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Titre : The choice of reference system in ITRF formulation Type de document : Article/Communication Auteurs : Zuheir Altamimi , Auteur ; Athanasios Dermanis, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2012 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 137 Conférence : IAG 2009, 7th Hotine-Marussi Symposium on Mathematical Geodesy 06/06/2009 10/06/2009 Rome Italie Proceedings Springer Importance : pp 329 - 334 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] barycentre
[Termes IGN] coordonnées cartésiennes géocentriques
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] moment cinétique
[Termes IGN] système de référence géodésique
[Termes IGN] vitesseRésumé : (auteur) The problem of choosing an optimal reference system for the International Terrestrial Reference Frame (ITRF) is studied for both the rigorous solution which is a simultaneous stacking (removal of the reference system at each data epoch and implementation of a linear in time coordinate model) for all techniques, as well as for the usual numerically convenient separation into a set of individual stackings one for each technique and a final combination step for the derived initial coordinates and velocities. Two approaches are followed, an algebraic and a kinematic one. The algebraic approach implements the inner constraints, which minimize the sum of squares of the unknown parameters, as well as partial inner constraints, which minimize the sum of squares of a subset of the unknown parameters. In the kinematical approach the optimal minimal constraints are derived by requiring the minimization of the apparent coordinate variations: (a) with respect to the origin by imposing constant coordinates for the network barycenter, (b) with respect to orientation by imposing zero relative angular momentum for the network points conceived as mass points with equal mass and (c) with respect to the scale by imposing constant mean quadratic size (involving the distances of stations from their barycenter). Numéro de notice : C2009-036 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-22078-4_49 Date de publication en ligne : 18/10/2011 En ligne : https://doi.org/10.1007/978-3-642-22078-4_49 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91643 Evidence for a slow subsidence of the Tahiti Island from GPS, DORIS, and combined satellite altimetry and tide gauge sea level records / Abdelali Fadil in Comptes rendus : Géoscience, vol 343 n° 5 (May 2011)
[article]
Titre : Evidence for a slow subsidence of the Tahiti Island from GPS, DORIS, and combined satellite altimetry and tide gauge sea level records Titre original : Indications d’une subsidence lente de l’île de Tahiti par analyse de données de positionnement GPS et DORIS, ainsi que par combinaison de données de suivi du niveau de la mer, d’altimétrie et de marégraphie Type de document : Article/Communication Auteurs : Abdelali Fadil, Auteur ; Lydie Sichoix, Auteur ; Jean-Pierre Barriot, Auteur ; Pascal Ortéga, Auteur ; Pascal Willis , Auteur Année de publication : 2011 Article en page(s) : pp 331 - 341 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] coordonnées GPS
[Termes IGN] déformation verticale de la croute terrestre
[Termes IGN] données altimétriques
[Termes IGN] données DORIS
[Termes IGN] données marégraphiques
[Termes IGN] montée du niveau de la mer
[Termes IGN] rebond post-glaciaire
[Termes IGN] récif corallien
[Termes IGN] subsidence
[Termes IGN] Tahiti
[Termes IGN] vitesseRésumé : (auteur) Monitoring vertical land motion is of crucial interest in observations of long-term sea level change and its reconstruction, but is among of the most, yet highly challenging, tasks of space geodesy. The aim of the paper is to compare the vertical velocity estimates of Tahiti Island obtained from five independent geophysical measurements, namely a decade of GPS and DORIS data, 17 years sea level difference (altimeter minus tide gauge (TG)) time series, ICE-5G (VM2 L90) Post-Glacial Rebound (PGR) model predictions, and coral reef stratigraphy. Except for the Glacial Isostatic Adjustment (GIA also known as PGR) model, all the techniques are in a good agreement and reveal a very slow subsidence of the Tahiti Island averaged at −0.5 mm/yr which is barely significant. Nevertheless, despite of that vertical motion, Tahiti remains an ideal location for the calibration of satellite altimeter measurements. Numéro de notice : A2011-602 Affiliation des auteurs : IGN+Ext (1940-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : 10.1016/j.crte.2011.02.002 Date de publication en ligne : 02/05/2011 En ligne : https://doi.org/10.1016/j.crte.2011.02.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91676
in Comptes rendus : Géoscience > vol 343 n° 5 (May 2011) . - pp 331 - 341[article]Analysis of long-term GPS observations in Greece (1993-2009) and geodynamic implications for the Eastern Mediterranean / Michael D. Müller (2011)
