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Bias in least-squares adjustment of implicit functional models / Michael Lösler in Survey review, Vol 53 n° 378 (May 2021)  

Public [article]  inSurvey review > Vol 53 n° 378 (May 2021) . - pp 223 - 234 Titre : Bias in least-squares adjustment of implicit functional models Type de document : Article/Communication Auteurs : Michael Lösler, Auteur ; Rüdiger Lehmann, Auteur ; Frank Neitzel, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 223 - 234 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] compensation par moindres carrés [Termes IGN] erreur systématique [Termes IGN] fonction de Bessel [Termes IGN] méthode de Monte-Carlo [Termes IGN] modèle non linéaire [Termes IGN] modèle stochastique [Termes IGN] série de Taylor [Termes IGN] substitution [Termes IGN] transformation de coordonnées Résumé : (auteur) To evaluate the benefit of a measurement procedure onto the estimated parameters, the dispersion of the parameters is usually used. To draw objective conclusions, unbiased or at least almost unbiased estimates are required. In geodesy, most of the functional relations are nonlinear but the statistical properties of the estimates are usually obtained by a linearised substitute-problem. Since the statistical properties of linear models cannot be passed to the nonlinear case, the estimates are biased. In this contribution, the bias of the parameters as well as the bias of the dispersion in nonlinear implicit models is investigated, using a second-order Taylor expansion. Nonlinear implicit models are general models and are used, for instance, in the framework of surface-fitting or coordinate transformation, which considers errors for the coordinates in source and target system. The bias is introduced as a further indicator to validate the benefit of an adapted measurement process using more precise measuring instruments. Since some parametrisations yield an ill-posed problem, also the case of a singular equation system is investigated. To demonstrate the second-order effect onto the estimates, a best-fitting plane is adjusted under varying configurations. Such a configuration is recommended in evaluating uncertainties of optical 3D measuring systems, e.g. in the framework of the VDI/VDE 2634 guideline. The estimated bias is used as an indicator whether a large number of poor observations provides better results than a small but precise sample. Numéro de notice : A2021-404 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2020.1715680 date de publication en ligne : 29/01/2020 En ligne : https://doi.org/10.1080/00396265.2020.1715680 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97717 [article]

Multi-dimensional particle filter-based estimation of inter-system phase biases for multi-GNSS real-time integer ambiguity resolution / Yumiao Tian in Journal of geodesy, vol 93 n°7 (July 2019)  

Public [article]  inJournal of geodesy > vol 93 n°7 (July 2019) . - pp 1073 - 1087 Titre : Multi-dimensional particle filter-based estimation of inter-system phase biases for multi-GNSS real-time integer ambiguity resolution Type de document : Article/Communication Auteurs : Yumiao Tian, Auteur ; Zhizhao Liu, Auteur ; Frank Neitzel, Auteur Année de publication : 2019 Article en page(s) : pp 1073 - 1087 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] ambiguïté entière [Termes IGN] analyse multidimensionnelle [Termes IGN] constellation GNSS [Termes IGN] erreur systématique inter-systèmes [Termes IGN] filtre [Termes IGN] phase GNSS [Termes IGN] positionnement par GNSS [Termes IGN] précision du positionnement [Termes IGN] résolution d'ambiguïté [Termes IGN] temps réel [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) In multi-GNSS integration, fixing inter-system double-difference ambiguities to integers is still a challenge due to the existence of inter-system biases (ISB) when mixed types of GNSS receivers are used. It has been shown that when ISB is known, the inter-system ambiguities can be fixed and the reliability of ambiguity fixing can be improved significantly, especially under poor conditions when the number of observed satellites is small. In traditional methods, the intra-system ambiguity is fixed first; then, the ISB is estimated to ultimately fix the inter-system ambiguity. In our work, we use the particle filter-based method to estimate the ISB parameter and fix the inter-system ambiguities to integers at the same time. This method shows higher reliability and higher ambiguity fixing rate. Nevertheless, the existing particle filter approach for ISB parameter estimation is a one-dimensional algorithm. When satellites from three or more systems are observed, there are two or more ISB parameters. We extend the current one-dimensional particle filter approach to multi-dimensional case and estimate multi-ISB parameters in this study. We first present a multi-dimensional particle filter approach that can estimate multi-ISB parameters simultaneously. We also show that the RATIO values can be employed to judge the quality of multi-dimensional ISB values. Afterward, a two-dimensional particle filter approach is taken as an example to validate this approach. For example, in the experiment of GPS L5, Galileo E5a and QZSS L5 integration with 6 satellites using the IGS baseline SIN0-SIN1, only three ambiguities are resolved to integer when the ISBs are unknown. The integer ambiguity fixing rate is 41.0% with 53% of the ambiguity-fixed solutions having positioning errors larger than 3 cm. However, when our approach is adopted, the number of integer ambiguity parameters increases to five. The integer ambiguity fixing rate increases to 99.7% with 100% of ambiguity-fixed solutions having positioning errors smaller than 3 cm. Numéro de notice : A2019-359 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-01226-6 date de publication en ligne : 29/01/2019 En ligne : https://doi.org/10.1007/s00190-018-01226-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93427 [article]

Determining inter-system bias of GNSS signals with narrowly spaced frequencies for GNSS positioning / Yumiao Tian in Journal of geodesy, vol 92 n° 8 (August 2018)  

