Publications de l'équipe Géodésie de l'UMR IPGP
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Semi-parametric segmentation of multiple series using a DP-Lasso strategy / Karine Bertin in Journal of Statistical Computation and Simulation, vol 87 n° 6 (2017)
[article]
Titre : Semi-parametric segmentation of multiple series using a DP-Lasso strategy Type de document : Article/Communication Auteurs : Karine Bertin, Auteur ; Xavier Collilieux , Auteur ; Emilie Lebarbier, Auteur ; Christian Meza, Auteur Année de publication : 2017 Projets : 3-projet - voir note / Article en page(s) : pp 1255 - 1268 Note générale : bibliographie
This work was supported by FONDECYT [grant numbers 1141256 and 1141258]; ANILLO [grant number ACT-1112]; MATH-AmSud [grant number 16-MATH-03]; SIDRE and CONICYT [grant number 870100003].Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie
[Termes IGN] données géodésiques
[Termes IGN] estimation statistique
[Termes IGN] itération
[Termes IGN] programmation dynamique
[Termes IGN] segmentationRésumé : (auteur) We consider a semi-parametric approach to perform the joint segmentation of multiple series sharing a common functional part. We propose an iterative procedure based on Dynamic Programming for the segmentation part and Lasso estimators for the functional part. Our Lasso procedure, based on the dictionary approach, allows us to both estimate smooth functions and functions with local irregularity, which permits more flexibility than previous proposed methods. This yields to a better estimation of the functional part and improvements in the segmentation. The performance of our method is assessed using simulated data and real data from agriculture and geodetic studies. Our estimation procedure results to be a reliable tool to detect changes and to obtain an interpretable estimation of the functional part of the model in terms of known functions. Numéro de notice : A2017-870 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00949655.2016.1260726 Date de publication en ligne : 30/11/2016 En ligne : https://doi.org/10.1080/00949655.2016.1260726 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89907
in Journal of Statistical Computation and Simulation > vol 87 n° 6 (2017) . - pp 1255 - 1268[article]GPS - Zenith Total Delay assimilation in different resolution simulations of a heavy precipitation event over southern France / Alberto Caldas-Álvarez in Advances in Science and Research, vol 14 (2017)
[article]
Titre : GPS - Zenith Total Delay assimilation in different resolution simulations of a heavy precipitation event over southern France Type de document : Article/Communication Auteurs : Alberto Caldas-Álvarez, Auteur ; Samiro Khodayar, Auteur ; Olivier Bock , Auteur Année de publication : 2017 Projets : HyMeX / Richard, Evelyne Conférence : EMS 2016, 16th European Meteorological Society annual meeting 12/09/2016 16/09/2016 Trieste Italie Projets : IODA-Med / Richard, Evelyne, REMEMBER / Drobinski, Philippe Article en page(s) : pp 157 - 162 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] distribution spatiale
[Termes IGN] humidité de l'air
[Termes IGN] précipitation
[Termes IGN] retard troposphérique zénithal
[Termes IGN] teneur intégrée en vapeur d'eauRésumé : (auteur) The aim of this study is to investigate the different pathways of the interaction between an improved atmospheric moisture distribution by Data Assimilation (DA) of Global Positioning System Zenith Total Delays (GPS-ZTD) on the simulation of a selected Heavy Precipitation Event (HPE) across different model horizontal resolutions (7 km, 2.8 km and 500 m). The initiation and evolution of deep moist convection and heavy precipitation taking place on the 24 September 2012, which had a dedicated Intensive Observation Period (IOP6) during the Hydrological cycle in the Mediterranean eXperiment (HyMeX) Special Observation period 1, are analysed. The results show an improvement in the representation of the Integrated Water Vapour (IWV) spatial distribution and temporal evolution when the data assimilation is applied as well as through the refinement of the model grids. However, important discrepancies between the simulated and the observed vertical profiles of humidity still remain after the DA, thus affecting the representation of convection and heavy precipitation. For the presented case study, the model simulations exhibited a wet bias. The assimilation entailed a drying of the low to middle troposphere over the study region during the 6 h prior to the storm initiation for every horizontal resolution. This reduced the instability present at the moment of storm initiation, weakening in return the intensity of convection and the number of cells triggered. The improvement observed in the atmospheric moisture content and distribution was not followed by an improved precipitation representation closer to observations. This highlights the relevance of correctly distributing the assimilated IWV in the vertical direction in the models. Numéro de notice : A2017-862 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/asr-14-157-2017 Date de publication en ligne : 13/06/2017 En ligne : https://doi.org/10.5194/asr-14-157-2017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89849
