Centre de documentation
scientifique

Dépouillements

A comparison of recent Earth gravitational models with emphasis on their contribution in refining the gravity and geoid at continental or regional scale / D. Arabelos in Journal of geodesy, vol 84 n° 11 (November 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 11 (November 2010) . - pp 643 - 660 Titre : A comparison of recent Earth gravitational models with emphasis on their contribution in refining the gravity and geoid at continental or regional scale Type de document : Article/Communication Auteurs : D. Arabelos, Auteur ; C.C. Tscherning, Auteur Année de publication : 2010 Article en page(s) : pp 643 - 660 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] champ de pesanteur local [Termes IGN] champ de pesanteur terrestre [Termes IGN] covariance [Termes IGN] données GRACE [Termes IGN] Earth Gravity Model 1996 [Termes IGN] Earth Gravity Model 2008 [Termes IGN] géoïde terrestre Résumé : (Auteur) Since the publication of the Earth gravitational model (EGM) 96 considerable improvements in the observation techniques resulted in the development of new improved models. The improvements are due to the availability of data from dedicated gravity mapping missions (CHAMP, GRACE) and to the use of 5? * 5? terrestrial and altimetry derived gravity anomalies. It is expected that the use of new EGMs will further contribute to the improvement of the resolution and accuracy of the gravity and geoid modeling in continental and regional scale. To prove this numerically, three representative Earth gravitational models are used for the reduction of several kinds of data related to the gravity field in different places of the Earth. The results of the reduction are discussed regarding the corresponding covariance functions which might be used for modeling using the least squares collocation method. The contribution of the EIGEN-GL04C model in most cases is comparable to that of EGM96. However, the big difference is shown in the case of EGM2008, due not only to its quality but obviously to its high degree of expansion. Almost in all cases the variance and the correlation length of the covariance functions of data reduced to this model up to its maximum degree are only a few percentages of corresponding quantities of the same data reduced up to degree 360. Furthermore, the mean value and the standard deviation of the reduced gravity anomalies in extended areas of the Earth such as Australia, Arctic region, Scandinavia or the Canadian plains, vary between -1 and +1 and between 5 and 10 * 10-5 ms-2, respectively, reflecting the homogenization of the gravity field on a regional scale. This is very important in using least squares collocation for regional applications. However, the distance to the first zero-value was in several cases much longer than warranted by the high degree of the expansion. This is attributed to errors of medium wavelengths stemming from the lack of, e.g., high-quality data in some area. Numéro de notice : A2010-476 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0397-z Date de publication en ligne : 15/09/2010 En ligne : https://doi.org/10.1007/s00190-010-0397-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30669 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010111	SL	Revue	Centre de documentation	Revues en salle	Disponible

The celestial mechanics approach: application to data of the GRACE mission / Gerhard Beutler in Journal of geodesy, vol 84 n° 11 (November 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 11 (November 2010) . - pp 661 - 681 Titre : The celestial mechanics approach: application to data of the GRACE mission Type de document : Article/Communication Auteurs : Gerhard Beutler, Auteur ; Adrian Jäggi, Auteur ; L. Mervart, Auteur Année de publication : 2010 Article en page(s) : pp 661 - 681 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] bande K [Termes IGN] données GPS [Termes IGN] données GRACE [Termes IGN] mécanique céleste [Termes IGN] orbitographie Résumé : (Auteur) The celestial mechanics approach (CMA) has its roots in the Bernese GPS software and was extensively used for determining the orbits of high-orbiting satellites. The CMA was extended to determine the orbits of Low Earth Orbiting satellites (LEOs) equipped with GPS receivers and of constellations of LEOs equipped in addition with inter-satellite links. In recent years, the CMA was further developed and used for gravity field determination. The CMA was developed by the Astronomical Institute of the University of Bern (AIUB). The CMA is presented from the theoretical perspective in (Beutler et al. 2010). The key elements of the CMA are illustrated here using data from 50 days of GPS, K-Band, and accelerometer observations gathered by the Gravity Recovery And Climate Experiment (GRACE) mission in 2007. We study in particular the impact of (1) analyzing different observables [Global Positioning System (GPS) observations only, inter-satellite measurements only], (2) analyzing a combination of observations of different types on the level of the normal equation systems (NEQs), (3) using accelerometer data, (4) different orbit parametrizations (short-arc, reduced-dynamic) by imposing different constraints on the stochastic orbit parameters, and (5) using either the inter-satellite ranges or their time derivatives. The so-called GRACE baseline, i.e., the achievable accuracy of the GRACE gravity field for a particular solution strategy, is established for the CMA. Numéro de notice : A2010-477 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0402-6 Date de publication en ligne : 21/08/2010 En ligne : https://doi.org/10.1007/s00190-010-0402-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30670 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010111	SL	Revue	Centre de documentation	Revues en salle	Disponible

Fast GNSS ambiguity resolution as an ill-posed problem / Lard Erik Sjöberg in Journal of geodesy, vol 84 n° 11 (November 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 11 (November 2010) . - pp 699 - 702 Titre : Fast GNSS ambiguity resolution as an ill-posed problem Type de document : Article/Communication Auteurs : Lard Erik Sjöberg, Auteur Année de publication : 2010 Article en page(s) : pp 699 - 702 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] matrice de covariance [Termes IGN] mesurage de phase [Termes IGN] phase GNSS [Termes IGN] positionnement par GNSS [Termes IGN] problème inverse [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) A linear observational equation system for real-time GNSS carrier phase ambiguity resolution (AR) is often severely ill-posed in the case of poor satellite geometry. An ill-posed system may result in unreliable or unsuccessful AR if no care is taken to mitigate this situation. In this paper, the GNSS AR model as an ill-posed problem is solved by regularizing its baseline and ambiguity parameters, respectively, with the threefold contributions: (i) The regularization parameter is reliably determined in context of minimizing mean square error of regularized solution where the covariance matrix of initial values of unknowns is used as an approximate smoothness term instead of the quadratic matrix of the true values of unknowns; (ii) The different models for computing initial values of unknowns are systematically discussed in order to address the potential schemes in real world applications; (iii) The superior performance of the regularized AR are demonstrated through the numerically random simulations as well as the real GPS experiments. The results show that the proposed regularization strategies can effectively mitigate the model’s ill-condition and improve the success AR probability of the observational system with a severely ill-posed problem. Numéro de notice : A2010-478 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0403-5 Date de publication en ligne : 22/08/2010 En ligne : https://doi.org/10.1007/s00190-010-0403-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30671 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010111	SL	Revue	Centre de documentation	Revues en salle	Disponible