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Fast calculation of gravitational effects using tesseroids with a polynomial density of arbitrary degree in depth / Fang Ouyang in Journal of geodesy, vol 96 n° 12 (December 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 12 (December 2022) . - n° 97 Titre : Fast calculation of gravitational effects using tesseroids with a polynomial density of arbitrary degree in depth Type de document : Article/Communication Auteurs : Fang Ouyang, Auteur ; Long-wei Chen, Auteur ; Zhi-gang Shao, Auteur Année de publication : 2022 Article en page(s) : n° 97 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de gravitation [Termes IGN] coordonnées sphériques [Termes IGN] discrétisation [Termes IGN] intégrale de Newton [Termes IGN] inversion [Termes IGN] quadrature [Termes IGN] tesseroid [Termes IGN] transformation rapide de Fourier Résumé : (auteur) Fast and accurate calculation of gravitational effects on a regional or global scale with complex density environment is a critical issue in gravitational forward modelling. Most existing significant developments with tessroid-based modelling are limited to homogeneous density models or polynomial ones of a limited order. Moreover, the total gravitational effects of tesseroids are often calculated by pure summation in these methods, which makes the calculation extremely time-consuming. A new efficient and accurate method based on tesseroids with a polynomial density up to an arbitrary order in depth is developed for 3D large-scale gravitational forward modelling. The method divides the source region into a number of tesseroids, and the density in each tesseroid is assumed to be a polynomial function of arbitrary degree. To guarantee the computational accuracy and efficiency, two key points are involved: (1) the volume Newton’s integral is decomposed into a one-dimensional integral with a polynomial density in the radial direction, for which a simple analytical recursive formula is derived for efficient calculation, and a surface integral over the horizontal directions evaluated by the Gauss–Legendre quadrature (GLQ) combined with a 2D adaptive discretization strategy; (2) a fast and flexible discrete convolution algorithm based on 1D fast Fourier transform (FFT) and a general Toepritz form of weight coefficient matrices is adopted in the longitudinal dimension to speed up the computation of the cumulative contributions from all tesseroids. Numerical examples show that the gravitational fields predicted by the new method have a good agreement with the corresponding analytical solutions for spherical shell models with both polynomial and non-polynomial density variations in depth. Compared with the 3D GLQ methods, the new algorithm is computationally more accurate and efficient. The calculation time is significantly reduced by 3 orders of magnitude as compared with the traditional 3D GLQ methods. Application of the new algorithm in the global crustal CRUST1.0 model further verifies its reliability and practicability in real cases. The proposed method will provide a powerful numerical tool for large-scale gravity modelling and also an efficient forward engine for inversion and continuation problems. Numéro de notice : A2022-896 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s00190-022-01688-9 Date de publication en ligne : 05/12/2022 En ligne : https://doi.org/10.1007/s00190-022-01688-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102248 [article]

Spherically optimized RANSAC aided by an IMU for Fisheye Image Matching / Anbang Liang in Remote sensing, vol 13 n°10 (May-2 2021)  

Public [article]  inRemote sensing > vol 13 n°10 (May-2 2021) . - n° 2017 Titre : Spherically optimized RANSAC aided by an IMU for Fisheye Image Matching Type de document : Article/Communication Auteurs : Anbang Liang, Auteur ; Qingquan Li, Auteur ; Zhipeng Chen, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] appariement d'images [Termes IGN] centrale inertielle [Termes IGN] coordonnées sphériques [Termes IGN] distorsion d'image [Termes IGN] estimation de pose [Termes IGN] étalonnage de chambre métrique [Termes IGN] géométrie épipolaire [Termes IGN] image hémisphérique [Termes IGN] Ransac (algorithme) Résumé : (auteur) Fisheye cameras are widely used in visual localization due to the advantage of the wide field of view. However, the severe distortion in fisheye images lead to feature matching difficulties. This paper proposes an IMU-assisted fisheye image matching method called spherically optimized random sample consensus (So-RANSAC). We converted the putative correspondences into fisheye spherical coordinates and then used an inertial measurement unit (IMU) to provide relative rotation angles to assist fisheye image epipolar constraints and improve the accuracy of pose estimation and mismatch removal. To verify the performance of So-RANSAC, experiments were performed on fisheye images of urban drainage pipes and public data sets. The experimental results showed that So-RANSAC can effectively improve the mismatch removal accuracy, and its performance was superior to the commonly used fisheye image matching methods in various experimental scenarios. Numéro de notice : A2021-416 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.3390/rs13102017 Date de publication en ligne : 20/05/2021 En ligne : https://doi.org/10.3390/rs13102017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97757 [article]

