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Relativistic geodesy, ch. 2. Chronometric geodesy: Methods and applications / Pacôme Delva (2019)  

Public Titre de série : Relativistic geodesy, ch. 2 Titre : Chronometric geodesy: Methods and applications Type de document : Chapitre/Contribution Auteurs : Pacôme Delva, Auteur ; Heiner Denker, Auteur ; Guillaume Lion , Auteur Editeur : Springer International Publishing Année de publication : 2019 Collection : Fundamental Theories of Physics num. 196 Projets : ITOC / , AdOC / , FIRST-TF / Importance : pp 25 - 85 Note générale : bibliographie This research was supported by the European Metrology Research Programme (EMRP) within the Joint Research Project “International Timescales with Optical Clocks” (SIB55 ITOC), as well as the Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Centre 1128 “Relativistic Geodesy and Gravimetry with Quantum Sensors (geo-Q)”, project C04. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. We gratefully acknowledge financial support from Labex FIRST-TF and ERC AdOC (Grant No. 617553). Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] chronométrie [Termes IGN] décalage d'horloge [Termes IGN] échelle de temps [Termes IGN] horloge atomique Résumé : (auteur) The theory of general relativity was born more than one hundred years ago, and since the beginning has striking prediction success. The gravitational redshift effect discovered by Einstein must be taken into account when comparing the frequencies of distant clocks. However, instead of using our knowledge of the Earth’s gravitational field to predict frequency shifts between distant clocks, one can revert the problem and ask if the measurement of frequency shifts between distant clocks can improve our knowledge of the gravitational field. This is known as chronometric geodesy. Since the beginning of the atomic time era in 1955, the accuracy and stability of atomic clocks were constantly ameliorated, with around one order of magnitude gained every ten years. Now that the atomic clock accuracy reaches the low 10−18 in fractional frequency, and can be compared to this level over continental distances with optical fibres, the accuracy of chronometric geodesy reaches the cm level and begins to be competitive with classical geodetic techniques such as geometric levelling and GNSS/geoid levelling. Moreover, the building of global timescales requires now to take into account these effects to the best possible accuracy. In this chapter we explain how atomic clock comparisons and the building of timescales can benefit from the latest developments in physical geodesy for the modelization and realization of the geoid, as well as how classical geodesy could benefit from this new type of observable, which are clock comparisons that are directly linked to gravity potential differences. Numéro de notice : H2019-006 Affiliation des auteurs : Géodésie+Ext (mi2018-2019) Thématique : POSITIONNEMENT Nature : Chapître / contribution nature-HAL : ChOuvrScient DOI : 10.1007/978-3-030-11500-5_2 Date de publication en ligne : 10/02/2019 En ligne : https://doi.org/10.1007/978-3-030-11500-5_2 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95546

Determination of a high spatial resolution geopotential model using atomic clock comparisons / Guillaume Lion in Journal of geodesy, vol 91 n° 6 (June 2017)    

Public [article]  inJournal of geodesy > vol 91 n° 6 (June 2017) . - pp 597 - 611 Titre : Determination of a high spatial resolution geopotential model using atomic clock comparisons Type de document : Article/Communication Auteurs : Guillaume Lion , Auteur ; Isabelle Panet , Auteur ; Peter Wolf, Auteur ; C. Guerlin, Auteur ; Sébastien Bize, Auteur ; Pacôme Delva, Auteur Année de publication : 2017 Projets : FIRST-TF / , AdOC / , ITOC / Article en page(s) : pp 597 - 611 Note générale : Bibliographie We gratefully acknowledge financial support from Labex FIRST-TF, ERC AdOC(Grant No. 617553 and EMRP ITOC (EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union). Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Alpes (France) [Termes IGN] champ de pesanteur local [Termes IGN] collocation par moindres carrés [Termes IGN] covariance [Termes IGN] erreur systématique [Termes IGN] horloge atomique [Termes IGN] horlogerie [Termes IGN] levé gravimétrique [Termes IGN] Massif central (France) [Termes IGN] modèle de géopotentiel local [Termes IGN] qualité des données Résumé : (Auteur) Recent technological advances in optical atomic clocks are opening new perspectives for the direct determination of geopotential differences between any two points at a centimeter-level accuracy in geoid height. However, so far detailed quantitative estimates of the possible improvement in geoid determination when adding such clock measurements to existing data are lacking. We present a first step in that direction with the aim and hope of triggering further work and efforts in this emerging field of chronometric geodesy and geophysics. We specifically focus on evaluating the contribution of this new kind of direct measurements in determining the geopotential at high spatial resolution (≈10 km). We studied two test areas, both located in France and corresponding to a middle (Massif Central) and high (Alps) mountainous terrain. These regions are interesting because the gravitational field strength varies greatly from place to place at high spatial resolution due to the complex topography. Our method consists in first generating a synthetic high-resolution geopotential map, then drawing synthetic measurement data (gravimetry and clock data) from it, and finally reconstructing the geopotential map from that data using least squares collocation. The quality of the reconstructed map is then assessed by comparing it to the original one used to generate the data. We show that adding only a few clock data points (less than 1% of the gravimetry data) reduces the bias significantly and improves the standard deviation by a factor 3. The effect of the data coverage and data quality on the results is investigated, and the trade-off between the measurement noise level and the number of data points is discussed. Numéro de notice : A2017-286 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0986-6 Date de publication en ligne : 11/01/2017 En ligne : http://dx.doi.org/10.1007/s00190-016-0986-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85319 [article]

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