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Gravitational field modelling near irregularly shaped bodies using spherical harmonics: a case study for the asteroid (101955) Bennu / Blažej Bucha in Journal of geodesy, vol 95 n° 5 (May 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 5 (May 2021) . - n° 56 Titre : Gravitational field modelling near irregularly shaped bodies using spherical harmonics: a case study for the asteroid (101955) Bennu Type de document : Article/Communication Auteurs : Blažej Bucha, Auteur ; Fernando Sanso, Auteur Année de publication : 2021 Article en page(s) : n° 56 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] astéroïde [Termes descripteurs IGN] champ de gravitation [Termes descripteurs IGN] champ de pesanteur terrestre [Termes descripteurs IGN] convergence [Termes descripteurs IGN] harmonique sphérique [Termes descripteurs IGN] intégrale de Newton Résumé : (auteur) We apply three spherical-harmonic-based techniques to deliver external gravitational field models of the asteroid (101955) Bennu within its circumscribing sphere. This region is known to be peculiar for external spherical harmonic expansions, because it may lead to a divergent series. The studied approaches are (i) spectral gravity forward modelling via external spherical harmonics, (ii) the least-squares estimation from surface gravitational data using external spherical harmonics and (iii) the combination of internal and external series expansions. While the first method diverges beyond any reasonable doubts, we show that the other two methods may ensure relative accuracy from ∼10−6 to 10−8 in the vicinity of Bennu. This is possible even with the second method, despite the fact that it relies on a single series of external spherical harmonics. Our main motivation was to study conceptual differences between spherical harmonic coefficients from satellite data (analogy to the first method) and from surface gravitational data (the second method). Such coefficients are available through the popular spherical-harmonic-based models of the Earth’s gravitational field and often are combined together. We show that the coefficients from terrestrial data may lead to a divergence effect of partial sums, though excellent accuracy can be achieved when such model is used in full. Under (presently) extreme but realistic conditions, the divergence effect of partial sums may affect many near-surface geoscientific applications, such as the geoid/quasigeoid computation or residual terrain modelling. Computer codes (Fortran, MATLAB) and data produced within the study are made freely available at http://edisk.cvt.stuba.sk/~xbuchab/. Numéro de notice : A2021-347 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01493-w date de publication en ligne : 22/04/2021 En ligne : https://doi.org/10.1007/s00190-021-01493-w Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97591 [article]

Pléiades Neo, 4 satellites réactifs / Laurent Polidori in Géomètre, n° 2191 (mai 2021)

Public [article]  inGéomètre > n° 2191 (mai 2021) . - pp 11 - 11 Titre : Pléiades Neo, 4 satellites réactifs Type de document : Article/Communication Auteurs : Laurent Polidori, Auteur Année de publication : 2021 Article en page(s) : pp 11 - 11 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Technologies spatiales [Termes descripteurs IGN] image Pléiades-Neo [Termes descripteurs IGN] observation de la Terre [Termes descripteurs IGN] orbite héliosynchrone [Termes descripteurs IGN] Pléiades (mission) [Termes descripteurs IGN] précision décamétrique [Termes descripteurs IGN] secteur spatial Résumé : (Auteur) Trente minutes après le passage des satellites de la constellation Pléiades Neo, les images en résolution décamétrique seront sur l'ordinateur des utilisateurs ! Numéro de notice : A2021-363 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtSansCL DOI : sans date de publication en ligne : 05/05/2021 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97652 [article]

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Understanding collective human movement dynamics during large-scale events using big geosocial data analytics / Junchuan Fan in Computers, Environment and Urban Systems, vol 87 (May 2021)  

