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Vertical and horizontal spheroidal boundary-value problems / Michal Šprlák in Journal of geodesy, vol 92 n° 7 (July 2018)  

Public [article]  inJournal of geodesy > vol 92 n° 7 (July 2018) . - pp 811 - 826 Titre : Vertical and horizontal spheroidal boundary-value problems Type de document : Article/Communication Auteurs : Michal Šprlák, Auteur ; Natthachet Tangdamrongsub, Auteur Année de publication : 2018 Article en page(s) : pp 811 - 826 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] analyse harmonique [Termes descripteurs IGN] gradient de gravitation [Termes descripteurs IGN] problème des valeurs limites [Termes descripteurs IGN] sphèroïde Résumé : (Auteur) Vertical and horizontal spheroidal boundary-value problems (BVPs), i.e., determination of the external gravitational potential from the components of the gravitational gradient on the spheroid, are discussed in this article. The gravitational gradient is decomposed into the series of the vertical and horizontal vector spheroidal harmonics, before being orthogonalized in a weighted sense by two different approaches. The vertical and horizontal spheroidal BVPs are then formulated and solved in the spectral and spatial domains. Both orthogonalization methods provide the same analytical solutions for the vertical spheroidal BVP, and give distinct, but equivalent, analytical solutions for the horizontal spheroidal BVP. A closed-loop simulation is performed to test the correctness of the analytical solutions, and we investigate analytical properties of the sub-integral kernels. The systematic treatment of the spheroidal BVPs and the resulting mathematical equations extend the theoretical apparatus of geodesy and of the potential theory. Numéro de notice : A2018-455 Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1096-9 date de publication en ligne : 07/12/2017 En ligne : https://doi.org/10.1007/s00190-017-1096-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91046 [article]

Toward a global horizontal and vertical elastic load deformation model derived from GRACE and GNSS station position time series / Kristel Chanard in Journal of geophysical research : Solid Earth, vol 123 n° 4 (April 2018)  

Public [article]  inJournal of geophysical research : Solid Earth > vol 123 n° 4 (April 2018) . - pp Titre : Toward a global horizontal and vertical elastic load deformation model derived from GRACE and GNSS station position time series Type de document : Article/Communication Auteurs : Kristel Chanard , Auteur ; Luce Fleitout, Auteur ; Eric Calais, Auteur ; Paul Rebischung , Auteur ; Jean-Philippe Avouac, Auteur Année de publication : 2018 Article en page(s) : pp Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] coordonnées GNSS [Termes descripteurs IGN] déformation horizontale de la croute terrestre [Termes descripteurs IGN] déformation verticale de la croute terrestre [Termes descripteurs IGN] données GRACE [Termes descripteurs IGN] Earth Gravity Model 2008 [Termes descripteurs IGN] erreur systématique [Termes descripteurs IGN] harmonique sphérique [Termes descripteurs IGN] modèle de déformation tectonique [Termes descripteurs IGN] mouvement du géocentre [Termes descripteurs IGN] série temporelle Résumé : (Auteur) We model surface displacements induced by variations in continental water, atmospheric pressure, and non‐tidal oceanic loading, derived from the Gravity and Recovery Climate Experiment (GRACE) for spherical harmonic degrees two and higher. As they are not observable by GRACE, we use at first the degree‐1 spherical harmonic coefficients from (Swenson2008estimating). We compare the predicted displacements with the position time series of 689 globally distributed continuous Global Navigation Satellite System (GNSS) stations. While GNSS vertical displacements are well explained by the model at a global scale, horizontal displacements are systematically underpredicted and out‐of‐phase with GNSS station position time series. We then re‐estimate the degree‐1 deformation field from a comparison between our GRACE‐derived model, with no a priori degree‐1 loads, and the GNSS observations. We show that this approach reconciles GRACE‐derived loading displacements and GNSS station position time series at a global scale, particularly in the horizontal components. Assuming that they reflect surface loading deformation only, our degree‐1 estimates can be translated into geocenter motion time series. We also address and assess the impact of systematic errors in GNSS station position time series at the Global Positioning System (GPS) draconitic period and its harmonics on the comparison between GNSS and GRACE‐derived annual displacements. Our results confirm that surface mass redistributions observed by GRACE, combined with an elastic spherical and layered Earth model, can be used to provide first order corrections for loading deformation observed in both horizontal and vertical components of GNSS station position time series. Numéro de notice : A2018-055 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1002/2017JB015245 date de publication en ligne : 21/02/2018 En ligne : https://doi.org/10.1002/2017JB015245 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89382 [article]