Titre : Analysis of long-term GPS observations in Greece (1993-2009) and geodynamic implications for the Eastern Mediterranean Type de document : Rapport Auteurs : Michael D. Müller, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2011 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 82 Importance : 186 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-28-4 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Athènes
[Termes IGN] champ de vitesse
[Termes IGN] collocation par moindres carrés
[Termes IGN] Egée, mer
[Termes IGN] Grèce
[Termes IGN] méthode des éléments finis
[Termes IGN] Péloponnèse
[Termes IGN] séisme
[Termes IGN] vitesseIndex. décimale : 30.82 Applications géophysiques de géodésie spatiale Résumé : (Auteur) The Global Positioning System (GPS) is used to determine rates of crustal motion in the Hellenic plate boundary zone since the late eighties. The zone comprises Greece and its adjacent regions. It is characterized by the interaction of the Eurasian, Anatolian and Nubian plates moving relative to each other. Tectonic processes associated with this motion cause the highest seismic activity of Europe. Nine earthquakes with magnitude six or higher occurred within this region in the period 2006 to 2011. International efforts are being made to achieve a better understanding of the origin and characteristics of ongoing seismotectonic processes. The ETH Zurich has taken active part in these efforts. Results achieved so far provide valuable boundary conditions for geodynamic modeling. In close collaboration with other institutes an extensive GPS network has been established and periodically remeasured. The network consists of campaign-type and continuous GPS sites. The corresponding data record has been significantly extended in the course of the thesis. A 16 year record of GPS data (19932009) is available now for Greece. In its first part the thesis deals with the evaluation of the data record. The strategy of GPS analysis was enhanced compared to proceeding projects by applying recent GPS processing models and improving postprocessing procedures. The concept of including data of numerous IGS and EUREF sites located in Europe, North Africa and the Middle East was continued. This allowed for a precise alignment of the GPS network to a global reference frame (ITRF2005), the reduction of processing induced systematic signals and the determination of a pole of rotation for the Eurasian plate.
An improved kinematic field was derived which was analyzed in terms of slowly deforming regions by using a block model. The modeling provides several insights. For instance, northwestern Greece rotates clockwise (cw) and the region south of the North Aegean trough (NAT) rotates counterclockwise (ccw) relative to Eurasia. Both areas form blocks with small internal deformation. Moreover, they describe the western termination of the North Aegean trough. A large part of ongoing deformation is located in confined regions.
The GPS derived deformation field provides information about ongoing tectonic processes. These include N-S extension between Northern Greece and the Gulf of Corinth and dextral shear strain in the North Aegean sea as well as along the Kefalonia fault zone in the Ionian sea. New results concerning ongoing deformation processes were achieved in the Southeast Aegean sea and in Northern Greece. Pronounced N-S extension (100 nstrain/yr) was determined across the Mygdonian graben. NNW-SSE extension amounting to 150 nstrain/yr was found between the islands of Kalymnos and Tilos in the SE Aegean sea.
The NAT and the Kefalonia fault zone are among the most pronounced transform faults in the Hellenic plate boundary zone. Rates of closely located GPS sites were used for the estimation of the slip rates and locking depths of the structures. Four profiles across the NAT show a decrease of slip rates from the Ganos fault (23 mm/yr) towards the southwestern edge of the Sporades basin (<5 mm/yr). The geodetic results provide further evidence that the NAT forms the westward continuation of the North Anatolian fault zone commencing at the Saros basin. The decrease of slip rates west of the Chalkidiki peninsula is related to a different orientation of the NAT and to NNE-SSW extension in the Sporades basin. Finite element models were used to relate GPS rates to basic geodynamic models. The first model I focused at the analysis of the subduction rate near the central Hellenic trench. The results point to a largely uncoupled interface between the Nubian and Aegean plates. The second model quantifies the slip rates along the three major NE-SW to ENE-WSW trending transform faults in the North Aegean sea. Rates amounting to 21 mm/yr were derived for the NAT, 10 mm/yr for the Skyros- Edremit fault and 4 mm/yr for the Psara-Lesvos fault. Moreover, the model reveals additional deformation zones such as NNE-SSW extension in the Sporades basin. The derived GPS rates and the conducted analyses improve the current understanding of seismotectonic processes in Greece. The investigations also highlight remaining problems and bring forward new ideas which will ultimately be valuable for further analysis and assessment of natural hazard in Greece.Note de contenu : 1 Introduction
