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Generating statistically robust multipath stacking maps using congruent cells / Thomas Fuhrmann in GPS solutions, vol 19 n° 1 (January 2015)  

Public [article]  inGPS solutions > vol 19 n° 1 (January 2015) . - pp 83 - 92 Titre : Generating statistically robust multipath stacking maps using congruent cells Type de document : Article/Communication Auteurs : Thomas Fuhrmann, Auteur ; Xiaoguang Luo, Auteur ; Andreas Knöpfler, Auteur ; Michael Mayer, Auteur Année de publication : 2015 Article en page(s) : pp 83 - 92 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] congruence [Termes IGN] correction du trajet multiple [Termes IGN] résidu [Termes IGN] superposition [Termes IGN] trajet multiple [Termes IGN] valeur aberrante Résumé : (auteur) Multipath effects caused by reflections in the near-field and far-field of a GNSS antenna represent a major error source in static and kinematic GNSS positioning applications. Since these effects are strongly site-specific, a generally valid and practicable analytical multipath model is still lacking. In contrast, using GNSS carrier phase observation residuals, the multipath stacking (MPS) methods are able to take site-specific conditions into account. We propose an advanced approach to performing residual-based MPS in the space domain. Being superior to most conventional attempts in which stacking cells have a fixed azimuthal resolution, our suggested method makes use of congruent cells and rigorous statistical assessments in terms of outlier detection and significance evaluation of the stacked values. The advanced stacking approach is applied to representative phase residuals from static precise point positioning. The results show that the use of congruent cells allows for MPS at high elevation angles and with a fine spatial resolution. Applying the resulting MPS maps at the residual level, both near-field and far-field effects at high and low elevation angles, respectively, can be significantly mitigated. In comparison with the conventional approach, the advanced one enables a larger reduction of about 20 % in the SD of residuals. Numéro de notice : A2015-205 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-0367-7 Date de publication en ligne : 23/02/2014 En ligne : https://doi.org/10.1007/s10291-014-0367-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76018 [article]

Korrektur stationsabhängiger Fehler bei GNSS / Andreas Knöpfler (2015)  

Public Titre : Korrektur stationsabhängiger Fehler bei GNSS Type de document : Thèse/HDR Auteurs : Andreas Knöpfler, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2015 Collection : DGK - C, ISSN 0065-5325 num. 744 Importance : 177 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5156-0 Note générale : bibliographie akademisches Grades eines Doktor-Ingenieurs von der Fakultüt für Bauingenieur-, Geo- und Umweltwissenschaften des Karlsruher Instituts für Technologie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne GNSS [Termes IGN] centre de phase [Termes IGN] erreur systématique [Termes IGN] étalonnage d'instrument [Termes IGN] modèle d'erreur [Termes IGN] positionnement ponctuel précis [Termes IGN] positionnement statique [Termes IGN] résidu [Termes IGN] traitement de données GNSS [Termes IGN] trajet multiple Mots-clés libres : stacking map Index. décimale : 30.60 Géodésie spatiale Résumé : (auteur) Highly precise positioning techniques based on Global Navigation Satellite Systems (GNSS) have become a standard tool for numerous disciplines, benefitting from the continuous development of receiver equipment and the appearance of additional GNSS. In addition to the classical differential processing approach, the Precise Point Positioning (PPP) method is able to derive station coordinates with the same accuracy as a baseline setup, when sufficient observation time is available. The basis for PPP is the improved quality of external products for the GNSS data processing, for example the orbit and especially the satellite clock products of the International GNSS Service (IGS) and its analysis centers. The increased usage of GNSS comes along with higher demands on accuracy. Therefore, the modelling of important error sources in GNSS is continuously upgraded. Intensive research led to a refinement of both the functional and the stochastic model in GNSS data processing in order to enable the correction of specific error components, for example the antenna behaviour or the tropospheric delay. Despite of the improvements in GNSS modelling, multipath effects still remain as a main error source in highly precise GNSS positioning. Within this work, stacking techniques are used to correct for multipath effects and further site dependent errors, for example residual errors in the calibration values of the receiving GNSS antenna. The method developed in this work is based on zero difference PPP residuals, which are accumulated over defined azimuth-elevation cells and over a fixed period of time (here: 10 d) and introduced as correction (so-called stacking maps) in a second PPP processing run. The main purpose of this approach aims for the improvement of data, recorded on continuously operating reference stations. Within this work, two scenarios for the implementation of the corrections were investigated in detail: the combination of the stacking maps joined with the calibration information of the GNSS receiving antennas and in contrast to this approach the separate modelling of both aspects in a separate file. In order to check the effectivity of this method, the results (e.g., coordinates, residuals) before and after the introduction of the stacking maps were intensively analyzed. Within the second scenario (introduction of the correction in a separate file), the behaviour of the stacking maps over time was investigated by the analysis of so-called sliding stacking maps. Sliding stacking maps are generated as follows: calculation of a first stacking map from the residuals for example for day of year (DoY) 121 to 130 and introduction as correction for DoY 131, the next stacking map is computed from the residuals for DoY 122 to 131 and introduced for DoY 132 and so on. Especially sites with poor data quality show a significant improvement of the residual values after the implementation of stacked information. Furthermore, observations remain in the used data set, whereas they were eliminated in the processing without the introduction of stacking maps. In addition, the necessity of expensive, site-dependent individual antenna calibration was checked. The focus was on the compensating level of the stacking approach with respect to unmodelled antenna effects based on the replacement of individual receiving antenna calibrations by type mean values of the IGS in combination with stacking maps. Therefore, data of selected sites were processed using both the existing individual antenna calibration sets and the IGS type mean values. In a second processing run, the calibration sets were introduced taking the corresponding stacking information into account. Differences in the phase center variations of the antennas can be corrected by the stacking maps. Discrepancies due to differences in the phase center offsets remain in the estimated site coordinates. Numéro de notice : 14920 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD : Géodésie : Karlsruhes Institut für Technologie : 2015 DOI : 10.5445/KSP/1000045959 En ligne : https://doi.org/10.5445/KSP/1000045959 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76931