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Bayesian-deep-learning estimation of earthquake location from single-station observations / S. Mostafa Mousavi in IEEE Transactions on geoscience and remote sensing, vol 58 n° 11 (November 2020)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 58 n° 11 (November 2020) . - pp 8211 - 8224 Titre : Bayesian-deep-learning estimation of earthquake location from single-station observations Type de document : Article/Communication Auteurs : S. Mostafa Mousavi, Auteur ; Gregory C. Beroza, Auteur Année de publication : 2020 Article en page(s) : pp 8211 - 8224 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes descripteurs IGN] apprentissage profond [Termes descripteurs IGN] classification bayesienne [Termes descripteurs IGN] classification par réseau neuronal convolutif [Termes descripteurs IGN] détection du signal [Termes descripteurs IGN] épicentre [Termes descripteurs IGN] estimation bayesienne [Termes descripteurs IGN] onde sismique [Termes descripteurs IGN] régression [Termes descripteurs IGN] séisme [Termes descripteurs IGN] station d'observation [Termes descripteurs IGN] surveillance géologique [Termes descripteurs IGN] temps de propagation Résumé : (auteur) We present a deep-learning method for a single-station earthquake location, which we approach as a regression problem using two separate Bayesian neural networks. We use a multitask temporal convolutional neural network to learn epicentral distance and P travel time from 1-min seismograms. The network estimates epicentral distance and P travel time with mean errors of 0.23 km and 0.03 s and standard deviations of 5.42 km and 0.66 s, respectively, along with their epistemic and aleatory uncertainties. We design a separate multi-input network using standard convolutional layers to estimate the back-azimuth angle and its epistemic uncertainty. This network estimates the direction from which seismic waves arrive at the station with a mean error of 1°. Using this information, we estimate the epicenter, origin time, and depth along with their confidence intervals. We use a global data set of earthquake signals recorded within 1° (~112 km) from the event to build the model and demonstrate its performance. Our model can predict epicenter, origin time, and depth with mean errors of 7.3 km, 0.4 s, and 6.7 km, respectively, at different locations around the world. Our approach can be used for fast earthquake source characterization with a limited number of observations and also for estimating the location of earthquakes that are sparsely recorded—either because they are small or because stations are widely separated. Numéro de notice : A2020-684 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2020.2988770 date de publication en ligne : 06/05/2020 En ligne : https://doi.org/10.1109/TGRS.2020.2988770 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96209 [article]

Raytracing atmospheric delays in ground-based GNSS reflectometry / T. Nicolaidou in Journal of geodesy, vol 94 n° 8 (August 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 8 (August 2020) . - n° 68 Titre : Raytracing atmospheric delays in ground-based GNSS reflectometry Type de document : Article/Communication Auteurs : T. Nicolaidou, Auteur ; M.C. Santos, Auteur ; Simon D.P. Williams, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : n° 68 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] coin réflecteur [Termes descripteurs IGN] correction atmosphérique [Termes descripteurs IGN] lancer de rayons [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] réflectométrie par GNSS [Termes descripteurs IGN] réfraction [Termes descripteurs IGN] temps de propagation Résumé : (auteur) Several studies have recognized that Global Navigation Satellite System Reflectometry (GNSS-R) is subject to atmospheric propagation delays. Unfortunately, there is little information in the peer-reviewed literature about the methods and algorithms involved in correcting for this effect. We have developed an atmospheric ray-tracing procedure to solve rigorously the three-point boundary value problem of ground-based GNSS-R observations. We defined the reflection-minus-direct or interferometric delay in terms of vacuum distance and radio length. We clarified the roles of linear and angular refraction in splitting the total delay in two components, along-path and geometric. We have introduced for the first time two subcomponents of the atmospheric geometric delay, the geometry shift and the geometric excess. We have defined corresponding atmospheric altimetry corrections necessary for unbiased altimetry retrievals. Using simulations, we examined the interferometric atmospheric delay for a range of typical scenarios, where it attained centimeter-level values at low satellite elevation angles ~ 5° for a 10-m high station. We found a linear and exponential dependence on reflector height and satellite elevation angle, respectively. A similar trend was found for the atmospheric altimetry correction, albeit with an amplified meter-level magnitude. The two delay components were similar near the horizon while the angular one vanished at zenith. For the altimetry correction components, both remained non-zero at zenith. We thus quantified the atmospheric bias in GNSS-R sea level retrievals. Numéro de notice : A2020-538 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01390-8 date de publication en ligne : 23/07/2020 En ligne : https://doi.org/10.1007/s00190-020-01390-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95731 [article]