in Advances in Science and Research > vol 14 (2017) . - pp 157 - 162[article]Documents numériques
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GPS - Zenith Total Delay assimilation ... - pdf éditeurAdobe Acrobat PDF GRACE era variability in the Earth's oblateness: a comparison of estimates from six different sources / Thierry Meyrath in Geophysical journal international, vol 208 n° 2 (February 2017)
[article]
Titre : GRACE era variability in the Earth's oblateness: a comparison of estimates from six different sources Type de document : Article/Communication Auteurs : Thierry Meyrath, Auteur ; Paul Rebischung , Auteur ; Tonie M. van Dam, Auteur Année de publication : 2017 Projets : 1-Pas de projet / Drobinski, Philippe Article en page(s) : pp 1126 - 1138 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] données GRACE
[Termes IGN] données TLS (télémétrie)
[Termes IGN] gravimétrie spatiale
[Termes IGN] longueur du jour
[Termes IGN] potentiel de pesanteur terrestre
[Termes IGN] rotation de la Terre
[Termes IGN] série temporelleRésumé : (auteur) We study fluctuations in the degree-2 zonal spherical harmonic coefficient of the Earth's gravity potential, C20, over the period 2003–2015. This coefficient is related to the Earth's oblateness and studying its temporal variations, ΔC20, can be used to monitor large-scale mass movements between high and low latitude regions. We examine ΔC20 inferred from six different sources, including satellite laser ranging (SLR), GRACE and global geophysical fluids models. We further include estimates that we derive from measured variations in the length-of-day (LOD), from the inversion of global crustal displacements as measured by GPS, as well as from the combination of GRACE and the output of an ocean model as described by Sun et al. We apply a sequence of trend and seasonal moving average filters to the different time-series in order to decompose them into an interannual, a seasonal and an intraseasonal component. We then perform a comparison analysis for each component, and we further estimate the noise level contained in the different series using an extended version of the three-cornered-hat method. For the seasonal component, we generally obtain a very good agreement between the different sources, and except for the LOD-derived series, we find that over 90 per cent of the variance in the seasonal components can be explained by the sum of an annual and semiannual oscillation of constant amplitudes and phases, indicating that the seasonal pattern is stable over the considered time period. High consistency between the different estimates is also observed for the intraseasonal component, except for the solution from GRACE, which is known to be affected by a strong tide-like alias with a period of about 161 d. Estimated interannual components from the different sources are generally in agreement with each other, although estimates from GRACE and LOD present some discrepancies. Slight deviations are further observed for the estimate from the geophysical models, likely to be related to the omission of polar ice and groundwater changes in the model combination we use. On the other hand, these processes do not seem to play an important role at seasonal and shorter timescales, as the sum of modelled atmospheric, oceanic and hydrological effects effectively explains the observed C20 variations at those scales. We generally obtain very good results for the solution from SLR, and we confirm that this well-established technique accurately tracks changes in C20. Good agreement is further observed for the estimate from the GPS inversion, showing that this indirect method is successful in capturing fluctuations in C20 on scales ranging from intra- to interannual. Obtaining accurate estimates from LOD, however, remains a challenging task and more reliable models of atmospheric wind fields are needed in order to obtain high-quality ΔC20, in particular at the seasonal scale. The combination of GRACE data and the output of an ocean model appears to be a promising approach, particularly since corresponding ΔC20 is not affected by tide-like aliases, and generally gives better results than the solution from GRACE, which still seems to be of rather poor quality. Numéro de notice : A2017-863 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggw441 Date de publication en ligne : 24/11/2016 En ligne : https://doi.org/10.1093/gji/ggw441 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89852
in Geophysical journal international > vol 208 n° 2 (February 2017) . - pp 1126 - 1138[article]
Titre : Analysis and results of ITRF2014 Type de document : Rapport Auteurs : Zuheir Altamimi , Auteur ; Paul Rebischung , Auteur ; Laurent Métivier , Auteur ; Xavier Collilieux , Auteur Editeur : Francfort sur le Main : Bundesamt für Kartographie und Geodäsie Année de publication : 2017 Collection : IERS Technical note, ISSN 1019-4568 num. 38 Importance : 54 p. Format : 21 x 30 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] analyse de données
