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A hybrid approach for recovering high-resolution temporal gravity fields from satellite laser ranging / Anno Löcher in Journal of geodesy, vol 95 n° 1 (January 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 1 (January 2021) . - n° 6 Titre : A hybrid approach for recovering high-resolution temporal gravity fields from satellite laser ranging Type de document : Article/Communication Auteurs : Anno Löcher, Auteur ; Jürgen Kusche, Auteur Année de publication : 2021 Article en page(s) : n° 6 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] changement temporel [Termes IGN] données GRACE [Termes IGN] données TLS (télémétrie) [Termes IGN] facteur d'échelle [Termes IGN] fonction orthogonale [Termes IGN] harmonique sphérique [Termes IGN] modélisation [Termes IGN] série temporelle Résumé : (auteur) A new approach to recover time-variable gravity fields from satellite laser ranging (SLR) is presented. It takes up the concept of lumped coefficients by representing the temporal changes of the Earth’s gravity field by spatial patterns via combinations of spherical harmonics. These patterns are derived from the GRACE mission by decomposing the series of monthly gravity field solutions into empirical orthogonal functions (EOFs). The basic idea of the approach is then to use the leading EOFs as base functions in the gravity field modelling and to adjust the respective scaling factors straightforward within the dynamic orbit computation; only for the lowest degrees, the spherical harmonic coefficients are estimated separately. As a result, the estimated gravity fields have formally the same spatial resolution as GRACE. It is shown that, within the GRACE time frame, both the secular and the seasonal signals in the GRACE time series are reproduced with high accuracy. In the period prior to GRACE, the SLR solutions are in good agreement with other techniques and models and confirm, for instance, that the Greenland ice sheet was stable until the late 1990s. Further validation is done with the first monthly fields from GRACE Follow-On, showing a similar agreement as with GRACE itself. Significant differences to the reference data only emerge occasionally when zooming into smaller river basins with strong interannual mass variations. In such cases, the approach reaches its limits which are set by the low spectral sensitivity of the SLR satellites and the strong constraints exerted by the EOFs. The benefit achieved by the enhanced spatial resolution has to be seen, therefore, primarily in the proper capturing of the mass signal in medium or large areas rather than in the opportunity to focus on isolated spatial details. Numéro de notice : A2021-026 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01460-x Date de publication en ligne : 23/12/2020 En ligne : https://doi.org/10.1007/s00190-020-01460-x Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96710 [article]

The construction of sound speed field based on back propagation neural network in the global ocean / Junting Wang in Marine geodesy, vol 43 n° 6 (November 2020)  

Public [article]  inMarine geodesy > vol 43 n° 6 (November 2020) . - pp 621 - 642 Titre : The construction of sound speed field based on back propagation neural network in the global ocean Type de document : Article/Communication Auteurs : Junting Wang, Auteur ; Tianhe Xu, Auteur ; Wenfeng Nie, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 621 - 642 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] fonction orthogonale [Termes IGN] interpolation spatiale [Termes IGN] milieu marin [Termes IGN] onde acoustique [Termes IGN] propagation du son [Termes IGN] réseau neuronal artificiel [Termes IGN] salinité [Termes IGN] sondage acoustique [Termes IGN] température [Termes IGN] vitesse Résumé : (auteur) The sound speed is a key parameter that affects the underwater acoustic positioning and navigation. Aiming at the high-precision construction of sound speed field in the complex marine environment, this paper proposes a sound speed field model based on back propagation neural network (BPNN) by considering the correlation of learning samples. The method firstly uses measured ocean parameters to construct the temperature and salinity field. Then the spatial position, the temperature and the salinity information are used to construct the global ocean sound speed field based on the back propagation neural network algorithm. During the processing, the learning samples of back propagation neural network are selected based on the correlation between sound speed and distance. The proposed algorithm is validated by the global Argo data as well as compared with the spatial interpolation and the empirical orthogonal function (EOF) algorithm. The results demonstrate that the average root mean squares of the BPNN considering the correlation of learning samples is 0.352 m/s compared to the 1.527 m/s of EOF construction and the 2.661 m/s of spatial interpolation, with an improvement of 76.9% and 86.8%. Therefore, the proposed algorithm can improve the construction accuracy of sound speed field in the complex marine environment. Numéro de notice : A2020-694 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01490419.2020.1815912 Date de publication en ligne : 14/09/2020 En ligne : https://doi.org/10.1080/01490419.2020.1815912 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96242 [article]

Characterization of ionospheric variability in TEC using EOF and wavelets over low-latitude GNSS stations / J.R.K. Kumar Dabbakuti in Advances in space research, vol 57 n° 12 (June 2016)  

