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Testing impact of the strategy of VLBI data analysis on the estimation of Earth Orientation Parameters and station coordinates / Agata Wielgosz in Reports on geodesy and geoinformatics, vol 101 (June 2016)  

Public [article]  inReports on geodesy and geoinformatics > vol 101 (June 2016) . - pp 1 - 15 Titre : Testing impact of the strategy of VLBI data analysis on the estimation of Earth Orientation Parameters and station coordinates Type de document : Article/Communication Auteurs : Agata Wielgosz, Auteur ; Monika Tercjak, Auteur ; Alexander Brzezinski, Auteur Année de publication : 2016 Article en page(s) : pp 1 - 15 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données ITGB [Termes IGN] interférométrie à très grande base [Termes IGN] paramètres d'orientation de la Terre [Termes IGN] pondération [Termes IGN] station permanente Résumé : (Auteur) Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable to realise the Celestial Reference Frame and tie it with the Terrestrial Reference Frame. It is also the only technique, which measures all the Earth Orientation Parameters (EOP) on a regular basis, thus the role of VLBI in determination of the universal time, nutation and polar motion and station coordinates is invaluable. Although geodetic VLBI has been providing observations for more than 30 years, there are no clear guidelines how to deal with the stations or baselines having significantly bigger post-fit residuals than the other ones. In our work, we compare the common weighting strategy, using squared formal errors, with strategies involving exclusion or down-weighting of stations or baselines. For that purpose, we apply the Vienna VLBI Software VieVS with necessary additional procedures. In our analysis, we focus on statistical indicators that might be the criterion of excluding or down-weighting the inferior stations or baselines, as well as on the influence of adopted strategy on the EOP and station coordinates estimation. Our analysis shows that in about 99% of 24-hour VLBI sessions there is no need to exclude any data as the down-weighting procedure is sufficiently efficient. Although results presented here do not clearly indicate the best algorithm, they show strengths and weaknesses of the applied methods and point some limitations of automatic analysis of VLBI data. Moreover, it is also shown that the influence of the adopted weighting strategy is not always clearly reflected in the results of analysis. Numéro de notice : A2016-649 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/rgg-2016-0017 En ligne : http://dx.doi.org/10.1515/rgg-2016-0017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81867 [article]

Optimization of observation plan based on the stochastic characteristics of the geodetic network / Wojciech Pachelski in Reports on geodesy and geoinformatics, vol 101 (June 2016)  

Public [article]  inReports on geodesy and geoinformatics > vol 101 (June 2016) . - pp 16 - 26 Titre : Optimization of observation plan based on the stochastic characteristics of the geodetic network Type de document : Article/Communication Auteurs : Wojciech Pachelski, Auteur ; Paweł Postek, Auteur Année de publication : 2016 Article en page(s) : pp 16 - 26 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] coût [Termes IGN] matrice de covariance [Termes IGN] optimisation (mathématiques) [Termes IGN] réseau géodésique planimétrique Résumé : (Auteur) Optimal design of geodetic network is a basic subject of many engineering projects. An observation plan is a concluding part of the process. Any particular observation within the network has through adjustment a different contribution and impact on values and accuracy characteristics of unknowns. The problem of optimal design can be solved by means of computer simulation. This paper presents a new method of simulation based on sequential estimation of individual observations in a step-by-step manner, by means of the so-called filtering equations. The algorithm aims at satisfying different criteria of accuracy according to various interpretations of the covariance matrix. Apart of them, the optimization criterion is also amount of effort, defined as the minimum number of observations required. A numerical example of a 2-D network is illustrated to view the effectiveness of presented method. The results show decrease of the number of observations by 66% with respect to the not optimized observation plan, which still satisfy the assumed accuracy. Numéro de notice : A2016-650 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/rgg-2016-0018 En ligne : http://dx.doi.org/10.1515/rgg-2016-0018 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81868 [article]

Assessment of continental hydrosphere loading using GNSS measurements / Michał Zygmunt in Reports on geodesy and geoinformatics, vol 101 (June 2016)  