Public [article]  inJournal of geodesy > vol 92 n° 8 (August 2018) . - pp 873 - 887 Titre : Determining inter-system bias of GNSS signals with narrowly spaced frequencies for GNSS positioning Type de document : Article/Communication Auteurs : Yumiao Tian, Auteur ; Zhizhao Liu, Auteur ; Maorong Ge, Auteur ; Frank Neitzel, Auteur Année de publication : 2018 Article en page(s) : pp 873 - 887 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] double différence [Termes IGN] erreur systématique inter-systèmes [Termes IGN] fréquence [Termes IGN] positionnement par GNSS [Termes IGN] signal GLONASS [Termes IGN] signal GNSS [Termes IGN] signal GPS Résumé : (Auteur) Relative positioning using multi-GNSS (global navigation satellite systems) can improve accuracy, reliability, and availability compared to the use of a single constellation system. Intra-system double-difference (DD) ambiguities (ISDDAs) refer to the DD ambiguities between satellites of a single constellation system and can be fixed to an integer to derive the precise fixed solution. Inter-system ambiguities, which denote the DD ambiguities between different constellation systems, can also be fixed to integers on overlapping frequencies, once the inter-system bias (ISB) is removed. Compared with fixing ISDDAs, fixing both integer intra- and inter-system DD ambiguities (IIDDAs) means an increase of positioning precision through an integration of multiple GNSS constellations. Previously, researchers have studied IIDDA fixing with systems of the same frequencies, but not with systems of different frequencies. Integer IIDDAs can be determined from single-difference (SD) ambiguities, even if the frequencies of multi-GNSS signals used in the positioning are different. In this study, we investigated IIDDA fixing for multi-GNSS signals of narrowly spaced frequencies. First, the inter-system DD models of multi-GNSS signals of different frequencies are introduced, and the strategy for compensating for ISB is presented. The ISB is decomposed into three parts: 1) a float approximate ISB number that can be considered equal to the ISB of code pseudorange observations and thus can be estimated through single point positioning (SPP); 2) a number that is a multiple of the GNSS signal wavelength; and 3) a fractional ISB part, with a magnitude smaller than a single wavelength. Then, the relationship between intra- and inter-system DD ambiguity RATIO values and ISB was investigated by integrating GPS L1 and GLONASS L1 signals. In our numerical analyses with short baselines, the ISB parameter and IIDDA were successfully fixed, even if the number of observed satellites in each system was small. Numéro de notice : A2018-456 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1100-4 date de publication en ligne : 14/12/2017 En ligne : https://doi.org/10.1007/s00190-017-1100-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91053 [article]

Identification of stable areas in unreferenced laser scans for deformation measurement / Daniel Wujanz in Photogrammetric record, vol 31 n° 155 (September - November 2016)  

Public [article]  inPhotogrammetric record > vol 31 n° 155 (September - November 2016) . - pp 261 - 280 Titre : Identification of stable areas in unreferenced laser scans for deformation measurement Type de document : Article/Communication Auteurs : Daniel Wujanz, Auteur ; Daniel Krueger, Auteur ; Frank Neitzel, Auteur Année de publication : 2016 Article en page(s) : pp 261 - 280 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] calage [Termes IGN] congruence [Termes IGN] géoréférencement [Termes IGN] semis de points [Termes IGN] système de référence géodésique [Termes IGN] valeur aberrante Résumé : (Auteur) A current aim of ongoing research in the field of deformation measurement is to automatically determine geometric changes between several epochs with data captured by terrestrial laser scanners. A critical component within the process chain of deformation measurement is the transformation of captured point clouds into a reference coordinate system. This contribution proposes a surface-based alignment methodology that does not require artificial targets or extracted geometric primitives. A diagnostic method reveals deformations that occurred in between epochs and rejects them from the computation of transformation parameters that would otherwise cause erroneous registrations. The novel approach has been successfully tested on two practical cases where the highest degree of deformation extended to 65% of the total surface area. Numéro de notice : A2016-721 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : 10.1111/phor.12152 date de publication en ligne : 27/06/2016 En ligne : https://doi.org/10.1111/phor.12152 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82244 [article]

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Identifizierung konsistenter Datengruppen am Beispiel der Kongruenzuntersuchung geodätischer Netze / Frank Neitzel (2004)

Public Titre : Identifizierung konsistenter Datengruppen am Beispiel der Kongruenzuntersuchung geodätischer Netze Titre original : [Identification de groupes de données cohérentes par l'exemple de l'étude de la congruence des réseaux géodésiques] Type de document : Thèse/HDR Auteurs : Frank Neitzel, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2004 Collection : DGK - C Sous-collection : Dissertationen num. 565 Importance : 148 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5004-4 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] cohérence des données [Termes IGN] compensation de coordonnées [Termes IGN] congruence [Termes IGN] méthode des moindres carrés [Termes IGN] réseau géodésique [Termes IGN] transformation de coordonnées [Termes IGN] transformation de Helmert Note de contenu : 1) Einleitung und Uberblick 2) Koordinaten und Transformationen 3) Methoden der Parameterschätzung 4) Kongruenzuntersuchung geodätischer Netze 5) MSS - die Methode der Maximalen Untergruppe 6) Schussbetrachtung Numéro de notice : 13189 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54904

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