Modeling and sensing the vertical structure of the atmospheric path delay by microwave radiometry to correct SAR interferograms / Patrizia Basili in IEEE Transactions on geoscience and remote sensing, vol 52 n° 2 (February 2014)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 52 n° 2 (February 2014) . - pp 1324 - 1335 Titre : Modeling and sensing the vertical structure of the atmospheric path delay by microwave radiometry to correct SAR interferograms Type de document : Article/Communication Auteurs : Patrizia Basili, Auteur ; Stefania Bonafoni, Auteur ; Piero Ciotti, Auteur ; Nazzareno Pierdicca, Auteur Année de publication : 2014 Article en page(s) : pp 1324 - 1335 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes descripteurs IGN] correction atmosphérique [Termes descripteurs IGN] données localisées 3D [Termes descripteurs IGN] erreur de phase [Termes descripteurs IGN] image radar moirée [Termes descripteurs IGN] interféromètrie par radar à antenne synthétique [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] radiosondage [Termes descripteurs IGN] température de luminance [Termes descripteurs IGN] temps de propagation [Termes descripteurs IGN] teneur en vapeur d'eau Résumé : (Auteur) The vertical structure of the atmospheric water vapor induces phase errors in interferometric synthetic aperture radar (SAR) data. This paper presents a simulation study to investigate whether spaceborne submillimeter radiometric observations, which can be realized with fairly high spatial resolution, are able to derive the vertical structure of the atmospheric wet delay. The accuracy of the retrieved zenith wet delay (ZWD) trend as a function of surface height is assessed in order to correct the associated height dependence of the interferometric phase error in a SAR interferogram. Using a simulated benchmark, we evaluate the errors associated with the use of both a linear and an exponential model of the behavior of ZWD as a function of the surface height. This paper shows a fairly accurate reconstruction of the trend parameters estimated from radiometer brightness temperature images, with respect to realistic atmospheric profiles provided by radiosounding observations (RAOBs). The trend parameters that we consider in this paper are the slope K for the linear model and scale height H for the exponential one. An overall better accuracy is found for the exponential model, which is more representative of the actual behavior of ZWD with height, resulting in a residual uncertainty in the path delay due to the atmospheric stratification of approximately 0.2-0.3 cm and nearly zero bias, as compared to RAOBs. Numéro de notice : A2014-070 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2013.2250292 En ligne : https://doi.org/10.1109/TGRS.2013.2250292 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32975 [article]

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Monitoring precipitable water vapor in real-time using global navigation satellite systems / Seung-Woo Lee in Journal of geodesy, vol 87 n° 10-12 (October - December 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 10-12 (October - December 2013) . - pp 923 - 934 Titre : Monitoring precipitable water vapor in real-time using global navigation satellite systems Type de document : Article/Communication Auteurs : Seung-Woo Lee, Auteur ; Jan Kouba, Auteur ; Bob Schutz, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 923 - 934 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes descripteurs IGN] analyse diachronique [Termes descripteurs IGN] données GNSS [Termes descripteurs IGN] précipitation [Termes descripteurs IGN] surveillance météorologique [Termes descripteurs IGN] temps de propagation [Termes descripteurs IGN] temps réel [Termes descripteurs IGN] vapeur d'eau Résumé : (Auteur) This paper addresses real-time monitoring of the precipitable water vapor (PWV) from GNSS measurements and presents some results obtained from 6-month long GNSS PWV experiments using international and domestic GNSS networks. In the real-time GNSS PWV monitoring system a server/client structure is employed to facilitate formation of PWV networks and single-differenced GNSS measurements are utilized to mitigate errors in GNSS satellites’ orbits and clocks. An issue relating to baseline length between the server and clients is discussed in detail and as a result the PWV monitor is configured to perform in two modes depending on the baseline length. The server estimates sequentially the zenith wet delay of the individual stations, which is then converted into the PWV of the stations. We evaluate system performance by comparing the real-time PWV solution with reference solutions including meteorological measurements obtained with radiosondes and deferred-time precision GNSS PWV solutions. Results showed that the standard deviation of difference between the real-time PWV and the reference solutions ranged from 2.1 to 3.4 mm in PWV for a 6-month long comparison, which was improved to 1.4 to 2.9 mm by reducing comparison period to 20 days in winter. Numéro de notice : A2013-667 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0655-y date de publication en ligne : 11/08/2013 En ligne : https://doi.org/10.1007/s00190-013-0655-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32803 [article]

