190-012-0603-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32355 [article]

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Fast error analysis of continuous GNSS observations with missing data / M.S. Bos in Journal of geodesy, vol 87 n° 4 (April 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 4 (April 2013) . - pp 351 - 360 Titre : Fast error analysis of continuous GNSS observations with missing data Type de document : Article/Communication Auteurs : M.S. Bos, Auteur ; R. Fernandes, Auteur ; S. Williams, Auteur ; Luisa Bastos, Auteur Année de publication : 2013 Article en page(s) : pp 351 - 360 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] bruit (théorie du signal) [Termes IGN] classification par maximum de vraisemblance [Termes IGN] données GNSS [Termes IGN] matrice de covariance [Termes IGN] série temporelle [Termes IGN] traitement de données GNSS Résumé : (Auteur) One of the most widely used method for the time-series analysis of continuous Global Navigation Satellite System (GNSS) observations is Maximum Likelihood Estimation (MLE) which in most implementations requires O(n3) operations for n observations. Previous research by the authors has shown that this amount of operations can be reduced to O(n2) for observations without missing data. In the current research we present a reformulation of the equations that preserves this low amount of operations, even in the common situation of having some missing data. Our reformulation assumes that the noise is stationary to ensure a Toeplitz covariance matrix. However, most GNSS time-series exhibit power-law noise which is weakly non-stationary. To overcome this problem, we present a Toeplitz covariance matrix that provides an approximation for power-law noise that is accurate for most GNSS time-series. Numerical results are given for a set of synthetic data and a set of International GNSS Service (IGS) stations, demonstrating a reduction in computation time of a factor of 10–100 compared to the standard MLE method, depending on the length of the time-series and the amount of missing data. Numéro de notice : A2013-218 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0605-0 Date de publication en ligne : 02/12/2012 En ligne : https://doi.org/10.1007/s00190-012-0605-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32356 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013041	SL	Revue	Centre de documentation	Revues en salle	Disponible

High-rate precise point positioning (PPP) to measure seismic wave motions : an experimental comparison of GPS PPP with inertial measurement units / Peiliang Xu in Journal of geodesy, vol 87 n° 4 (April 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 4 (April 2013) . - pp 361 - 372 Titre : High-rate precise point positioning (PPP) to measure seismic wave motions : an experimental comparison of GPS PPP with inertial measurement units Type de document : Article/Communication Auteurs : Peiliang Xu, Auteur ; Chuang Shi, Auteur ; Rongxin Fang, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 361 - 372 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] centrale inertielle [Termes IGN] corrélation croisée normalisée [Termes IGN] onde sismique [Termes IGN] orientation du capteur [Termes IGN] positionnement absolu [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision millimétrique Résumé : (Auteur) High-rate GPS has been widely used to construct displacement waveforms and to invert for source parameters of earthquakes. Almost all works on internal and external evaluation of high-rate GPS accuracy are based on GPS relative positioning. We build an experimental platform to externally evaluate the accuracy of 50-Hz PPP displacement waveforms. Since the shake table allows motion in any of six degrees of freedom, we install an inertial measurement unit (IMU) to measure the attitude of the platform and transform the IMU displacements into the GPS coordinate system. The experimental results have shown that high-rate PPP can produce absolute horizontal displacement waveforms at the accuracy of 2–4 mm and absolute vertical displacement waveforms at the sub-centimeter level of accuracy within a short period of time. The significance of the experiments indicates that high-rate PPP is capable of detecting absolute seismic displacement waveforms at the same high accuracy as GPS relative positioning techniques, but requires no fixed datum station. We have also found a small scaling error of IMU and a small time offset of misalignment between high-rate PPP and IMU displacement waveforms by comparing the amplitudes of and cross-correlating both the displacement waveforms. Numéro de notice : A2013-219 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0606-z Date de publication en ligne : 09/12/2012 En ligne : https://doi.org/10.1007/s00190-012-0606-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32357 [article]

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266-2013041	SL	Revue	Centre de documentation	Revues en salle	Disponible

On the formulation of the alternative hypothesis for geodetic outlier detection / Rüdiger Lehmann in Journal of geodesy, vol 87 n° 4 (April 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 4 (April 2013) . - pp 373 - 386 Titre : On the formulation of the alternative hypothesis for geodetic outlier detection Type de document : Article/Communication Auteurs : Rüdiger Lehmann, Auteur Année de publication : 2013 Article en page(s) : pp 373 - 386 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Statistiques [Termes IGN] algorithme de décalage moyen [Termes IGN] compensation de coordonnées [Termes IGN] erreur géométrique [Termes IGN] méthode de Monte-Carlo [Termes IGN] valeur aberrante [Termes IGN] variable aléatoire [Termes IGN] variance Résumé : (Auteur) The concept of outlier detection by statistical hypothesis testing in geodesy is briefly reviewed. The performance of such tests can only be measured or optimized with respect to a proper alternative hypothesis. Firstly, we discuss the important question whether gross errors should be treated as non-random quantities or as random variables. In the first case, the alternative hypothesis must be based on the common mean shift model, while in the second case, the variance inflation model is appropriate. Secondly, we review possible formulations of alternative hypotheses (inherent, deterministic, slippage, mixture) and discuss their implications. As measures of optimality of an outlier detection, we propose the premium and protection, which are briefly reviewed. Finally, we work out a practical example: the fit of a straight line. It demonstrates the impact of the choice of an alternative hypothesis for outlier detection. Numéro de notice : A2013-220 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0607-y Date de publication en ligne : 21/12/2012 En ligne : https://doi.org/10.1007/s00190-012-0607-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32358 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013041	SL	Revue	Centre de documentation	Revues en salle	Disponible