1.1 State of research
1.2 Goals
2 Geologic setting
2.1 Evolution of the central and eastern Mediterranean
2.2 Tectonic framework of Greece
3 GPS data evaluation
3.1 Description of relevant GPS networks
3.1.1 Campaign-type GPS network in Greece and southern Bulgaria
3.1.2 Continuous GPS networks in Greece
3.1.3 IGS and EUREF sites
3.2 Strategy of GPS data processing
3.3 Definition of the geodetic datum
3.4 Velocity estimation of CGPS sites
3.4.1 Introduction
3.4.2 Discontinuities in position time series
3.4.3 Removing outliers
3.4.4 Exclusion periods
3.4.5 Estimation of velocities and offsets
3.4.6 Reduction of apparent scale changes of the processed GPS network
3.4.7 Scaling of formal errors of velocities
3.5 Velocity estimation of campaign-type GPS sites
3.6 Factors affecting the velocity estimates
3.6.1 Tracking performance of GPS sites
3.6.2 Used orbits and earth orientation parameters
3.6.3 Campaign-type data of the years 1993 and 1994
3.7 Concluding remarks
4 Kinematic field in Greece (19932009)
4.1 Introduction
4.2 Euler vector and estimation of a pole of rotation for Eurasia (ITRF2005)
4.3 Kinematic block model for Greece
4.4 Kinematic field and modeling in the North Aegean domain
4.4.1 Kinematic field
4.4.2 Slip rates and locking depths along the North Aegean trough
4.5 Kinematics along the Hellenic trench system
4.5.1 Ionian islands, Western Greece and NW Peloponnesos
4.5.2 Southern Peloponnesos and South Aegean sea
4.6 Vertical motion in Greece
4.7 Concluding remarks
5 Strain rates derived by using the method of collocation
5.1 Least-squares collocation
5.2 Velocity and strain rate fields calculation implemented in the program 'strain'
5.3 Strain rates and differential rotations in Greece
5.4 Concluding remarks
6 Seismic signals in GPS time series
6.1 Introduction
6.2 Estimation of earthquake displacements
6.3 Analytical surface dislocation model
6.4 Earthquakes in the Aegean domain
6.4.1 1999 Ms 5.9 Athens earthquake
6.4.2 2001 Mw 6.4 Skyros earthquake
6.4.3 2008 Mw 6.4 Rhodes earthquake
6.5 Earthquakes in the Ionian sea
6.5.1 1997 Mw 6.6 Strofades earthquake
6.5.2 2003 Mw 6.2 Lefkada earthquake
6.5.3 2006 Zakynthos earthquake series
6.5.4 2008 Mw 6.4 NW Peloponnesos earthquake
6.5.5 Comparison of seismicity and interseismic strain rates
6.6 Concluding remarks
7 Finite element models
7.1 Finite element method
7.1.1 Basic theory
7.1.2 Displacement-based finite element analysis
7.2 Physical properties of a model lithosphere
7.2.1 Introductory notes
7.2.2 Elasticity
7.2.3 Brittle failure
7.2.4 Ductile deformation
7.2.5 Temperature in the continental lithosphere
7.3 Interaction between the overriding and the subducting plate at the central Hellenic trench
7.3.1 Geodetic constraints
7.3.2 Developed finite element model
7.4 3D finite element model of the North Aegean sea
7.4.1 Introduction
7.4.2 Model set up
7.4.3 Results
7.5 Concluding remarks
8 ConclusionsNuméro de notice : 14311 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport de recherche En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-82.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62654 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 14311-01 30.82 Livre Centre de documentation Géodésie Disponible Correlated errors in GPS position time series: Implications for velocity estimates / Alvaro Santamaria Gomez in Journal of geophysical research : Solid Earth, Vol 116 n° B1 (January 2011)
[article]
Titre : Correlated errors in GPS position time series: Implications for velocity estimates Type de document : Article/Communication Auteurs : Alvaro Santamaria Gomez, Auteur ; Marie-Noëlle Bouin , Auteur ; Xavier Collilieux , Auteur ; Guy Wöppelmann , Auteur Année de publication : 2011 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] bruit (théorie du signal)
[Termes IGN] bruit blanc
[Termes IGN] coordonnées GPS
[Termes IGN] erreur instrumentale
[Termes IGN] incertitude de position
[Termes IGN] modèle de Gauss-Markov
[Termes IGN] qualité des données
[Termes IGN] série temporelle
[Termes IGN] vitesse