Public [article]  inComputers, Environment and Urban Systems > vol 87 (May 2021) . - n° 101605 Titre : Understanding collective human movement dynamics during large-scale events using big geosocial data analytics Type de document : Article/Communication Auteurs : Junchuan Fan, Auteur ; Kathleen Stewart, Auteur Année de publication : 2021 Article en page(s) : n° 101605 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes descripteurs IGN] collecte de données [Termes descripteurs IGN] données GPS [Termes descripteurs IGN] données issues des réseaux sociaux [Termes descripteurs IGN] données localisées des bénévoles [Termes descripteurs IGN] données massives [Termes descripteurs IGN] dynamique spatiale [Termes descripteurs IGN] échantillonnage de données [Termes descripteurs IGN] éclipse solaire [Termes descripteurs IGN] estimation par noyau [Termes descripteurs IGN] Etats-Unis [Termes descripteurs IGN] événement [Termes descripteurs IGN] géolocalisation [Termes descripteurs IGN] migration humaine [Termes descripteurs IGN] mobilité territoriale [Termes descripteurs IGN] téléphonie mobile Résumé : (auteur) Conventional approaches for modeling human mobility pattern often focus on human activity and movement dynamics in their regular daily lives and cannot capture changes in human movement dynamics in response to large-scale events. With the rapid advancement of information and communication technologies, many researchers have adopted alternative data sources (e.g., cell phone records, GPS trajectory data) from private data vendors to study human movement dynamics in response to large-scale natural or societal events. Big geosocial data such as georeferenced tweets are publicly available and dynamically evolving as real-world events are happening, making it more likely to capture the real-time sentiments and responses of populations. However, precisely-geolocated geosocial data is scarce and biased toward urban population centers. In this research, we developed a big geosocial data analytical framework for extracting human movement dynamics in response to large-scale events from publicly available georeferenced tweets. The framework includes a two-stage data collection module that collects data in a more targeted fashion in order to mitigate the data scarcity issue of georeferenced tweets; in addition, a variable bandwidth kernel density estimation(VB-KDE) approach was adopted to fuse georeference information at different spatial scales, further augmenting the signals of human movement dynamics contained in georeferenced tweets. To correct for the sampling bias of georeferenced tweets, we adjusted the number of tweets for different spatial units (e.g., county, state) by population. To demonstrate the performance of the proposed analytic framework, we chose an astronomical event that occurred nationwide across the United States, i.e., the 2017 Great American Eclipse, as an example event and studied the human movement dynamics in response to this event. However, this analytic framework can easily be applied to other types of large-scale events such as hurricanes or earthquakes. Numéro de notice : A2021-275 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/SOCIETE NUMERIQUE Nature : Article DOI : 10.1016/j.compenvurbsys.2021.101605 date de publication en ligne : 05/02/2021 En ligne : https://doi.org/10.1016/j.compenvurbsys.2021.101605 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97358 [article]

Integer phase clock method with single-satellite ambiguity fixing and its application in LEO satellite orbit determination / Kai Shao in Acta Geodaetica et Cartographica Sinica, vol 50 n° 4 ([20/04/2021])  

Public [article]  inActa Geodaetica et Cartographica Sinica > vol 50 n° 4 [20/04/2021] . - pp 487 - 495 Titre : Integer phase clock method with single-satellite ambiguity fixing and its application in LEO satellite orbit determination Type de document : Article/Communication Auteurs : Kai Shao, Auteur ; Bin Yi, Auteur ; Houzhe Zhang, Auteur ; Defeng Gu, Auteur Année de publication : 2021 Article en page(s) : pp 487 - 495 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] bande K [Termes descripteurs IGN] orbite basse [Termes descripteurs IGN] orbitographie [Termes descripteurs IGN] phase [Termes descripteurs IGN] phase GNSS [Termes descripteurs IGN] résolution d'ambiguïté Résumé : (auteur) Fixing single-satellite GPS carrier phase ambiguity could significantly improve the orbit accuracy of low earth orbit (LEO) satellite. Currently, the CNES/CLS, Wuhan University and CODE have published GPS integer phase clock products applied to single-satellite ambiguity fixing. In this paper, the integer phase clock method is used for single-satellite ambiguity fixing, and it is applied to the precise orbit determination of LEO satellite. Then, the application performances of integer phase clock products provided by different agencies in single-satellite ambiguity fixing and LEO satellite orbit determination are compared and analyzed. For GRACE-FO formation satellites, about 94% ambiguities could be fixed based on different products provided by the three agencies. Orbit solutions generated using the products from the three agencies can achieve an RMS of around 0.9 cm checked by satellite laser ranging data. Compared with ambiguity-float orbit solutions, the accuracy of absolute orbit determination with single-satellite ambiguity fixing is improved by about 30%. After fixing single-satellite ambiguities using the different products provided by CNES/CLS, WHU and CODE, respectively, the RMS of K-band ranging validation residuals for relative orbit solutions are reduced from 5.7, 5.4 and 5.3 mm to 2.1、 2.0 and 1.5 mm, respectively. The results show that the integer phase clock products provided by different agencies have similar performances in the single-satellite ambiguity fixing and orbit determination of GRACE-FO satellite. Numéro de notice : A2021-310 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.11947/j.AGCS.2021.20200302 date de publication en ligne : 20/04/2021 En ligne : https://doi.org/10.11947/j.AGCS.2021.20200302 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97755 [article]

