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The triangulated affine transformation parameters and barycentric coordinates of Turkish Permanent GPS Network / Kutubuddin Ansari in Survey review, vol 50 n° 362 (August 2018)
Titre : The triangulated affine transformation parameters and barycentric coordinates of Turkish Permanent GPS Network Type de document : Article/Communication Auteurs : Kutubuddin Ansari, Auteur ; Ozsen Corumluoglu, Auteur ; Payal Verma, Auteur Année de publication : 2018 Article en page(s) : pp 412 - 415 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] barycentre
[Termes IGN] Eurasia Fixed Reference Frame
[Termes IGN] réseau géodésique permanent
[Termes IGN] transformation affine
[Termes IGN] transformation de coordonnées
[Termes IGN] TurquieRésumé : (Auteur) There are several computational approaches and methods to produce the complete solutions of geometry problems and they give sufficient computational strength for geodetic networks. Every approach and method has their advantages and drawbacks. Barycentric coordinates, also called areal coordinates, provide a new knock approach for geometry problems of such networks. This coordinate system offers triangular finite elements which are quite different from the usual Cartesian coordinate system. Actually, barycentric coordinates are a natural system of coordinates for the affine geometry. The modified approach for the affine transformation and barycentric coordinate system has been introduced and discussed, respectively in the study whether the affine transformation improves the results deteriorated by geometry of a GPS network. For this aim, general affine transformation of six-parameters between Eurasia Fixed Reference Frame (EUREF) and International Terrestrial Reference Frame (ITRF) for Turkish Permanent Global Positioning System Network (TPGN) has been computed. The affine transformation results show that the effects of the first and second translation parameters are in negative and positive directions, respectively. The third and sixth parameters are almost constant, on the other hand the fourth and fifth have a very small positive effect. Additionally, three triangular networks of GPS stations, at different locations in Turkey as a numerical example of barycentric coordinates, have also been presented. In the numerical example, the coordinate values of EUREF and ITRF have some differences after the decimal point, but the barycentric coordinates have very small amount of differences (sixth digit after decimal) which proves that the modified approach is meaningful. Numéro de notice : A2018-447 Affiliation des auteurs : non IGN Thématique : INFORMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2017.1297016 Date de publication en ligne : 05/03/2017 En ligne : https://doi.org/10.1080/00396265.2017.1297016 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91032
in Survey review > vol 50 n° 362 (August 2018) . - pp 412 - 415[article]
Titre : Barycentre method for solving distance equations Type de document : Article/Communication Auteurs : X. Shuqiang, Auteur ; Y. Yuanxi, Auteur ; D. Yamin, Auteur Année de publication : 2016 Article en page(s) : pp 188 - 194 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Mathématique
[Termes IGN] algorithme de Gauss-Newton
[Termes IGN] barycentre
[Termes IGN] distance
[Termes IGN] équation
[Termes IGN] itération
[Termes IGN] méthode des moindres carrésRésumé : (auteur) When iteratively solving the distance equations, the Newton’s method has quadratic convergence but it requires the second-order derivatives. The Gauss–Newton’s method needs no information about the second-order derivatives but it may fail without the line search strategy. A simple method called barycentre method is proposed to locally solving the distance equations without the Hessian matrix, the matrix inversion and the line search strategy. The geometrical meaning of the non-linear least-squares solution of the distance equations is revealed that it is the barycentre of a particle system composed of the observational weights at the endpoints of observed distance vectors. By the geometrical meaning of the non-linear least squares, the authors structure an iterative equation to solve the distance equation, and then the convergence and the computational complexity of the method proposed is discussed. It shows that the barycentre method is a conservatively steepest decent method to guarantee the convergence and this method has good performances for solving well-conditioned problems. Ultimately, the method proposed is applied to well-condition and ill-posed positioning equations and the main results are verified. Numéro de notice : A2016-275 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000020 En ligne : http://doi.org/10.1179/1752270615Y.0000000020 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80824
in Survey review > vol 48 n° 348 (May 2016) . - pp 188 - 194[article]
Titre : The choice of reference system in ITRF formulation Type de document : Article/Communication Auteurs : Zuheir Altamimi Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2012 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 137 Conférence : IAG 2009, 7th Hotine-Marussi Symposium on Mathematical Geodesy 06/06/2009 10/06/2009 Rome Italie Proceedings Springer Importance : pp 329 - 334 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] barycentre
[Termes IGN] coordonnées cartésiennes géocentriques
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] moment cinétique
[Termes IGN] système de référence géodésique