[Vedettes matières IGN] Traitement de données GNSSRésumé : (auteur) This study focuses on the effects of time correlation in weekly GPS position time series on velocity estimates. Time series 2.5 to 13 years long from a homogeneously reprocessed solution of 275 globally distributed stations are analyzed in terms of noise content and velocity uncertainty assessment. Several noise models were tested, including power law and Gauss‐Markov processes. The best noise model describing our global data set was a combination of variable white noise and power law noise models with mean amplitudes of ∼2 mm and ∼6 mm, respectively, for the sites considered. This noise model provided a mean vertical velocity uncertainty of ∼0.3 mm/yr, 4–5 times larger than the uncorrelated data assumption. We demonstrated that correlated noise content with homogeneously reprocessed data is dependent on time series length and, especially, on data time period. Time series of 2–3 years of the oldest data contain noise amplitude similar to that found for time series of 12 years. The data time period should be taken into account when estimating correlated noise content, when comparing different noise estimations, or when applying an external noise estimation to assess velocity uncertainty. We showed that the data period dependency cannot be explained by the increasing tracking network or the ambiguity fixation rate but is probably related to the amount and quality of recorded data. Numéro de notice : A2011-607 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2010JB007701 Date de publication en ligne : 20/01/2011 En ligne : https://doi.org/10.1029/2010JB007701 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91703
in Journal of geophysical research : Solid Earth > Vol 116 n° B1 (January 2011)[article]Estimation of avalanche front velocities from high speed terrestrial photogrammetry / A. Soruco (2011)
Titre : Estimation of avalanche front velocities from high speed terrestrial photogrammetry Type de document : Article/Communication Auteurs : A. Soruco, Auteur ; Emmanuel Thibert, Auteur ; C. Vincent, Auteur ; Richard Blanc, Auteur ; Raphaële Heno , Auteur Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2011 Conférence : EGU 2011, G 6.1 symposium Geodetic and geodynamic programmes of the central Europe 03/04/2011 08/04/2011 Vienne Autriche programme Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique
[Termes IGN] avalanche
[Termes IGN] modèle numérique de surface
[Termes IGN] séquence d'images
[Termes IGN] vitesseRésumé : (auteur) Avalanche flow models are important tools for avalanche risk mitigation. Artificial avalanche release can provide data for validation of flow models as for example the run-out distance reached by the avalanche. Here we attempt to measure in time the position and velocity of the front of the avalanche in order to provide dynamic data for model calibration. Experiments have been carried out on the full-scale avalanche experimental site at Lautaret pass (French Alps). High speed terrestrial photogrammetry is used to obtain Digital Elevation Models (DEM) during an avalanche release. Recent advances in digital commercial cameras allow acquiring up to 4 frames per second with 10-20 Mpixels of resolution. The principal point position, the focal length and the lens distortion are obtained from calibration, indicating negligible pincushion distortion but significant lens decentration. The camera calibration parameters enable to triangulate two stereo-pairs on ground control points within 6 cm of orientation residuals. A specific DEM generated for comparison with a laser scan DEM reveals a ± 11 cm of random error but no systematic discrepancy. Finally, avalanche front positions and velocities are calculated from a 30 s sequence of stereo pairs acquired during an artificial release with 2 cameras synchronized with digital wireless radio transceivers. Numéro de notice : C2011-044 Affiliation des auteurs : ENSG+Ext (1941-2011) Thématique : IMAGERIE Nature : Communication nature-HAL : ComSansActesPubliés-Unpublished DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96382 Constrained free space diagrams: a tool for trajectory analysis / Kevin Buchin in International journal of geographical information science IJGIS, vol 24 n°7-8 (july 2010)PermalinkEfficient evaluation of continuous spatio-temporal queries on moving objects whith uncertain velocity / Y. Huang in Geoinformatica, vol 14 n° 2 (April 2010)PermalinkReal-time adjustment underwater positioning system for submarines / W. Cheng in Marine geodesy, vol 33 n° 2-3 (April - September 2010)PermalinkThe effects of forest structure on the risk of wind damage at a landscape level in a boreal forest ecosystem / Hongcheng Zeng in Annals of Forest Science, vol 67 n° 1 (January-February 2010)PermalinkValidation and comparison of advanced differential interferometry techniques: Murcia metropolitan area case study / G. Herrera in ISPRS Journal of photogrammetry and remote sensing, vol 64 n° 5 (September - October 2009)PermalinkContinuous K-nearest neighbor query for moving objects with uncertain velocity / Y. Huang in Geoinformatica, vol 13 n° 1 (March 2009)PermalinkSea-surface polarization ratio from Envisat ASAR AP Data / H. Jonhsen in IEEE Transactions on geoscience and remote sensing, vol 46 n° 11 Tome 1 (November 2008)PermalinkTectonique des plaques, séismes et GPS / Christophe Vigny in Géomatique expert, n° 65 (01/11/2008)PermalinkA wavelet based technique for sea wind extraction from SAR images / S. Zecchetto in IEEE Transactions on geoscience and remote sensing, vol 46 n° 10 Tome 1 (October 2008)PermalinkMapping of river surface currents with GNSS / J. Bancroft in Geomatica, vol 62 n° 3 (September 2008)Permalink