Centre dedocumentation
scientifique

Shadow detection and removal in RGB VHR images for land use unsupervised classification / A. Movia in ISPRS Journal of photogrammetry and remote sensing, vol 119 (September 2016)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 119 (September 2016) . - pp 485 - 495 Titre : Shadow detection and removal in RGB VHR images for land use unsupervised classification Type de document : Article/Communication Auteurs : A. Movia, Auteur ; A. Beina, Auteur ; F. Crosilla, Auteur Année de publication : 2016 Article en page(s) : pp 485 - 495 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] analyse comparative [Termes IGN] analyse d'image numérique [Termes IGN] analyse procustéenne [Termes IGN] anisotropie [Termes IGN] classification non dirigée [Termes IGN] détection d'ombre [Termes IGN] détection de changement [Termes IGN] factorisation de Cholesky [Termes IGN] image à très haute résolution [Termes IGN] image RVB Résumé : (Auteur) Nowadays, high resolution aerial images are widely available thanks to the diffusion of advanced technologies such as UAVs (Unmanned Aerial Vehicles) and new satellite missions. Although these developments offer new opportunities for accurate land use analysis and change detection, cloud and terrain shadows actually limit benefits and possibilities of modern sensors. Focusing on the problem of shadow detection and removal in VHR color images, the paper proposes new solutions and analyses how they can enhance common unsupervised classification procedures for identifying land use classes related to the CO2 absorption. To this aim, an improved fully automatic procedure has been developed for detecting image shadows using exclusively RGB color information, and avoiding user interaction. Results show a significant accuracy enhancement with respect to similar methods using RGB based indexes. Furthermore, novel solutions derived from Procrustes analysis have been applied to remove shadows and restore brightness in the images. In particular, two methods implementing the so called “anisotropic Procrustes” and the “not-centered oblique Procrustes” algorithms have been developed and compared with the linear correlation correction method based on the Cholesky decomposition. To assess how shadow removal can enhance unsupervised classifications, results obtained with classical methods such as k-means, maximum likelihood, and self-organizing maps, have been compared to each other and with a supervised clustering procedure. Numéro de notice : A2016-793 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern En ligne : http://dx.doi.org/10.1016/j.isprsjprs.2016.05.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82510 [article]

Regional gravity field modelling with radial basis functions / Tobias Wittwer (2009)  