Transformation between surface spherical harmonic expansion of arbitrary high degree and order and double Fourier series on sphere / Toshio Fukushima in Journal of geodesy, vol 92 n° 2 (February 2018)  

Public [article]  inJournal of geodesy > vol 92 n° 2 (February 2018) . - pp 123 - 130 Titre : Transformation between surface spherical harmonic expansion of arbitrary high degree and order and double Fourier series on sphere Type de document : Article/Communication Auteurs : Toshio Fukushima, Auteur Année de publication : 2018 Article en page(s) : pp 123 - 130 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie [Termes descripteurs IGN] harmonique sphérique [Termes descripteurs IGN] série de Fourier [Termes descripteurs IGN] transformation géométrique [Termes descripteurs IGN] transformation inverse Résumé : (Auteur) In order to accelerate the spherical harmonic synthesis and/or analysis of arbitrary function on the unit sphere, we developed a pair of procedures to transform between a truncated spherical harmonic expansion and the corresponding two-dimensional Fourier series. First, we obtained an analytic expression of the sine/cosine series coefficient of the 4π fully normalized associated Legendre function in terms of the rectangle values of the Wigner d function. Then, we elaborated the existing method to transform the coefficients of the surface spherical harmonic expansion to those of the double Fourier series so as to be capable with arbitrary high degree and order. Next, we created a new method to transform inversely a given double Fourier series to the corresponding surface spherical harmonic expansion. The key of the new method is a couple of new recurrence formulas to compute the inverse transformation coefficients: a decreasing-order, fixed-degree, and fixed-wavenumber three-term formula for general terms, and an increasing-degree-and-order and fixed-wavenumber two-term formula for diagonal terms. Meanwhile, the two seed values are analytically prepared. Both of the forward and inverse transformation procedures are confirmed to be sufficiently accurate and applicable to an extremely high degree/order/wavenumber as 230≈109. The developed procedures will be useful not only in the synthesis and analysis of the spherical harmonic expansion of arbitrary high degree and order, but also in the evaluation of the derivatives and integrals of the spherical harmonic expansion. Numéro de notice : A2018-057 Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1049-3 En ligne : https://doi.org/10.1007/s00190-017-1049-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89390 [article]

Extension of satellite altimetry Jason-2 sea level anomalies towards the Red Sea coast using polynomial harmonic techniques / A. M. Taqi in Marine geodesy, vol 40 n° 5 (September 2017)  

Public [article]  inMarine geodesy > vol 40 n° 5 (September 2017) . - pp 315 - 328 Titre : Extension of satellite altimetry Jason-2 sea level anomalies towards the Red Sea coast using polynomial harmonic techniques Type de document : Article/Communication Auteurs : A. M. Taqi, Auteur ; A. M. Al-Subhi, Auteur ; M. A. Alsaafani, Auteur Année de publication : 2017 Article en page(s) : pp 315 - 328 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Nivellement [Termes descripteurs IGN] altimétrie satellitaire par radar [Termes descripteurs IGN] AVISO [Termes descripteurs IGN] données altimétriques [Termes descripteurs IGN] données Jason [Termes descripteurs IGN] équation polynomiale [Termes descripteurs IGN] fonction harmonique [Termes descripteurs IGN] littoral [Termes descripteurs IGN] niveau de la mer [Termes descripteurs IGN] Rouge, mer [Termes descripteurs IGN] série de Fourier Résumé : (Auteur) Satellite altimetry data are facing big challenges near the coasts. These challenges arise due to the fundamental difficulties of correction and land contamination in the foot print, which result in rejection of these data near the coast. Several studies have been carried out to extend these data towards the coast. Over the Red Sea, altimetry data consist of gaps, which extend to about 30–50 km from the coast. Two methods are used for processing and extending Jason-2 satellite altimetry sea level anomalies (SLAs) towards the Red Sea coast; Fourier Series Model (FSM), and the polynomial sum of sine model (SSM). FSM model technique uses Fourier series and statistical analysis reflects strong relationship with both the observation and AVISO data, with strong and positive correlation. The second prediction technique, SSM model, depends on the polynomial sum of sine, and does not reflect any relationship with the observations and AVISO data close to the coast and the correlation coefficient (CC) is weak and negative. The FSM model output results in SLA data significantly better and more accurate than the SSM model output. Numéro de notice : A2017-668 Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2017.1333549 En ligne : https://doi.org/10.1080/01490419.2017.1333549 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=87143 [article]