Automatic atmospheric correction for shortwave hyperspectral remote sensing data using a time-dependent deep neural network / Jian Sun in ISPRS Journal of photogrammetry and remote sensing, vol 174 (April 2021)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 174 (April 2021) . - pp 117 - 131 Titre : Automatic atmospheric correction for shortwave hyperspectral remote sensing data using a time-dependent deep neural network Type de document : Article/Communication Auteurs : Jian Sun, Auteur ; Fangcao Xu, Auteur ; Guido Cervone, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 117 - 131 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes descripteurs IGN] apprentissage profond [Termes descripteurs IGN] classification par réseau neuronal convolutif [Termes descripteurs IGN] correction atmosphérique [Termes descripteurs IGN] détection de cible [Termes descripteurs IGN] image hyperspectrale [Termes descripteurs IGN] modèle de transfert radiatif [Termes descripteurs IGN] rayonnement solaire [Termes descripteurs IGN] réflectivité Résumé : (auteur) Atmospheric correction is an essential step in hyperspectral imaging and target detection from spectrometer remote sensing data. State-of-the-art atmospheric correction approaches either require extensive filed experiments or prior knowledge of atmospheric characteristics to improve the predicted accuracy, which are computational expensive and unsuitable for real time application. To take full advantages of remote sensing observation in quickly and reliably acquiring data for a large area, an automatic and efficient processing tool is required for atmospheric correction. In this paper, we propose a time-dependent neural network for automatic atmospheric correction and target detection using multi-scan hyperspectral data under different elevation angles. In addition to the total radiance, the collection day and time are also incorporated to improve the time-dependency of the network and represent the seasonal and diurnal characteristics of atmosphere and solar radiation. Results show that the proposed network has the capacity to accurately provide atmospheric characteristics and estimate precise reflectivity spectra with 95,72% averaged accuracy for different materials, including vegetation, sea ice, and ocean. Additional experiments are designed to investigate the network’s temporal dependency and performance on missing data. The error analysis confirms that our proposed network is capable of estimating atmospheric characteristics under both seasonally and diurnally varying environments and handling the influence of missing data. Both the predicted results and error analysis are promising and demonstrate that our network has the ability of providing accurate atmospheric correction and target detection in real time. Numéro de notice : A2021-208 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2021.02.007 date de publication en ligne : 24/02/2021 En ligne : https://doi.org/10.1016/j.isprsjprs.2021.02.007 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97186 [article]

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POD of small LEO satellites based on precise real-time MADOCA and SBAS-aided PPP corrections / Amir Allahvirdi-Zadeh in GPS solutions, vol 25 n° 2 (April 2021)  

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Determination of the lunar body tide from global laser altimetry data / Robin N. Thor in Journal of geodesy, vol 95 n° 1 (January 2021)  

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Projet ROYMAGE : une horloge optique transportable pour des applications géodésiques et géophysiques [diaporama] / Guillaume Lion (2021) 

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ROYMAGE Project: a transportable clock for geodetic and geophysical applications / Guillaume Lion (2021) 

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SBAS-aided GPS positioning with an extended ionosphere map at the boundaries of WAAS service area / Mingyu Kim in Remote sensing, vol 13 n° 1 (January 2021)  

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Reference system origin and scale realization within the future GNSS constellation “Kepler” / Susanne Glaser in Journal of geodesy, vol 94 n° 12 (December 2020)  

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Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground networks / Wen Huang in Journal of geodesy, vol 94 n° 10 (October 2020)  

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Network-constrained bivariate clustering method for detecting urban black holes and volcanoes / Qiliang Liu in International journal of geographical information science IJGIS, vol 34 n° 10 (October 2020)  

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Crater detection and registration of planetary images through marked point processes, multiscale decomposition, and region-based analysis / David Solarna in IEEE Transactions on geoscience and remote sensing, vol 58 n° 9 (September 2020)  

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Novel communication channel model for signal propagation and loss through layered earth / David O. LeVan in IEEE Transactions on geoscience and remote sensing, vol 58 n° 8 (August 2020)  

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