Public Titre : Regional gravity field modelling with radial basis functions Type de document : Thèse/HDR Auteurs : Tobias Wittwer, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2009 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 72 Importance : 190 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-315-0 Note générale : Bibliographie Document téléchargeable sur le site de NCG : voir lien dans la notice Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Antarctique [Termes IGN] Canada [Termes IGN] champ de pesanteur local [Termes IGN] données GOCE [Termes IGN] données GRACE [Termes IGN] factorisation de Cholesky [Termes IGN] filtre de Wiener [Termes IGN] fonction de base radiale [Termes IGN] Groenland [Termes IGN] harmonique sphérique [Termes IGN] levé gravimétrique [Termes IGN] modèle de géopotentiel [Termes IGN] modèle mathématique Résumé : (Auteur) Terrestrial gravimetry, airborne gravimetry, and the recent dedicated satellite gravity missions Challenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity and Ocean Circulation Explorer (GOCE) provide us with high-quality, high-resolution gravity data, which are used in many application areas such as 1. the computation of global static gravity fields, in support of precise orbit determination of many Earth observation satellites; 2. the quantification and interpretation of mass transport in the Earth system such as the shrinking of ice sheets, the shifting of ocean currents, and water storage variations; 3. the computation of high resolution regional and local gravity fields in support of height system realisation and the modelling of reservoirs and geophysical features. Traditionally, for each data set (satellite, airborne, terrestrial) dedicated data processing schemes have been developed using different estimation principles, parametrisations, etc. The optimal combination of different data sets would benefit of a methodology that can be used for any type of data. Elements of this methodology comprise a uniform parametrisation, estimation principle, data weighting scheme, regularisation, and error propagation. In the framework of this thesis, such a methodology is developed. It uses radial basis functions (RBFs) as parametrisation. They have parameters that allow us to tune their approximation properties as function of the data coverage and distribution and the signal variations. This makes them equally well suited for global and local parametrisation. Moreover, there exists an analytical relationship between a spherical harmonic representation and a radial basis function representation, which allows the latter to be transformed into the former, without any approximation error. Among others, this has the advantage that one can make use of existing processing tools, such as spectral analysis. Although radial basis functions are not new in gravity field modelling, there are many important issues which have not yet been addressed or require further research. The main research question underlying this thesis is: "Are radial basis functions a suitable parametrisation for global and regional models of the mean and time-variable gravity field, and if so, how do they perform compared with spherical harmonic solutions?" Directly related to this is the question: "Are there situations where radial basis functions models outperform spherical harmonic solutions?" The answer to both questions is positive as will be shown in this thesis. There are two important aspects that determine the quality of a gravity field model based on radial basis functions: 1) the spatial distribution of the radial basis functions, i.e. the basis function network design, and 2) the choice of the bandwidths of the radial basis functions. For both problems, semi-automatic algorithms have been developed. Data-adaptive network design and local refinement avoid respectively over- and under-parametrisation by fine-tuning the basis function network based on the data. The basis function bandwidth is determined by optimising the fit to the data including control data. The computation of regional gravity fields constitutes a considerable numerical workload, especially since the methodology presented here does not use an iterative normal equation solver (e.g., the preconditioned conjugate gradient method). Instead, a Cholesky solver is used, which requires the assembly of the complete normal equation system. For this purpose the program is numerically optimised and fully parallelised for hybrid high performance computer architectures. This guarantees optimal performance on all types of parallel computers and handles the memory requirements. The modelling of satellite data with radial basis functions is investigated using real data of the GRACE satellites collected over the period 2003-2006. An optimal Wiener filter has been developed for radial basis functions in line with the optimal Wiener filter approach previously developed at DEOS for spherical harmonic representations. Monthly GRACE gravity models computed using radial basis function are compared to spherical harmonic models, and validated using independent data provided by the Ice Cloud and Land Elevation Satellite (ICESat), radar altimetry satellites, and the global hydrological model PCR-GLOBWB. Two applications were considered: 1) mass variations over Greenland and Antarctica and 2) water storage variations in river basins. The results show that the radial basis function approach yields solutions that are of at least the same quality as global models using