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Algebraic method to speed up robust algorithms: example of laser-scanned point clouds / B. Palancz in Survey review, vol 49 n° 357 (December 2017)  

Public [article]  inSurvey review > vol 49 n° 357 (December 2017) . - pp 408 - 418 Titre : Algebraic method to speed up robust algorithms: example of laser-scanned point clouds Type de document : Article/Communication Auteurs : B. Palancz, Auteur ; Joseph L. Awange, Auteur ; T. Lovas, Auteur ; R. Lewis, Auteur ; B. Molnar, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 408 - 418 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] bases de Gröbner [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] méthode du maximum de vraisemblance (estimation) [Termes IGN] Ransac (algorithme) [Termes IGN] reconstruction d'objet [Termes IGN] semis de points [Termes IGN] valeur aberrante Résumé : (auteur) Surface reconstruction from point clouds generated by laser scanning technology has become a fundamental task in many fields of geosciences, such as robotics, computer vision, digital photogrammetry, computational geometry, digital building modelling, forest planning and operational activities. Point clouds produced by laser scanning, however, are limited due to the occurrence of occlusions, multiple reflectance and noise, and off-surface points (outliers), thus necessitating the need for robust fitting techniques. In this contribution, a fast, non-iterative and data invariant algebraic algorithm with constant O(1) complexity that fits planes to point clouds in the total least squares sense using Gaussian-type error distribution is proposed. The maximum likelihood estimator method is used, resulting in a multivariate polynomial system that is solved in an algebraic way. It is shown that for plane fitting when datasets are affected heavily by outliers, the proposed algebraic method can be embedded into the framework of robust methods like the Danish or the RANdom SAmple Consensus methods and computed in parallel to provide rigorous algebraic fitting with significantly reduced running times. Compared to the embedded traditional singular value decomposition and principal component analysis approaches, the performance of the proposed algebraic algorithm demonstrated its efficiency on both synthetic data and real laser-scanned measurements. The evaluation of a symbolic algebraic formula is practically independent of the values of its coefficients; however, the computation of the coefficients depends on the complexity of the data. Since the main advantage of the symbolic solution is its non-requirement of numerical iteration, the data complexity will have weak influence on the speed-up. The novelty of the proposed method is the use of algebraic technique in a robust plane fitting algorithm that could be applied to remote sensing data analysis/delineation/classification. In general, the method could be applied to most plane fitting problems in the geoscience field. Numéro de notice : A2017-755 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/00396265.2016.1183939 En ligne : https://doi.org/10.1080/00396265.2016.1183939 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89109 [article]

A Realistic and Easy-to-Implement Weighting Model for GPS Phase Observations / Xiaoguang Luo in IEEE Transactions on geoscience and remote sensing, vol 52 n° 10 tome 1 (October 2014)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 52 n° 10 tome 1 (October 2014) . - pp 6110 - 6118 Titre : A Realistic and Easy-to-Implement Weighting Model for GPS Phase Observations Type de document : Article/Communication Auteurs : Xiaoguang Luo, Auteur ; M. Mayer, Auteur ; B. Heck, Auteur ; Joseph L. Awange, Auteur Année de publication : 2014 Article en page(s) : pp 6110 - 6118 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] phase GPS [Termes IGN] pondération [Termes IGN] rapport signal sur bruit [Termes IGN] signal GPS Résumé : (Auteur) Observation weighting is an essential component of GPS stochastic modeling and plays a key role in reliable outlier detection and parameter estimation. Nowadays, satellite elevation angle and SNR are used as quality indicators for GPS phase measurements in high-accuracy geodetic applications. In comparison with elevation-dependent models, SNR-based weighting schemes represent the reality better, but usually require greater implementation efforts. Relying upon a representative analysis of empirical SNR-based weights, this paper proposes the elevation-dependent exponential weighting function EXPZ, which benefits from realistic SNR-based weights and enables easy software implementation. To process GPS data from a regional network, this advanced weighting scheme is implemented in the Bernese GPS Software 5.0 and is compared with the conventional elevation-dependent COSZ model in terms of phase ambiguity resolution, troposphere parameter (TRP) estimation, and site coordinate determination. The results show that the proposed EXPZ model significantly attenuates the downweighting effects on low-elevation observations and improves the success rates of ambiguity resolution by about 10%, the standard deviations of site-specific TRPs by about 40%, and the repeatability of daily coordinate estimates by up to 2.3 mm (50%). Numéro de notice : A2014-481 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2013.2294946 En ligne : https://doi.org/10.1109/TGRS.2013.2294946 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74063 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
065-2014101A	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Solving algebraic computational problems in geodesy and geoinformatics / Joseph L. Awange (2005)

Public Titre : Solving algebraic computational problems in geodesy and geoinformatics : The answer to modern challenges Type de document : Monographie Auteurs : Joseph L. Awange, Auteur ; Erik W. Grafarend, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2005 Importance : 334 p. Format : 16 x 24 cm ISBN/ISSN/EAN : 978-3-540-23425-8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie [Termes IGN] anneau [Termes IGN] coordonnées cartésiennes géocentriques [Termes IGN] coordonnées ellipsoïdales [Termes IGN] géomètrie algorithmique [Termes IGN] modèle de Gauss-Markov [Termes IGN] Ploynôme [Termes IGN] positionnement par GPS [Termes IGN] relèvement [Termes IGN] transformation de coordonnées [Termes IGN] transformation géométrique [Termes IGN] valeur aberrante Index. décimale : 30.04 Mathématiques appliquées à la géodésie Résumé : (Editeur) The book presents modern and efficient methods for solving Geodetic and Geoinformatics algebraic problems using computer algebra techniques of Ring, polynomials, Groebner basis, resultants, Gauss-Jacobi combinatorial and Procrustes algorithms. Although these problems are traditionally solved by approximate methods, this book presents alternative algebraic techniques based on computer algebra tools. This new approach meets such modern challenges as resection by laser techniques, solution of orientation in robotics, transformation and bundle block adjustment in geoinformatics, densification of engineering networks, analytical solution for GPS-meteorology and many other problems. For mathematicians the book provides some practical examples of abstract algebra application and multidimensional scaling. Note de contenu : 1. Introduction 2. Basics of Ring Theory 3. Basics of Polynominal Theory 4. Groebner Basis 5. Polynomial resultants 6. Gauss-Jacobi Combinatorial algorithm 7. Local versus Global Positioning Systems 8. Partial procrustes and the orientation problem 9. Positioning by ranging 10. From geocentric cartesian to ellipsoidal coordinates 11. Positioning by resection method 12. Positioning by intersection method 13. GPS Meteorology in environmental monitoring 14. Algebraic diagnosis of outliers 15. Transformation problem : procustes algorithm 2 16. Computer algebra systems. Numéro de notice : 12687 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54752

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
12687-01	30.04	Livre	Centre de documentation	En réserve M-103	Disponible