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] International Terrestrial Reference System
[Termes IGN] point de liaison (géodésie)
[Termes IGN] qualité des données
[Termes IGN] réseau géodésique
[Termes IGN] série temporelle
[Termes IGN] station permanenteRésumé : (Auteur) The ITRF2014 is an improved realization of the International Terrestrial Reference System (ITRS) and is demonstrated to be of higher quality than the past ITRF versions. It involves two main innovations dealing with the modeling of station non-linear motions, namely seasonal (annual and semi-annual) signals present in the time series of station positions and post-seismic deformations for 124 sites that were subject to major earthquakes. It is achieved through a two-step procedure: (1) stacking the time series of station positions and Earth Orientation Parameters (EOPs) provided by the four IERS Technique Centers (TC); (2) combining the long-term solutions as obtained in step 1, together with local ties in co-location sites. The two-step procedure makes use of full variance-covariance information provided in SINEX format. The TC solutions incorporated in the ITRF2014 combination are free from any external constraints, thus preserving the actual space geodesy estimates of station positions and EOPs. The ITRF2014 origin is defined in such a way that it has zero translations and translation rates with respect to the mean Earth center of mass, as defined by the SLR station positions time series. Its scale is defined by zero scale factor and zero scale rate with respect to the mean of VLBI and SLR long-term solutions as obtained by stacking their respective time series. The ITRF2014 orientation (at epoch 2010.0) and its rate are aligned to the ITRF2008 using 127 stations of high geodetic quality. The ITRF2014 includes the positions and velocities of 1499 stations located at 975 sites. Figure 1 shows the coverage of these sites, underlying the co-located space geodesy techniques. This technical note describes the main ITRF2014 products: station positions and velocities, the post fit residuals of the least squares adjustment as well as the transformation parameters between ITRF2014 and ITRF2008. The main technical procedure used to generate the ITRF2014, a thorough discussion of its quality as well as most important geodetic and geophysical results were published in Altamimi et al. [2016], appended to this Technical Note. Note de contenu : 1 Summary
2 ITRF2014 input data
2.1 Space geodesy solutions
2.2 Local ties in co-location sites
3 ITRF2014 data analysis
3.1 Combination model
3.2 ITRF2014 frame definition
4 ITRF2014 results
4.1 ITRF2014 origin and scale
4.2 ITRF2014 products
4.3 Transformation parameters between ITRF2014 and ITRF2008
4.4 Consistency between local ties and space geodesy estimates
5 Access to the ITRF2014 files
5.1 ITRF2014 SINEX files
5.2 ITRF2014 other files
5.3 Post-seismic deformationsNuméro de notice : 17489 Affiliation des auteurs : LASTIG LAREG (2012-mi2018) Autre URL associée : http://www.iers.org/TN38 Thématique : POSITIONNEMENT Nature : Rapport d'étude technique nature-HAL : RappRech DOI : sans Date de publication en ligne : 07/04/2017 En ligne : https://www.iers.org/IERS/EN/Publications/TechnicalNotes/tn38.html;jsessionid=2D [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89945 Cyclic asymptotic behaviour of a population reproducing by fission into two equal parts / Etienne Bernard (2017)
Titre : Cyclic asymptotic behaviour of a population reproducing by fission into two equal parts Type de document : Article/Communication Auteurs : Etienne Bernard , Auteur ; Marie Doumic, Auteur ; Pierre Gabriel, Auteur Mention d'édition : v3 Editeur : Ithaca [New York - Etats-Unis] : ArXiv - Université Cornell Année de publication : 2017 Projets : KIBORD / Drobinski, Philippe Format : 21 Langues : Anglais (eng) Résumé : (auteur) We study the asymptotic behaviour of the following linear growth-fragmentation equation xxxxxxx
and prove that under fairly general assumptions on the division rate B(x),its solution converges towards an oscillatory function,explicitely given by the projection of the initial state on the space generated by the countable set of the dominant eigenvectors of the operator.Despite the lack of hypo-coercivity of the operator, the proof relies on a general relative entropy argument in a convenient weighted L2 space, where well-posedness is obtained via semigroup analysis. We also propose a non-dissipative numerical scheme, able to capture the oscillations.Numéro de notice : P2017-001 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : MATHEMATIQUE Nature : Preprint nature-HAL : Préprint DOI : 10.48550/arXiv.1609.03846 Date de publication en ligne : 02/11/2017 En ligne : https://doi.org/10.48550/arXiv.1609.03846 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91916 Voir aussiDocuments numériques
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