Public [article]  inReports on geodesy and geoinformatics > vol 101 (June 2016) . - pp 36 - 53 Titre : Assessment of continental hydrosphere loading using GNSS measurements Type de document : Article/Communication Auteurs : Michał Zygmunt, Auteur ; Marcin Rajner, Auteur ; Tomasz Liwosz, Auteur Année de publication : 2016 Article en page(s) : pp 36 - 53 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] déformation de la croute terrestre [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] données GNSS [Termes IGN] fonction de Green [Termes IGN] modèle hydrographique [Termes IGN] série temporelle [Termes IGN] station permanente [Termes IGN] surcharge océanique Résumé : (Auteur) Presented paper is dedicated to problems of deformation of the Earth's crust as a response to the surface loading caused by continental waters. The aim of this study was to specify areas particularly vulnerable to studied deformation and to compare calculated and observed displacements. Information of the continental water volume was taken from the WaterGAP Global Hydrological Model. Calculated values of the deformations were verified with the results obtained with programs SPOTL and grat. Vertical deformations were almost 10 times higher than the deformation in the horizontal plane, for which reason later part of the paper focuses on the former. In order to check agreement of the calculated and observed deformation 23 stations of International GNSS Service (IGS) were selected and divided into three groups (inland, near the shoreline and islands). Before comparison outliers and discontinuities were removed from GNSS observations. Modelled and observed signals were centred. The analysed time series of the vertical displacements showed that only for the inland stations it is possible to effectively remove displacements caused by mass transfer in the hydrosphere. For stations located in the coastal regions or islands, it is necessary to consider additional movement effects resulting from indirect ocean tidal loading or atmosphere loading. Numéro de notice : A2016-651 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/rgg-2016-0020 En ligne : http://dx.doi.org/10.1515/rgg-2016-0020 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81870 [article]

A concept for the examination of reference points stability in horizontal control networks / Ryszard Malarski in Reports on geodesy and geoinformatics, vol 101 (June 2016)  

Public [article]  inReports on geodesy and geoinformatics > vol 101 (June 2016) . - pp 60 - 69 Titre : A concept for the examination of reference points stability in horizontal control networks Type de document : Article/Communication Auteurs : Ryszard Malarski, Auteur Année de publication : 2016 Article en page(s) : pp 60 - 69 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie [Termes IGN] barrage [Termes IGN] compensation de coordonnées [Termes IGN] point de repère [Termes IGN] réseau géodésique planimétrique [Termes IGN] réseau géodésique spécifique [Termes IGN] stabilité Résumé : (Auteur) This paper presents a concept for the identification of stable reference points used in horizontal control networks, which is based on the lengths of apparent displacement vectors and their mean errors. These vectors and their mean errors are obtained during the process of calculating displacements with free adjustment conditions. It will be shown that the influence of the apparent displacement vectors has a significant effect on the calculation of results. The identification of stable points, using the proposed method, is an integral part of the adjustment process and allows for the interrogation the influence of individual point inclusion or deletion from the reference database, on the values of displacements of controlled points. A detailed process of stable reference points identification is presented using the example of a linear-angular network for a barrage. Numéro de notice : A2016-652 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/rgg-2016-0022 En ligne : http://dx.doi.org/10.1515/rgg-2016-0022 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81871 [article]

Comparison of robust estimators for leveling networks in Monte Carlo simulations / Maria Pokarowska in Reports on geodesy and geoinformatics, vol 101 (June 2016)  

Public [article]  inReports on geodesy and geoinformatics > vol 101 (June 2016) . - pp 70 - 81 Titre : Comparison of robust estimators for leveling networks in Monte Carlo simulations Type de document : Article/Communication Auteurs : Maria Pokarowska, Auteur Année de publication : 2016 Article en page(s) : pp 70 - 81 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Nivellement [Termes IGN] méthode de Monte-Carlo [Termes IGN] méthode des moindres carrés [Termes IGN] méthode robuste [Termes IGN] réseau de nivellement [Termes IGN] valeur aberrante Résumé : (Auteur) We compared the method of least squares (LS), Pope’s iterative data snooping (IDS) and Huber’s M-estimator (HU) in realistic leveling networks, for which the heights or the vertical displacements of points are known. The study was conducted using the Monte Carlo simulation, in which one repeatedly generates sets of observations related to the measurement data, then calculates values of the estimators and, finally, assesses it with respect to the real coordinates. To simulate outliers we used popular mixture models with two or more normal distributions. It is shown that for small, strong networks robust methods IDS and HU are more accurate than LS, but for large, weak networks occurring in practice there is no significant difference between the considered methods in the accuracy of the solution. Numéro de notice : A2016-653 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/rgg-2016-0023 En ligne : http://dx.doi.org/10.1515/rgg-2016-0023 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81872 [article]