Extracting urban functional regions from points of interest and human activities on location-based social networks / Song Gao in Transactions in GIS, vol 21 n° 3 (June 2017)  

Public [article]  inTransactions in GIS > vol 21 n° 3 (June 2017) . - pp 446 - 467 Titre : Extracting urban functional regions from points of interest and human activities on location-based social networks Type de document : Article/Communication Auteurs : Song Gao, Auteur ; Krzysztof Janowicz, Auteur ; Helen Couclelis, Auteur Année de publication : 2017 Article en page(s) : pp 446 - 467 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes descripteurs IGN] classification par nuées dynamiques [Termes descripteurs IGN] connaissance thématique [Termes descripteurs IGN] Etats-Unis [Termes descripteurs IGN] point d'intérêt [Termes descripteurs IGN] problème de Dirichlet [Termes descripteurs IGN] réseau social géodépendant [Termes descripteurs IGN] trace GPS [Termes descripteurs IGN] triangulation de Delaunay [Termes descripteurs IGN] zone urbaine Résumé : (Auteur) Data about points of interest (POI) have been widely used in studying urban land use types and for sensing human behavior. However, it is difficult to quantify the correct mix or the spatial relations among different POI types indicative of specific urban functions. In this research, we develop a statistical framework to help discover semantically meaningful topics and functional regions based on the co-occurrence patterns of POI types. The framework applies the latent Dirichlet allocation (LDA) topic modeling technique and incorporates user check-in activities on location-based social networks. Using a large corpus of about 100,000 Foursquare venues and user check-in behavior in the 10 most populated urban areas of the US, we demonstrate the effectiveness of our proposed methodology by identifying distinctive types of latent topics and, further, by extracting urban functional regions using K-means clustering and Delaunay triangulation spatial constraints clustering. We show that a region can support multiple functions but with different probabilities, while the same type of functional region can span multiple geographically non-adjacent locations. Since each region can be modeled as a vector consisting of multinomial topic distributions, similar regions with regard to their thematic topic signatures can be identified. Compared with remote sensing images which mainly uncover the physical landscape of urban environments, our popularity-based POI topic modeling approach can be seen as a complementary social sensing view on urban space based on human activities. Numéro de notice : A2017-623 Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/tgis.12289 En ligne : http://dx.doi.org/10.1111/tgis.12289 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86938 [article]

Computationally efficient hyperspectral data learning based on the doubly stochastic dirichlet process / Xing Sun in IEEE Transactions on geoscience and remote sensing, vol 55 n° 1 (January 2017)  

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Discriminative-dictionary-learning-based multilevel point-cluster features for ALS point-cloud classification / Zhenxin Zhang in IEEE Transactions on geoscience and remote sensing, vol 54 n° 12 (December 2016)  

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On the spectral combination of satellite gravity model, terrestrial and airborne gravity data for local gravimetric geoid computation / Tao Jian in Journal of geodesy, vol 90 n° 12 (December 2016)  

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Dirichlet process based active learning and discovery of unknown classes for hyperspectral image classification / Hao Wu in IEEE Transactions on geoscience and remote sensing, vol 54 n° 8 (August 2016)  

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Contribution of mass density heterogeneities to the quasigeoid-to-geoid separation / Robert Tenzer in Journal of geodesy, vol 90 n° 1 (January 2016)  

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Traitement du signal marégraphique par analyse harmonique pour la détermination d'une référence altimétrique pour l'Algérie / A. Rami in Bulletin des sciences géographiques, n° 30 (2015 - 2016)

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A moving weighted harmonic analysis method for reconstructing high-quality SPOT VEGETATION NDVI time-series data / Gang Yang in IEEE Transactions on geoscience and remote sensing, vol 53 n° 11 (November 2015)

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A surface spherical harmonic expansion of gravity anomalies on the ellipsoid / S.J. Claessens in Journal of geodesy, vol 89 n° 10 (october 2015)  

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Reducing leakage error in GRACE-observed long-term ice mass change: a case study in West Antarctica / J. L. Chen in Journal of geodesy, vol 89 n° 9 (september 2015)  

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Accuracy of unmodified Stokes’ integration in the R-C-R procedure for geoid computation / Zahra Ismaïl in Journal of applied geodesy, vol 9 n° 2 (June 2015)  

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