Weighted spherical sampling of point clouds for forested scenes / Alex Fafard in Photogrammetric Engineering & Remote Sensing, PERS, vol 86 n° 10 (October 2020)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 86 n° 10 (October 2020) . - pp 619 - 625 Titre : Weighted spherical sampling of point clouds for forested scenes Type de document : Article/Communication Auteurs : Alex Fafard, Auteur ; Ali Rouzbeh Kargar, Auteur ; Jan Van Aardt, Auteur Année de publication : 2020 Article en page(s) : pp 619 - 625 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] coordonnées sphériques [Termes IGN] densité de la végétation [Termes IGN] diamètre à hauteur de poitrine [Termes IGN] données lidar [Termes IGN] échantillonnage [Termes IGN] mangrove [Termes IGN] Micronésie [Termes IGN] scène forestière [Termes IGN] semis de points [Termes IGN] volume en bois Résumé : (Auteur) Terrestrial laser scanning systems are characterized by a sampling pattern which varies in point density across the hemisphere. Additionally, close objects are over-sampled relative to objects that are farther away. These two effects compound to potentially bias the three-dimensional statistics of measured scenes. Previous methods of sampling have resulted in a loss of structural coherence. In this article, a method of sampling is proposed to optimally sample points while preserving the structure of a scene. Points are sampled along a spherical coordinate system, with probabilities modulated by elevation angle and squared distance from the origin. The proposed approach is validated through visual comparison and stem-volume assessment in a challenging mangrove forest in Micronesia. Compared to several well-known sampling techniques, the proposed approach reduces sampling bias and shows strong performance in stem-reconstruction measurement. The proposed sampling method matched or exceeded the stem-volume measurement accuracy across a variety of tested decimation levels. On average it achieved 3.0% higher accuracy at estimating stem volume than the closest competitor. This approach shows promise for improving the evaluation of terrestrial laser-scanning data in complex scenes. Numéro de notice : A2020-493 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.14358/PERS.86.10.619 Date de publication en ligne : 01/10/2020 En ligne : https://doi.org/10.14358/PERS.86.10.619 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96093 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
105-2020101	SL	Revue	Centre de documentation	Revues en salle	Disponible

Optimized formulas for the gravitational field of a tesseroid / Thomas Grombein in Journal of geodesy, vol 87 n° 7 (July 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 7 (July 2013) . - pp 645 - 660 Titre : Optimized formulas for the gravitational field of a tesseroid Type de document : Article/Communication Auteurs : Thomas Grombein, Auteur ; Kurt Seitz, Auteur ; Bernard Heck, Auteur Année de publication : 2013 Article en page(s) : pp 645 - 660 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] coordonnées cartésiennes géocentriques [Termes IGN] coordonnées sphériques [Termes IGN] intégrale de Newton [Termes IGN] tesseroid Résumé : (Auteur) Various tasks in geodesy, geophysics, and related geosciences require precise information on the impact of mass distributions on gravity field-related quantities, such as the gravitational potential and its partial derivatives. Using forward modeling based on Newton’s integral, mass distributions are generally decomposed into regular elementary bodies. In classical approaches, prisms or point mass approximations are mostly utilized. Considering the effect of the sphericity of the Earth, alternative mass modeling methods based on tesseroid bodies (spherical prisms) should be taken into account, particularly in regional and global applications. Expressions for the gravitational field of a point mass are relatively simple when formulated in Cartesian coordinates. In the case of integrating over a tesseroid volume bounded by geocentric spherical coordinates, it will be shown that it is also beneficial to represent the integral kernel in terms of Cartesian coordinates. This considerably simplifies the determination of the tesseroid’s potential derivatives in comparison with previously published methodologies that make use of integral kernels expressed in spherical coordinates. Based on this idea, optimized formulas for the gravitational potential of a homogeneous tesseroid and its derivatives up to second-order are elaborated in this paper. These new formulas do not suffer from the polar singularity of the spherical coordinate system and can, therefore, be evaluated for any position on the globe. Since integrals over tesseroid volumes cannot be solved analytically, the numerical evaluation is achieved by means of expanding the integral kernel in a Taylor series with fourth-order error in the spatial coordinates of the integration point. As the structure of the Cartesian integral kernel is substantially simplified, Taylor coefficients can be represented in a compact and computationally attractive form. Thus, the use of the optimized tesseroid formulas particularly benefits from a significant decrease in computation time by about 45 % compared to previously used algorithms. In order to show the computational efficiency and to validate the mathematical derivations, the new tesseroid formulas are applied to two realistic numerical experiments and are compared to previously published tesseroid methods and the conventional prism approach. Numéro de notice : A2013-399 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0636-1 Date de publication en ligne : 18/05/2013 En ligne : https://doi.org/10.1007/s00190-013-0636-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32537 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013071	SL	Revue	Centre de documentation	Revues en salle	Disponible