Public [article]  inAdvances in space research > vol 57 n° 12 (June 2016) . - pp 2427 – 2443 Titre : Characterization of ionospheric variability in TEC using EOF and wavelets over low-latitude GNSS stations Type de document : Article/Communication Auteurs : J.R.K. Kumar Dabbakuti, Auteur ; D. Venkata Ratman, Auteur Année de publication : 2016 Article en page(s) : pp 2427 – 2443 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] coordonnées GPS [Termes IGN] fonction orthogonale [Termes IGN] International Reference Ionosphere [Termes IGN] retard ionosphèrique [Termes IGN] teneur totale en électrons [Termes IGN] transformation en ondelettes Résumé : (auteur) Investigation of ionospheric variability is essential for improving the daily ionospheric modeling and forecasting services of Global Navigation Satellite System (GNSS) applications. As India is a low-latitude region, more care has to be taken here to characterize the ionosphere due to irregularities and Equatorial Ionization Anomaly (EIA) conditions. Therefore, an appropriate method is required to diagnose the ionospheric variations during geomagnetic, solar and other disturbances. In this paper, the temporal ionospheric time delay variations were studied based on the Empirical Orthogonal Function (EOF) analysis and wavelet transforms (WT).These analyses were carried out with Total Electron Content (TEC) datasets obtained from three GNSS stations located in low-latitude regions. EOF analysis was performed on the TEC datasets, which were decomposed into a time series of orthogonal eigen values (or base functions) and associated coefficients. EOF base functions and their associated coefficients signify the hourly time variations and the day of the year variations. The results reveal that the first few EOFs represented the majority of TEC variability pertaining to the physical processes of the ionosphere. The accuracy of the EOF model was validated by the evaluation of observational TEC data with International Reference Ionosphere (IRI) 2012 models. The EOF model coefficients for each GNSS station showed a strong correlation with the IRI models and also described the correlation between the impacts of the level of geomagnetic activity on the ionosphere. The correlation coefficients for the first three EOFs were more than 0.95. The phase relationship of ionospheric TEC anomalies, with respect to the geomagnetic indices (Dst), were analyzed by wavelet transforms. Numéro de notice : A2016-267 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2016.03.029 En ligne : https://doi.org/10.1016/j.asr.2016.03.029 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80802 [article]

Advanced spatio-temporal filtering techniques for photogrammetric image sequence analysis in civil engineering material testing / F. Liebold in ISPRS Journal of photogrammetry and remote sensing, vol 111 (January 2016)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 111 (January 2016) . - pp 13 – 21 Titre : Advanced spatio-temporal filtering techniques for photogrammetric image sequence analysis in civil engineering material testing Type de document : Article/Communication Auteurs : F. Liebold, Auteur ; Hans-Gerd Maas, Auteur Année de publication : 2016 Article en page(s) : pp 13 – 21 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] filtrage du bruit [Termes IGN] fonction orthogonale [Termes IGN] mesure géométrique [Termes IGN] séquence d'images Résumé : (auteur) The paper shows advanced spatial, temporal and spatio-temporal filtering techniques which may be used to reduce noise effects in photogrammetric image sequence analysis tasks and tools. As a practical example, the techniques are validated in a photogrammetric spatio-temporal crack detection and analysis tool applied in load tests in civil engineering material testing. The load test technique is based on monocular image sequences of a test object under varying load conditions. The first image of a sequence is defined as a reference image under zero load, wherein interest points are determined and connected in a triangular irregular network structure. For each epoch, these triangles are compared to the reference image triangles to search for deformations. The result of the feature point tracking and triangle comparison process is a spatio-temporally resolved strain value field, wherein cracks can be detected, located and measured via local discrepancies. The strains can be visualized as a color-coded map. In order to improve the measuring system and to reduce noise, the strain values of each triangle must be treated in a filtering process. The paper shows the results of various filter techniques in the spatial and in the temporal domain as well as spatio-temporal filtering techniques applied to these data. The best results were obtained by a bilateral filter in the spatial domain and by a spatio-temporal EOF (empirical orthogonal function) filtering technique. Numéro de notice : A2016-037 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2015.10.013 Date de publication en ligne : 01/12/2015 En ligne : https://doi.org/10.1016/j.isprsjprs.2015.10.013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79516 [article]

Ionospheric modeling using GPS: Greater fidelity using a 3D approach / Wei Zhang in GPS world, vol 25 n° 2 (February 2014)

Public [article]  inGPS world > vol 25 n° 2 (February 2014) . - pp 59 - 65 Titre : Ionospheric modeling using GPS: Greater fidelity using a 3D approach Type de document : Article/Communication Auteurs : Wei Zhang, Auteur ; Attila Komjathy, Auteur ; Simon Banville, Auteur ; Richard B. Langley, Auteur Année de publication : 2014 Article en page(s) : pp 59 - 65 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] données localisées 3D [Termes IGN] fonction orthogonale [Termes IGN] modèle ionosphérique [Termes IGN] signal GPS [Termes IGN] temps réel Résumé : (Auteur) In this month's column, we look at the performance of this 3D approach to modeling the ionosphere including times when the ionosphere is particularly interesting. Numéro de notice : A2014-096 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33001 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
067-2014021	RAB	Revue	Centre de documentation	En réserve L003	Disponible

The spherical Slepian basis as a means to obtain spectral consistency between mean sea level and the geoid / D. Slobbe in Journal of geodesy, vol 86 n° 8 (August 2012)  

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Reconstruction des séries marégraphiques de la mer du Nord et de Norvège / Raphaël Baucry (2012) 

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Orthoimage creation of extremely high buildings / Guoqing Zhou in IEEE Transactions on geoscience and remote sensing, vol 46 n° 12 (December 2008)  

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Orthogonal functions over the oceans and applications to the determination of orbit error, geoid and sea surface topography from satellite altimetry / C. Hwang (1991)

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Geometric correction of remotely-sensed imagery using ground control points and orthogonal polynomials / A.J. DE Leeuw in International Journal of Remote Sensing IJRS, vol 9 n°10-11 (October-November 1988)  

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Fonctions orthogonales dans la sphère : résolution théorique du problème du potentiel terrestre / Henri Marcel Dufour (01/03/1976)

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