spherical harmonics. There is evidence that radial basis functions may provide better spatial resolution and more realistic amplitudes in particular in high-latitude areas. For instance, it will be shown that radial basis function solutions detected signal that could not be seen in spherical harmonic solutions. Two test areas are used for regional gravity field modelling using real terrestrial data: An area in the northeastern USA and a larger area in eastern Canada. The results show that the data-adaptivity and local refinement algorithms developed in the framework of this thesis provide good solutions of constant quality regardless of the initially chosen grid spacing. The models are compared to the official regional geoid models GEOID03 and CGG05, respectively. In both cases, rms errors of several centimetres remain, which are attributed to different input data and processing strategies. The combination of satellite and terrestrial data is tested using simulated global and regional data sets. It is shown that a joint inversion of the two data sets yields combined solutions which are significantly better than a solution using the traditional remove-restore approach. The addition of satellite data with the corresponding stochastic model compensates the reduced quality of the terrestrial data at long wavelengths. The examples show that the regional modelling methodology presented here is a very flexible approach that can be applied to all types of gravity data and data distributions, regardless of application, data source, and area size. The quality of the solutions is at least equal to the solutions developed for the stand-alone inversion of individual data sets, while radial basis functions offer numerical benefits. As a result, this approach is already used for marine geoid modelling, and recommended for the modelling of airborne gravity data and data of the GOCE satellite, and for the joint inversion of satellite, airborne and ground-based gravity data. Note de contenu : Nomenclature 1 Introduction 1.1 Background 1.2 Motivation 1.2.1 Regional modelling from satellite data 1.2.2 Regional modelling from terrestrial data 1.2.3 Combined modelling of satellite and terrestrial data 1.2.4 Radial basis functions 1.3 Prior research on radial basis functions 1.4 Research objectives 1.5 Outline of thesis 2 Radial basis functions 2.1 Gravity field representations 2.1.1 Spherical harmonics 2.1.2 Radial basis functions 2.2 RBF types and behaviour in the spectral domain 2.3 Behaviour in the spatial domain 2.4 Relation of RBFs to a spherical harmonic representation 2.5 Choice of RBF characteristics 2.5.1 Choice of the kernel 2.5.2 Bandwidth selection 2.6 RBF network design 2.6.1 Grids 2.6.2 Adaptation to data 2.6.3 Local refinement 2.7 Multi-scale modelling 2.7.1 Introduction 2.7.2 Methodology 2.7.3 Filtering 3 Mathematical model and estimation principle 3.1 Functional model 3.2 Stochastic model 3.3 Least-squares estimation and regularisation 3.4 Solution strategies 3.4.1 Cholesky factorisation 3.4.2 Conjugate gradients 3.5 Variance component estimation . 3.5.1 Normal equations 3.5.2 Variance component estimation 3.5.3 Stochastic trace estimation 4 Numerical aspects 4.1 Numerical optimisation 4.1.1 Constant expressions in "do"-loops 4.1.2 Computation of the design matrix 4.1.3 Normalisation of coordinates 4.1.4 Normalisation of basis functions 4.2 Fast synthesis 4.3 Parallelisation 4.3.1 Problem description 4.3.2 Parallel computer architectures . 4.3.3 Parallelisation for shared memory computers 4.3.4 Parallelisation for distributed memory computers 4.3.5 Hybrid parallelisation 4.3.6 Results of parallelisation 4.4 Summary and conclusions 5 Gravity field modelling from satellite data 5.1 Functional model 5.1.1 Three-point range combination approach 5.1.2 Residual accelerations 5.1.3 Equivalent water heights 5.1.4 Trend and signal amplitude estimation 5.2 Stochastic model 5.3 Optimal filtering 5.3.1 Introduction 5.3.2 Signal covariance matrix computation 5.3.3 Noise level estimation 5.4 RBF network design 5.4.1 Grid choice 5.4.2 Data-adaptivity and local refinement 5.4.3 Parametrised area 5.5 Bandwidth selection 5.6 Results. 5.6.1 Comparison of unfiltered RBF and spherical harmonic solution 5.6.2 Models used for comparison 5.6.3 Recovery of ice mass loss in Greenland and Antarctica 5.6.4 Recovery of terrestrial water storage variations 5.7 Summary and conclusions 6 Local gravity field modelling from terrestrial data 6.1 Functional model 6.1.1 Functional model for gravity disturbances 6.1.2 Functional model for gravity anomalies 6.1.3 Functional model for height anomalies 6.2 RBF network design 6.2.1 Grid choice 6.2.2 Data-adaptivity and local refinement 6.2.3 Parametrised area 6.3 Bandwidth selection 6.4 Results 6.4.1 Northeastern USA 6.4.2 Canada 6.5 Summary and conclusions 7 Combined modelling of satellite and terrestrial data 7.1 Combination strategies 7.1.1 Remove-restore approach 7.1.2 High-pass filtering 7.1.3 Direct combination 7.1.4 Combination with satellite-only solution 7.2 RBF network design and bandwidth selection 7.3 Results 7.3.1 Global test 7.3.2 Regional test 7.4 Summary and conclusions 8 Summary, conclusions and recommendations 8.1 Summary and conclusions 8.2 Recommendations for further research Numéro de notice : 15511 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD thesis En ligne : https://www.ncgeo.nl/index.php/en/publicatiesgb/publications-on-geodesy/item/258 [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62744

