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Velocity field and crustal deformation of broader Athens plain (Greece) from a dense geodetic network / Michael Foumelis in Journal of applied geodesy, Vol 13 n° 4 (October 2019)  

Public [article]  inJournal of applied geodesy > Vol 13 n° 4 (October 2019) . - pp 305 – 316 Titre : Velocity field and crustal deformation of broader Athens plain (Greece) from a dense geodetic network Type de document : Article/Communication Auteurs : Michael Foumelis, Auteur Année de publication : 2019 Article en page(s) : pp 305 – 316 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Athènes [Termes IGN] calcul tensoriel [Termes IGN] champ de vitesse [Termes IGN] déformation de la croute terrestre [Termes IGN] extensométrie [Termes IGN] géodynamique [Termes IGN] positionnement par GNSS [Termes IGN] réseau géodésique dense [Termes IGN] tectonique Résumé : (auteur) The broader area of Athens, a region exhibiting relatively low crustal deformation, was stroke in 1999 by a catastrophic earthquake posing serious questions regarding strain accumulation in slow deforming regions located within active geodynamic regimes. In the present study, the establishment of a dense geodetic network, primarily designed to monitor local tectonic movements is reported. A comprehensive GNSS velocity field, over the period 2005–2008, as well as calculated geodetic strain rates is presented. It is shown that a single strain tensor is insufficient to express the heterogeneity of the local geodetic field. Local variability of strain is successfully depicted, indicating the western part of Athens as the area of higher strain accumulation. Maximum dilatation rates occur along a NNE-SSW direction between Parnitha Mt. and Thriasio basin. The observed dilatation can be associated to WNW-ESE trending active fault zones, which appear to abruptly terminate towards East along a major NNE-SSW Miocene tectonic boundary. These findings are consistent to the stress field responsible for the Athens 1999 earthquake, also in agreement with geological and tectonic observations. Finally, the implications of the observed motion field on the understanding of the kinematics and dynamics of the region as well as the role of inherited inactive tectonic structures are discussed. Numéro de notice : A2019-541 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2019-0012 Date de publication en ligne : 04/07/2019 En ligne : https://doi.org/10.1515/jag-2019-0012 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94180 [article]

Modeling tropospheric wet delays with dense and sparse network configurations for PPP-RTK / Paulo S. de Oliveira in GPS solutions, vol 21 n° 1 (January 2017)  

Public [article]  inGPS solutions > vol 21 n° 1 (January 2017) . - pp 237 - 250 Titre : Modeling tropospheric wet delays with dense and sparse network configurations for PPP-RTK Type de document : Article/Communication Auteurs : Paulo S. de Oliveira, Auteur ; Laurent Morel, Auteur ; François Fund, Auteur ; Romain Legros, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 237 - 250 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] France d'outre-mer [Termes IGN] orbite précise [Termes IGN] Orphéon [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GLONASS [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur bifréquence [Termes IGN] réseau géodésique clairsemé [Termes IGN] réseau géodésique dense [Termes IGN] retard troposphérique [Termes IGN] retard troposphérique zénithal Résumé : (Auteur) Precise Point Positioning (PPP) is a well-known technique of positioning by Global Navigation Satellite Systems (GNSS) that provides accurate solutions. With the availability of real-time precise orbit and clock products provided by the International GNSS Service (IGS) and by individual analysis centers such as Centre National d’Etudes Spatiales through the IGS Real-Time Project, PPP in real time is achievable. With such orbit and clock products and using dual-frequency receivers, first-order ionospheric effects can be eliminated by the ionospheric-free combination. Concerning the tropospheric delays, the Zenith Hydrostatic Delays can be quite well modeled, although the Zenith Wet Delays (ZWDs) have to be estimated because they cannot be mitigated by, for instance, observable combinations. However, adding ZWD estimates in PPP processing increases the time to achieve accurate positions. In order to reduce this convergence time, we (1) model the behavior of troposphere over France using ZWD estimates at Orphéon GNSS reference network stations and (2) send the modeling parameters to the GNSS users to be introduced as a priori ZWDs, with an appropriate uncertainty. At the user level, float PPP-RTK is achieved; that is, GNSS data are performed in kinematic mode and ambiguities are kept float. The quality of the modeling is assessed by comparison with tropospheric products published by Institut National de l’Information Géographique et Forestière. Finally, the improvements in terms of required time to achieve 10-cm accuracy for the rover position (simulated float PPP-RTK) are quantified and discussed. Results for 68 % quantiles of absolute errors convergence show that gains for GPS-only positioning with ZWDs derived from the assessed tropospheric modeling are about: 1 % (East), 20 % (North), and 5 % (Up). Since ZWD estimation is correlated with satellite geometry, we also investigated the positioning when processing GPS + GLONASS data, which increases significantly the number of available satellites. The improvements achieved by adding tropospheric corrections in this case are about: 2 % (East), 5 % (North), and 13 % (Up). Finally, a reduction in the number of reference stations by using a sparser network configuration to perform the tropospheric modeling does not degrade the generated tropospheric corrections, and similar performances are achieved. Numéro de notice : A2017-017 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0518-0 En ligne : http://dx.doi.org/10.1007/s10291-016-0518-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83948 [article]