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Design and performance evaluation of a novel ranging signal based on an LEO satellite communication constellation / Jingfang Su in Geo-spatial Information Science, vol 26 n° 1 (March 2023)
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Titre : Design and performance evaluation of a novel ranging signal based on an LEO satellite communication constellation Type de document : Article/Communication Auteurs : Jingfang Su, Auteur ; Jia Su, Auteur ; Qingwu Yi, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : pp 107 - 124 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal
[Termes IGN] bruit blanc
[Termes IGN] orbite basse
[Termes IGN] rapport signal sur bruit
[Termes IGN] transformation de Fourier
[Termes IGN] transformation inverseRésumé : (auteur) Driven by improvements in satellite internet and Low Earth Orbit (LEO) navigation augmentation, the integration of communication and navigation has become increasingly common, and further improving navigation capabilities based on communication constellations has become a significant challenge. In the context of the existing Orthogonal Frequency Division Multiplexing (OFDM) communication systems, this paper proposes a new ranging signal design method based on an LEO satellite communication constellation. The LEO Satellite Communication Constellation Block-type Pilot (LSCC-BPR) signal is superimposed on the communication signal in a block-type form and occupies some of the subcarriers of the OFDM signal for transmission, thus ensuring the continuity of the ranging pilot signal in the time and frequency domains. Joint estimation in the time and frequency domains is performed to obtain the relevant distance value, and the ranging accuracy and communication resource utilization rate are determined. To characterize the ranging performance, the Root Mean Square Error (RMSE) is selected as an evaluation criterion. Simulations show that when the number of pilots is 2048 and the Signal-to-Noise Ratio (SNR) is 0 dB, the ranging accuracy can reach 0.8 m, and the pilot occupies only 50% of the communication subcarriers, thus improving the utilization of communication resources and meeting the public demand for communication and location services. Numéro de notice : A2023-209 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/10095020.2022.2121229 Date de publication en ligne : 17/11/2022 En ligne : https://doi.org/10.1080/10095020.2022.2121229 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103136
in Geo-spatial Information Science > vol 26 n° 1 (March 2023) . - pp 107 - 124[article]Optimising 2-parameter Lambert Conformal Conic projections for ground-to-grid distortions / Sergio Baselga in Survey review, Vol 53 n° 380 (September 2021)
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Titre : Optimising 2-parameter Lambert Conformal Conic projections for ground-to-grid distortions Type de document : Article/Communication Auteurs : Sergio Baselga, Auteur Année de publication : 2021 Article en page(s) : pp 415 - 421 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Projections
[Termes IGN] carroyage géographique
[Termes IGN] déformation géométrique
[Termes IGN] projection conique de Lambert
[Termes IGN] projection Universal Transverse Mercator
[Termes IGN] transformation inverseRésumé : (auteur) A Lambert Conformal Conic (LCC) projection with two true-scale parallels of latitudes ϕl and ϕu can be recast in a LCC projection with one standard parallel of latitude ϕ0 and scale k0, having the practical advantage that the same type of definition can be used for the two conformal projections universally used: LCC and Transverse Mercator (TM). While equations giving ϕ0 and k0 in terms ϕl and ϕu can be found in the literature, inverse relationships are not readily found. They are derived in the present paper. These may be necessary in views of the planned future definition of the United States State Plane Coordinate System (SPCS) 2022 for the users of particular mapping software requiring to specify the two latitude values instead of the central latitude and central scale. While map projection parameters are customary selected to minimise ellipsoid-to-grid distortions for a region, in some cases it could be more convenient to study and minimise ground-to-grid distortions. Also bearing in mind the design of SPCS 2022, we discuss the advantages and disadvantages of working with each type of distortion definition. Numéro de notice : A2021-638 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2020.1797339 Date de publication en ligne : 28/07/2020 En ligne : https://doi.org/10.1080/00396265.2020.1797339 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98305
in Survey review > Vol 53 n° 380 (September 2021) . - pp 415 - 421[article]
Titre : Analyzing and improving Graph Neural Networks Type de document : Thèse/HDR Auteurs : Guillaume Renton, Auteur ; Sébastien Adam, Auteur Editeur : Université de Rouen Année de publication : 2021 Importance : 130 p. Format : 21 x 30 cm Note générale : bibliographie
Thèse présentée pour obtenir le diplôme de Doctorat de l'Université de Rouen Normandie, spécialité InformatiqueLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Intelligence artificielle
[Termes IGN] apprentissage profond
[Termes IGN] classification par réseau neuronal convolutif
[Termes IGN] filtre passe-bande
[Termes IGN] filtre spectral
[Termes IGN] noeud
[Termes IGN] réseau neuronal de graphes
[Termes IGN] théorie des graphes
[Termes IGN] transformation de Laplace
