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A search step optimization in an ambiguity function-based GNSS precise positioning / Sławomir Cellmer in Survey review, vol 54 n° 383 (March 2022)  

Public [article]  inSurvey review > vol 54 n° 383 (March 2022) . - pp 117 - 124 Titre : A search step optimization in an ambiguity function-based GNSS precise positioning Type de document : Article/Communication Auteurs : Sławomir Cellmer, Auteur ; Krzysztof Nowel, Auteur ; Artur Fischer, Auteur Année de publication : 2022 Article en page(s) : pp 117 - 124 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] ambiguïté entière [Termes IGN] diagramme de Voronoï [Termes IGN] modèle mathématique [Termes IGN] optimisation (mathématiques) [Termes IGN] positionnement par GNSS [Termes IGN] précision du positionnement Résumé : (auteur) The search procedure, as a part of the Modified Ambiguity Function Approach (MAFA), is conducted in the coordinate space. The main advantage of searching for a fixed solution in the coordinate domain, instead of in the ambiguity domain, is the constant search space dimension, which amounts to three. In contrast, an ambiguity space dimension can presently achieve over twenty when the positioning is based on multi-system data. Thus, in the MAFA method, the computational complexity is independent of the number of satellites. We propose a new method of estimating the length of the search step. In this method, the actual satellite configuration determines the size of the search step. Therefore, the data-driven search step is always optimal, regardless of the current satellite configuration. The mathematical model of the new approach is provided together with a detailed algorithm. The numerical experiment follows the description of the search procedure. Numéro de notice : A2022-239 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2021.1885947 Date de publication en ligne : 17/02/2021 En ligne : https://doi.org/10.1080/00396265.2021.1885947 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100163 [article]

Mixed integer–real least squares estimation for precise GNSS positioning using a modified ambiguity function approach / Krzysztof Nowel in GPS solutions, vol 22 n° 1 (January 2018)    

Public [article]  inGPS solutions > vol 22 n° 1 (January 2018) Titre : Mixed integer–real least squares estimation for precise GNSS positioning using a modified ambiguity function approach Type de document : Article/Communication Auteurs : Krzysztof Nowel, Auteur ; Sławomir Cellmer, Auteur ; Dawid Kwaśniak, Auteur Année de publication : 2018 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] diagramme de Voronoï [Termes IGN] méthode des moindres carrés [Termes IGN] phase [Termes IGN] positionnement par GNSS Résumé : (auteur) Mixed integer–real least squares (MIRLS) estimation still has two open scientific problems, i.e., the validation of results and computational efficiency for a large number of satellites. This paper presents and discusses a non-conventional approach to MIRLS estimation, which belongs to the ambiguity function method (AFM) class. Because the solution is searched for in the constant three-dimensional coordinate domain instead of the n-dimensional ambiguity domain, the computational efficiency does not depend as much on the number of satellites as it does in conventional MIRLS estimation. Simple numerical pretests have shown that the reliability and precision of results from the presented approach and the conventional MIRLS estimation are exactly the same. Hence, the presented approach, contrary to AFM, may be treated as MIRLS estimation. Furthermore, the presented approach is a few hundred times faster than AFM and may be considered in (near) real-time GNSS positioning. In light of the above, the new field of research on MIRLS estimation may be opened. Numéro de notice : A2018-018 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0694-6 Date de publication en ligne : 06/01/2018 En ligne : https://doi.org/10.1007/s10291-017-0694-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89115 [article]

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Investigating efficacy of robust M-estimation of deformation from observation differences / Krzysztof Nowel in Survey review, vol 48 n° 346 (January 2016)  

Public [article]  inSurvey review > vol 48 n° 346 (January 2016) . - pp 21 - 30 Titre : Investigating efficacy of robust M-estimation of deformation from observation differences Type de document : Article/Communication Auteurs : Krzysztof Nowel, Auteur Année de publication : 2016 Article en page(s) : pp 21 - 30 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] analyse de données [Termes IGN] déformation géométrique [Termes IGN] estimation statistique [Termes IGN] méthode de Monte-Carlo [Termes IGN] méthode des moindres carrés [Termes IGN] modèle stochastique [Termes IGN] test de performance Résumé : (auteur) In deformation analysis of geodetic control networks, it is important to know whether the estimated displacement value of a given point is the effect of displacement or only the effect of random measurement errors. The F-test of statistical significance is used to answer this question. This test is applied both in conventional deformation analysis (CDA) based on least square (LS) estimation and in deformation analysis based on robust M-estimation. Unfortunately, the F-test is strongly flawed in the latter case. As a consequence, its results are significantly different here than assumed/expected. This paper analyses how flawed the F-test is and proposes a new solution. First, the algorithm of the global and local F-tests was derived. It was then demonstrated that for deformation analysis based on robust M-estimation, this algorithm has theoretical flaws. Next, it was shown how these problems can be solved numerically. The basis of the solutions proposed involves the use of stochastic simulations and, more specifically, the Monte Carlo (MC) method. Moreover, it was noted that other statistical test problems which also occur in deformation analysis based on robust M-estimation can be solved using present-day computers. The numerical approach can be a good support here in the selection of the proper significance level as well as in the correct performance of the test sensitivity analysis. All theoretical discussions were verified on an example simulated control network. Numéro de notice : A2016-044 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2015.1097585 En ligne : https://doi.org/10.1080/00396265.2015.1097585 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79637 [article]