Introduction à l’astronomie de position / Jonathan Chenal (2012)

Public Titre : Introduction à l’astronomie de position : Leçon aux élèves du Mastère de Photogrammétrie, Positionnement et Mesures de Déformations, Option Géodésie le 13 février 2012 à Marne-la-Vallée Type de document : Guide/Manuel Auteurs : Jonathan Chenal , Auteur Editeur : Paris : Institut Géographique National - IGN (1940-2007) Année de publication : 2012 Importance : 227 p. Format : 21 x 30 cm Note générale : Bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Astronomie fondamentale [Termes IGN] coordonnées sphériques [Termes IGN] détermination astronomique [Termes IGN] échelle de temps [Termes IGN] force de gravitation [Termes IGN] International Terrestrial Reference Frame [Termes IGN] Lune [Termes IGN] mouvement du pôle [Termes IGN] nutation [Termes IGN] précession [Termes IGN] repère de référence céleste [Termes IGN] rotation de la Terre [Termes IGN] système international de référence céleste [Termes IGN] système solaire [Termes IGN] Terre (planète) [Termes IGN] triangle de position [Termes IGN] trigonométrie sphérique Note de contenu : Introduction 1 L'astronomie : l'Homme dans l'Univers 1.1 L'Univers 1.2 La Voie Lactée, une galaxie parmi d'autres 1.3 Le système solaire 1.4 La Terre 2 Les mouvements de la Terre, approche physique 2.1 Un seul moteur, la gravitation 2.2 La révolution autour du Soleil 2.3 Le problème de la Lune 2.4 La rotation diurne 2.5 La précession 2.6 La nutation 2.7 Le mouvement du pôle 2.8 Conséquences visibles des mouvements de la Terre 3 Les échelles de temps 3.1 Définitions 3.2 Les calendriers 3.3 Les échelles de temps scientifiques 4 Les repères spatiaux utilisés en astronomie 4.1 Les systèmes de coordonnées sphériques 4.2 Les repères de référence célestes 4.3 Le repère international de référence terrestre 4.4 L'approche classique de la transformation du repère terrestre au repère céleste 5 L'utilité des astres et de l'astronomie de position 5.1 Trigonométrie sphérique 5.3 L'utilisation d'éphémérides 5.4 La détermination de l'heure 5.5 La détermination de la position 5.6 La détermination d'un azimut par observation du Soleil Conclusion Numéro de notice : 14448 Affiliation des auteurs : IGN (2012-2019) Thématique : POSITIONNEMENT Nature : Manuel de cours IGN nature-HAL : Cours DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=46393

Introduction à l’astronomie de position / Jonathan Chenal (2011)

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Projecting global datasets to achieve equal areas / E. Lynn Usery in Cartography and Geographic Information Science, vol 30 n° 1 (January 2003)  

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Die Gaussschen und geographischen Koordinaten auf dem Ellipsoid von Krassowsky / W.K. Hristow (1955)

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Jordan - Eggert - Handbuch der Vermessungskunde, 3. Dritter Band, zweiter Halbband / W. Jordan (1948)

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Lehrbuch der Astronomie und der mathematischen Geographie. 1. Teil Sphärische Astronomie / W. Laska (1906)

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Jordan - Handbuch der Vermessungskunde, Band 2. Höhere Geodäsie / W. Jordan (1878)

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