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
15511-01	30.42	Livre	Centre de documentation	Géodésie	Disponible

A new method for three-carrier GNSS ambiguity resolution / U. Fernandez-Plazaola in Journal of geodesy, vol 82 n° 4-5 (April - May 2008)

Public [article]  inJournal of geodesy > vol 82 n° 4-5 (April - May 2008) . - pp 269 - 278 Titre : A new method for three-carrier GNSS ambiguity resolution Type de document : Article/Communication Auteurs : U. Fernandez-Plazaola, Auteur ; T. Martin-Guerrero, Auteur ; J. Entrambasaguas, Auteur Année de publication : 2008 Article en page(s) : pp 269 - 278 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] factorisation de Cholesky [Termes IGN] phase GPS [Termes IGN] résolution d'ambiguïté [Termes IGN] signal GNSS Résumé : (Auteur) A new method for resolving the carrier-phase integer ambiguity in Global Navigation Satellite Systems (GNSS) is presented: the MOdified Cholesky factorization for Ambiguity (MOCA) resolution. The characteristics and features of this method are described and results obtained using a software simulator and an emulator are presented to validate its efficiency. The results are then compared to those obtained using another existing method and good performance of the MOCA method in new GNSS systems is shown. Furthermore, the proposed method yields accurate results even when short time spans are used or when there are poor estimations of measurement error, making it immune to non-ideal conditions and ultimately a practical solution for real applications. Copyright Springer Numéro de notice : A2008-170 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29165 [article]

Réservation

Réserver ce document

Exemplaires (2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-08042	RAB	Revue	Centre de documentation	En réserve 3L	Disponible
266-08041	RAB	Revue	Centre de documentation	En réserve 3L	Disponible

Migration de CALTOPO, lissage de courbes de niveau / K.R. Kouadio (2003)

Public Titre : Migration de CALTOPO, lissage de courbes de niveau Type de document : Mémoire Auteurs : K.R. Kouadio, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2003 Importance : 53 p. Format : 21 x 30 cm Note générale : Bibliographie Rapport de projet, mastère de spécialisation en photogrammétrie numérique, image métrique, vision 3D Langues : Français (fre) Descripteur : [Vedettes matières IGN] Produits informatiques [Termes IGN] factorisation de Cholesky [Termes IGN] fonction spline [Termes IGN] isohypse [Termes IGN] lissage de courbe [Termes IGN] migration de logiciel [Termes IGN] modèle numérique de surface [Termes IGN] semis de points [Termes IGN] Visual C++ Index. décimale : MPPMD Mémoires du mastère spécialisé Photogrammétrie, Positionnement et Mesures de Déformation Résumé : (Auteur) Ce stage rentre dans le cadre de la formation pratique des étudiants du mastère de photogrammétrie numérique, image métrique - vision 3D. Il s'est déroulé dans les locaux de la Société Topographie Informatique sise à Evry. Ce stage s'est articulé autour de deux pôles, à savoir la migration du logiciel de calculs topographiques CALTOPO et le développement d'un module de densification de points afin de rendre les courbes de niveau résultantes plus lisses. La migration de CALTOPO a consister à créer un nouvel outil, dans un environnement nouveau. Ainsi, il passe d'un environnement MS-DOS à un environnement Windows. La nouvelle version est opérationnelle. Densifier un semi de points, par la création d'une surface paramétrée selon cet échantillon, est le principe retenu pour répondre au besoin de lissage des courbes de niveau. En effet, le degré de lissage d'une courbe dépend du nombre de points ayant servi à la générer. Le MNT spline « plaque-mince » est la méthode implémentée. Des travaux de courte durée ont été aussi menés afin d'offrir des solutions informatiques, c'est-à-dire automatisées, à des problèmes de saisie de données. Note de contenu : 1) INTRODUCTION 2) REALISATION DE LA MIGRATION - Raisons de la migration de Caltopo - Mise en oeuvre - Résultats (la nouvelle version et ses apports) 3) LISSAGE DE COURBES DE NIVEAU - Présentation du sujet - Solution et mise en oeuvre de la solution - Traitement des données - Résultats - Evolution du module de lissage 4) AUTOMATISATION DE LA SAISIE DES FICHES DE CANEVAS (STAR) ET DES DONNEES POUR BINGO 5) CONCLUSION Numéro de notice : 30201 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Mémoire masters divers Organisme de stage : Société Topographie Informatique Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=51655

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
30201-01	MPPMD	Livre	Centre de documentation	Travaux d'élèves	Disponible

Automatisierung der kartographischen Verdrängung mittels Energieminimierung / Dirk Burghardt (2001)

