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Fiducial reference systems for time and coordinates in satellite altimetry / Stelios Mertikas in Advances in space research, vol 68 n° 2 (15 July 2021)  

Public [article]  inAdvances in space research > vol 68 n° 2 (15 July 2021) . - pp 1140 - 1160 Titre : Fiducial reference systems for time and coordinates in satellite altimetry Type de document : Article/Communication Auteurs : Stelios Mertikas, Auteur ; Craig Donlon, Auteur ; Demetrios Matsakis, Auteur ; Constantin Mavrocordatos, Auteur ; Zuheir Altamimi , Auteur ; Costas Kokolakis, Auteur ; Achilles Tripolitsiotis, Auteur Année de publication : 2021 Projets : 3-projet - voir note / Article en page(s) : pp 1140 - 1160 Note générale : bibliographie Part of this work has been produced with the financial assistance of the European Union and the European Space Agency under the project FRM4S6 (Fiducial Reference Systems For Sentinel-6, No. 4000129892/20/NL/FF/ab) Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] altimétrie satellitaire par radar [Termes IGN] coordonnées cartésiennes géocentriques [Termes IGN] système de référence altimétrique Résumé : (auteur) Time is the fundamental measurement in satellite altimetry and the key parameter in building and keeping up a long-term, consistent, and reliable record for monitoring changes in sea level. Over the years, different time scales, although interconnected, have been used in altimetry and also in satellite positioning. This sometimes leads to inexplicit descriptions and ambiguous use of time and orbit coordinates as well as of their transformations between various reference and measuring systems. Altimetry satellites, like Sentinel-3, CryoSat-2, Jason-3, HY-2A/-2B, IceSat-2, etc., observe and practically realize ranges by measuring time differences between the transmission and reception of an electromagnetic wave (either radar or laser at present). Similar principles apply for global navigation satellite systems and for their terrestrial reference systems upon which altimetry is linked and tied together. Yet, the “meter” of any terrestrial reference systems is also defined by time. This work seeks to establish a standard reference system for “time” and “coordinates” in an effort to reach uniform and absolute standardization for satellite altimetry. It describes various errors generated from differences, discontinuities and interactions in time, frequency, range, time tagging, and reference coordinate frames. A new approach, called “fiducial reference measurements for altimetry”, is here given to examine ways to connect errors with metrology standards in order to improve the estimation of uncertainty budgets in ocean and water level observation by altimetry. Finally, the geocentric inertial reference system and the international atomic time are proposed in this paper for satellite altimetry observations and products. Numéro de notice : A2021-601 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2020.05.014 En ligne : https://doi.org/10.1016/j.asr.2020.05.014 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98240 [article]

DORIS and GPS monitoring of the Gavdos calibration site in Crete / Pascal Willis in Advances in space research, vol 51 n° 8 (April 2013)  

Public [article]  inAdvances in space research > vol 51 n° 8 (April 2013) . - pp 1438 - 1447 Titre : DORIS and GPS monitoring of the Gavdos calibration site in Crete Type de document : Article/Communication Auteurs : Pascal Willis , Auteur ; Stelios Mertikas, Auteur ; Donald F. Argus, Auteur ; Olivier Bock , Auteur Année de publication : 2013 Projets : Gavdos / Article en page(s) : pp 1438 - 1447 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] analyse diachronique [Termes IGN] correction troposphérique [Termes IGN] Crète (île) [Termes IGN] étalonnage des données [Termes IGN] GAMIT [Termes IGN] International Terrestrial Reference Frame [Termes IGN] modèle météorologique [Termes IGN] positionnement par DORIS [Termes IGN] positionnement par GPS [Termes IGN] retard troposphérique zénithal [Termes IGN] série temporelle Résumé : (auteur) Due to its specific geographical location as well as its geodetic equipment (DORIS, GNSS, microwave transponder and tide gauges), the Gavdos station in Crete, Greece is one of the very few sites around the world used for satellite altimetry calibration. To investigate the quality of the Gavdos geodetic coordinates and velocities, we analyzed and compared here DORIS and GPS-derived results obtained during several years of observations. The DORIS solution is the latest ignwd11 solution at IGN, expressed in ITRF2008, while the GPS solution was obtained using the GAMIT software package. Current results show that 1–2 mm/yr agreement can be obtained for 3-D velocity, showing a good agreement with current geophysical models. In particular, the agreement obtained for the vertical velocity is around 0.3–0.4 mm/yr, depending on the terrestrial reference frame. As a by-product of these geodetic GPS and DORIS results, Zenith Tropospheric Delays (ZTDs) estimations were also compared in 2010 between these two techniques, and compared to ECMWF values, showing a 6.6 mm agreement in dispersion without any significant difference between GPS and DORIS (with a 97.6% correlation), but with a 13–14 mm agreement in dispersion when comparing to ECMWF model (with only about 90% correlation for both techniques). These tropospheric delay estimations could also provide an external calibration of the tropospheric correction used for the geophysical data of satellite altimetry missions. Numéro de notice : A2013-798 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2012.08.006 En ligne : http://dx.doi.org/10.1016/j.asr.2012.08.006 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80125 [article]

Gravity, Geoid and Earth Observation, IAG Commission 2 Gravity Field, Chania, Crete, Greece, 23-27 June 2008 / Stelios Mertikas (2010)  

Public Titre : Gravity, Geoid and Earth Observation, IAG Commission 2 Gravity Field, Chania, Crete, Greece, 23-27 June 2008 Type de document : Actes de congrès Auteurs : Stelios Mertikas, Éditeur scientifique Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2010 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 135 Conférence : IAG 2008 Commission 2, Gravity, Geoid and Earth Observation GGEO 23/06/2008 27/06/2008 Chania Crète - Grèce Proceedings Springer ISBN/ISSN/EAN : 978-3-642-10633-0 Langues : Anglais (eng) Numéro de notice : 17531 Affiliation des auteurs : non IGN Nature : Actes DOI : 10.1007/978-3-642-10634-7 En ligne : https://doi.org/10.1007/978-3-642-10634-7 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90742

Contient

• Assessment of a numerical method for computing the spherical harmonic coefficients of the gravitational potential of a constant density polyhedron / Olivier Jamet (2010)  
• Quasi-Geoid of New Caledonia: Computation Results and Analysis / Pierre Valty (2010)