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A method for improving uncalibrated phase delay estimation and ambiguity-fixing in real-time precise point positioning / Xinging Li in Journal of geodesy, vol 87 n° 5 (May 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 5 (May 2013) . - pp 405 - 416 Titre : A method for improving uncalibrated phase delay estimation and ambiguity-fixing in real-time precise point positioning Type de document : Article/Communication Auteurs : Xinging Li, Auteur ; Maorong Ge, Auteur Année de publication : 2013 Article en page(s) : pp 405 - 416 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] ambiguïté entière [Termes descripteurs IGN] atténuation du signal [Termes descripteurs IGN] mesurage de phase [Termes descripteurs IGN] positionnement ponctuel précis [Termes descripteurs IGN] propagation ionosphérique [Termes descripteurs IGN] résolution d'ambiguïté [Termes descripteurs IGN] temps de propagation [Termes descripteurs IGN] temps réel Résumé : (Auteur) In order to improve the performance of precise point positioning (PPP), this paper presents a new data processing scheme to shorten the convergence time and the observation time required for a reliable ambiguity-fixing. In the new scheme, L1 and L2 raw observations are used and the slant ionospheric delays are treated as unknown parameters. The empirical spatial and temporal constraints and the ionospheric delays derived from a real-time available ionospheric model are all considered as pseudo-observations into the estimation for strengthening the solution. Furthermore, we develop a real-time computational procedure for generating uncalibrated phase delays (UPDs) on L1 and L2 frequencies. The PPP solution is first carried out on all reference stations based on the proposed scheme, undifferenced float ambiguities on L1 and L2 frequencies can be directly obtained from the new scheme. The L1 and L2 UPDs are then generated and broadcasted to users in real-time. This data product and also the performance of the new PPP scheme are evaluated. Our results indicate that the new processing scheme considering ionospheric characteristics can reduce the convergence time by about 30 % for float kinematic solutions. The observation time for a reliable ambiguity-fixing is shortened by 25 % compared to that of the traditional ambiguity-fixed kinematic solution. When the new method is used for static reference stations, the observation time for ambiguity-fixing is about 10 min in static mode and only 5 min if the coordinates are fixed to well-known values. Numéro de notice : A2013-251 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0611-x En ligne : https://link.springer.com/article/10.1007/s00190-013-0611-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32389 [article]

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Time, atomics clocks and relativistic geodesy / Enrico Mai (2013)

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Modelling and compensating internal light scattering in time of flight range cameras / Wilfiried Karel in Photogrammetric record, vol 27 n° 138 (June - August 2012)  

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Rapport du directeur sur l'activité et la gestion du Bureau International des Poids et Mesures (BIPM), 1er juillet 2009 - 30 juin 2010 / Bureau international des poids et mesures (2011)

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Rapport du directeur sur l'activité et la gestion du Bureau international des poids et mesures (BIPM), 1er juillet 2008 - 30 juin 2009 / Bureau international des poids et mesures (2009)

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Rapport du directeur sur l'activité et la gestion du Bureau International des Poids et Mesures (BIPM), 1er juillet 2007 - 30 juin 2008 / Bureau international des poids et mesures (2008)

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Rapport du directeur sur l'activité et la gestion du Bureau International des Poids et Mesures (BIPM), 1er juillet 2006 - 30 juin 2007 / Bureau international des poids et mesures (2007)

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Practical satellite navigation: part 2 GPS position and time determination / H. Lekkerkerk in Geoinformatics, vol 9 n° 2 (01/03/2006)

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Ground-penetrating radar measurement of crop and surface water content dynamics / G. Serbin in Remote sensing of environment, vol 96 n° 1 (15/05/2005)

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Techniques GPS-RTK appliquées à la trajectographie / Hervé Gontran in XYZ, n° 99 (juin - août 2004)

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Large deviation theorems for weighted sums applied to a geographical problem / Olivier Bonin in Journal of Applied Probability, vol 39 n° 2 (01/06/2002)  

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