Public Titre : Automatisierung der kartographischen Verdrängung mittels Energieminimierung Titre original : [Automatisation de l'élimination cartographique avec la minimalisation d'énergie] Type de document : Thèse/HDR Auteurs : Dirk Burghardt, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2001 Collection : DGK - C Sous-collection : Dissertationen num. 536 Importance : 95 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-9575-5 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] calcul variationnel [Termes IGN] cartographie numérique [Termes IGN] conflit d'espace [Termes IGN] déplacement d'objet géographique [Termes IGN] données vectorielles [Termes IGN] factorisation de Cholesky [Termes IGN] fonction spline [Termes IGN] formule d'Euler [Termes IGN] généralisation cartographique automatisée [Termes IGN] objet géographique linéaire [Termes IGN] objet géographique ponctuel [Termes IGN] objet géographique zonal Résumé : (Auteur) With the help of highly advanced cartographic software programs it is possible to produce topographic maps from digital data. In some cases, however, there exist graphical conflicts, because symbol widths require more space than their real-size equivalents. Generalization of such objects by manual editing is rather time-consuming. Therefore, automation of generalization operations is desirable and should be possible in the age of information technology. Automated cartographic displacement of vector data distinguishes between point, line and area objects subject to processing. Modeling of line objects assumes a central position, because the human eye is extremely sensitive to shape alterations caused by displacement. In many applications splines are well-known tool for describing lines. It is especially the energy-minimizing spline also called snakes model shape deformation as a result of external forces. The internal energy is used to maintain the line shape which has been displaced due to conflicts. First and second derivatives of the line coordinates with respect to the are length are used as quality measures. In cartographic displacement a minimal distance between adjacent objects should be maintained. The external energy is used to describe the conflict situation if objects are too close to each other. To solve the graphic conflicts while maintaining the shape of the objects, the method of energy minimization is employed. Minimizing the energy functional of internal and external energy leads to two independent Euler equations. These are discretized by means of finite differences. The equations can be solved iteratively using the Cholesky factorization. Parametrization of the energy-minimizing splines by means of the tangent angle function (tafus) replaces the two eulerian equations of the 4th order with one equation of the 2nd order. Simplification of the equation system requires an additional amount of calculation for transforming the resulting changes of line direction to attain cartesian coordinates. Verification of a desirably faster convergence has yet to be achieved. The Greedy Algorithm is an alternative procedure to accomplish energy minimization using the Variational Calculus. With the aid of this algorithm the energy of each individual support point is minimized by way of minor displacements. As opposed to the Variational Calculus the effects are more local. Therefore, the Greedy Algorithm is advantageous used for the displacement of buildings or for the positioning of label boxes. The integration of this displacement approach in a cartographic program provides evidence of the fact that it can be used in practical applications. Cooperation with a software producer will help to find additional fields of application, a case in point being the automated map edge work which allows displacement and suppression of text and symbols at the map boundaries. Experience has shown that the research effort required for developing new software tools is estimated to amount to between 30 and 50 percent of the total effort. Numéro de notice : 27829 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=56453

Réservation

Réserver ce document

Exemplaires (2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
27829-02	37.10	Livre	Centre de documentation	Géomatique	Disponible
27829-01	37.10	Livre	Centre de documentation	Géomatique	Disponible

Estimation par moindres carrés / Patrick Sillard (2001)

Permalink

A processing strategy for the application of the GPS in networks / P.J. DE Jonge (1998)

Permalink

Théorie des erreurs : Estimation de R grandeurs inconnues à partir de N grandeurs observées par la méthode des moindres carrés / Philippe Hottier (1985) 

Permalink

Algorithmes et programmes / Joël Van Cranenbroeck in XYZ, n° 18 (mars - mai 1984)

Permalink

Analyse numérique linéaire / Jean-Philippe Grelot (1983)

Permalink

Pose et traitement des relations d'observation en géodésie / Pacôme Delva (1982)

Permalink

Numerical aspects of orbit computation using series of Kernel functions / H. Hauck (1979)

Permalink

Grands systèmes linéaires / Georges Balmino (1977)

Permalink

Résolution des grands systèmes linéaires / H.M. Dufour (01/08/1975)

Permalink

La résolution des systèmes d'équations par approximations successives / J. Delmoitie (1975)

Permalink