[Termes IGN] transformation inverseIndex. décimale : THESE Thèses et HDR Résumé : (auteur) Although theorised about fifteen years ago, the scientific community’s interest for graph neural networks has only really taken off recently. Those models aim to transpose the representation learning capacity inherent in deep neural network onto graph data, via the learning of hidden states associated with the graph nodes. These hidden states are computed and updated according to the information contained in the neighborhoud of each node.This recent interest for graph neural networks (GNNs) has led to a "jungle" of models and frameworks, making this field of research sometimes confusing. Historically, two main strategies have been explored : the spatial GNNs on one side and the spectral GNNs on the other side. Spatial GNNs, sometimes also called Message Passing Neural Network, are based on the computation of a message which agregates the information contained in the neighborhoud of each node. On the other side, spectral GNNs are based on the spectral graph theory and thus on the graph Laplacian. The eigendecomposition of the graph Laplacian allows to define a graph Fourier transform and its inverse. From these transforms, different filters can be applied on the graph, leading to similar result than filtering on images or signals. In this thesis, we begin by introducing a third category, called spectral rooted spatial convolution. Indeed, some recent methods are taking root in the spectral domain while avoiding to compute the eigendecomposition of the graph Laplacian. This third category leads to question about the fundamental difference between spectral and spatial GNNs. We answer this question by proposing a general model unifying both strategies, showing notably that spectral GNNs are a particular case of spatial GNNs. This unified model also allowed us to propose a spectral analysis of some popular GNNs in the scientificcommunitic, namely GCN, GIN, GAT, ChebNet and CayleyNet. This analysis shows that spatial models are limited to low-pass and high-pass filtering, while spectral models can produce any kind of filters. Those results are then found with the presentation of a toy problem, showing in the first instance the limitation of spatial models to define pass-band filters, and the importance of designing such filters. Those results have led us to propose a method allowing any kind of filter, while limiting the network’s number of parameters. Indeed, even though spectral models are able to design any kind of filtering, each new filter require the add of a new weight matrix in the neural network. In order to reduce the number of parameters, we propose to adapt Depthwise Separable Convolution to graphs through a method called Depthwise Separable Graph Convolution Network. This method is evaluated on both transductive and inductive learning, outperforming state-of-the-arts results.Finally, we propose a method defined in the spatial domain in order to take into account edge attributes. Indeed, this issue has been little studied by the scientific community, and the number of methods allowing to include edge attributes is very small. Our proposal, called Edge Embedding Graph Neural Network, consists in embedding edge attributes into a new space through a first neural network, before using the extracted features in a GNN. This method is evaluated on a particular problem of symbol detection in a graph. Note de contenu : 1- Introduction
2- Background
3- What is a Graph Neural Network ?
4- Graph Neural Networks: Are they Spectral or Spatial ?
5- Depthwise Separable Graph Convolution Network
6- Edge Embedding Graph Neural Network
7- ConclusionNuméro de notice : 15259 Affiliation des auteurs : non IGN Thématique : INFORMATIQUE/MATHEMATIQUE Nature : Thèse française Note de thèse : Thèse de Doctorat : Informatique : Rouen : 2021 Organisme de stage : Laboratoire LITIS DOI : sans En ligne : https://tel.hal.science/tel-03346018/ Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100612 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)
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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 IGN] harmonique sphérique
[Termes IGN] série de Fourier
[Termes IGN] transformation géométrique
[Termes IGN] transformation inverseRésumé : (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 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1049-3 Date de publication en ligne : 13/07/2017 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
in Journal of geodesy > vol 92 n° 2 (February 2018) . - pp 123 - 130[article]L'établissement et l'emploi d'une table pour la transformation des coordonnées géographiques et coordonnées rectangulaires et pour la transformation inverse / Henri Roussilhe (1927)
Titre : L'établissement et l'emploi d'une table pour la transformation des coordonnées géographiques et coordonnées rectangulaires et pour la transformation inverse Type de document : Article/Communication Auteurs : Henri Roussilhe, Auteur Editeur : Paris : Imprimerie Hallu Année de publication : 1927 Conférence : IUGG 1927, 3rd general assembly, UGGI 3e conférence générale 29/08/1927 10/09/1927 Prague Tchécoslovaquie Importance : 28 p. Format : 21 x 27 cm Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie ancienne
[Termes IGN] coordonnées géographiques
[Termes IGN] coordonnées rectangulaires
[Termes IGN] ellipsoïde (géodésie)
[Termes IGN] géophysique
[Termes IGN] transformation inverseNuméro de notice : 25499 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Communication Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94334 Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 25499-01 CG1927 Livre Centre de documentation En réserve M-103 Fonds ancien - consultable sur RdV
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