[Termes IGN] vitesseRésumé : (auteur) The problem of choosing an optimal reference system for the International Terrestrial Reference Frame (ITRF) is studied for both the rigorous solution which is a simultaneous stacking (removal of the reference system at each data epoch and implementation of a linear in time coordinate model) for all techniques, as well as for the usual numerically convenient separation into a set of individual stackings one for each technique and a final combination step for the derived initial coordinates and velocities. Two approaches are followed, an algebraic and a kinematic one. The algebraic approach implements the inner constraints, which minimize the sum of squares of the unknown parameters, as well as partial inner constraints, which minimize the sum of squares of a subset of the unknown parameters. In the kinematical approach the optimal minimal constraints are derived by requiring the minimization of the apparent coordinate variations: (a) with respect to the origin by imposing constant coordinates for the network barycenter, (b) with respect to orientation by imposing zero relative angular momentum for the network points conceived as mass points with equal mass and (c) with respect to the scale by imposing constant mean quadratic size (involving the distances of stations from their barycenter). Numéro de notice : C2009-036 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-22078-4_49 Date de publication en ligne : 18/10/2011 En ligne : https://doi.org/10.1007/978-3-642-22078-4_49 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91643
Titre : PostGIS pour les néophytes (4ème partie) Type de document : Article/Communication Auteurs : Anonyme, Auteur Année de publication : 2011 Article en page(s) : pp 40 - 45 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique
[Termes IGN] barycentre
[Termes IGN] centroïde
[Termes IGN] ellipsoïde de référence
[Termes IGN] mesurage de distances
[Termes IGN] opérateur spatial
[Termes IGN] PostGIS
[Termes IGN] primitive géométrique
[Termes IGN] projection
[Termes IGN] système de référence géodésiqueRésumé : (Auteur) Nous continuons notre découverte des principaux opérateurs spatiaux de PostGIS, avec, ce mois-ci, quelques fonctions moins communes. Nous abordons aussi les primitives géodésiques : définition des systèmes de référence, reprojections et mesures de longueur ellipsoïdales vraies. Numéro de notice : A2011-194 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30972
in Géomatique expert > n° 80 (01/05/2011) . - pp 40 - 45[article]Exemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 265-2011031 RAB Revue Centre de documentation En réserve L003 Disponible IFN-001-P001257 PER Revue Nogent-sur-Vernisson Salle périodiques Exclu du prêt 
contenu dans Proceedings Silvilaser 2010, The 10th International Conference on LiDAR Applications for Assessing Forest Ecosystems, September 14th - 17th, 2010 Freiburg, Germany / Barbara Koch (2010)
Titre : 3D segmentation of forest structure using an adaptive mean shift based procedure Type de document : Article/Communication Auteurs : António Ferraz Editeur : Fribourg [Allemagne] : University of Freiburg Année de publication : 2010 Conférence : SilviLaser 2010, 10th International Conference on LiDAR Applications for Assessing Forest Ecosystems 14/09/2010 17/09/2010 Fribourg Allemagne Proceedings Springer Importance : pp 281 - 291 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] algorithme de décalage moyen
[Termes IGN] barycentre
[Termes IGN] données lidar
[Termes IGN] données localisées 3D
[Termes IGN] Eucalyptus globulus
[Termes IGN] Pinus pinaster
[Termes IGN] Portugal
[Termes IGN] semis de points
[Termes IGN] strate végétaleRésumé : (auteur) Plant communities display a vertical structure based on the size and growth pattern of the dominant species. To a large extent, this pattern, called vertical stratification, depends on the climatic zone. Vertical structure analysis consists in detecting the number of layers and their limits within a forest stand. So far, there is a lack of robust approaches applied to airborne laser scanning (ALS) data that properly segment the different strata of forests having complex structures. In this study, we propose a procedure to characterize vertical forest stratification based on the mean shift (MS) algorithm. The MS is a non-linear filter that searches for local density maxima (modes). It is a non-parametric and unsupervised approach, which only requires a single criterion, the kernel bandwidth. Since the forest point cloud is a multi-modal distribution, the MS is used to find the modes which are supposed to be the barycenters of vegetation features. Once achieved, the modes are grouped together according to height range and the corresponding ALS points are assigned to each vegetation strata. Due to their complex pattern, using a single scale over the whole space is not recommended for the analysis of such environments. On this basis, the modes are computed using a variable kernel bandwidth according to the forest pattern. To depict such a pattern, we propose a new technique that segments the main forest layers at the plot level: overstory, understory, and surface vegetation. The procedure has been carried out on 45 plots of a Portuguese forest mainly composed of eucalyptus (Eucalyptus globulus) and pine (Pinus pinaster) trees that can be strongly populated by understory and surface vegetation. Numéro de notice : C2010-020 Affiliation des auteurs : MATIS+Ext (1993-2011) Thématique : FORET/IMAGERIE Nature : Communication DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83729 Documents numériques
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