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Weighted total least squares for solving non-linear problem: GNSS point positioning / S. Jazaeri in Survey review, vol 47 n° 343 (July 2015)  

Public [article]  inSurvey review > vol 47 n° 343 (July 2015) . - pp 265 - 271 Titre : Weighted total least squares for solving non-linear problem: GNSS point positioning Type de document : Article/Communication Auteurs : S. Jazaeri, Auteur ; Ali Reza Amiri-Simkooei, Auteur Année de publication : 2015 Article en page(s) : pp 265 - 271 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] erreur de mesure [Termes IGN] estimation des paramètres [Termes IGN] matrice de covariance [Termes IGN] méthode des moindres carrés [Termes IGN] modèle non linéaire [Termes IGN] pondération [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis Résumé : (auteur) In this contribution, two algorithms are developed for parameter estimation in a non-linear measurement error model with errors in both the coefficient matrix and the vector of measurement. They are based on the complete description of the variance–covariance matrices of the observation errors and of the coefficient matrix errors without any restriction. The paper reinvestigates the nonlinear measurement model associated with GNSS point positioning. Various simulation experiments indicate that GNSS point positioning is much better formulated as a non-linear WTLS problem with errors in both the coefficient matrix and measurement variables. The efficacy of the proposed algorithms is verified through the numerical results. Numéro de notice : A2015-920 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000132 En ligne : https://doi.org/10.1179/1752270614Y.0000000132 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79730 [article]

Divisional ambiguity resolution for long range reference stations in network RTK / J. Deng in Survey review, vol 47 n° 343 (July 2015)  

Public [article]  inSurvey review > vol 47 n° 343 (July 2015) . - pp 272 - 278 Titre : Divisional ambiguity resolution for long range reference stations in network RTK Type de document : Article/Communication Auteurs : J. Deng, Auteur ; S.L. Wang, Auteur Année de publication : 2015 Article en page(s) : pp 272 - 278 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] analyse comparative [Termes IGN] fractionnement [Termes IGN] ligne de base [Termes IGN] positionnement cinématique en temps réel [Termes IGN] résolution d'ambiguïté [Termes IGN] station permanente Résumé : (auteur) Increasing the distance between reference stations of network RTK can improve the flexibility of the reference stations sitting, reduce the number of reference stations and cut down construction and maintenance costs. However, it also decreases the correlation of spatial error and affects the real time performance and effectiveness of the network RTK positioning. Thus, the key techniques of long range network RTK need to be further optimised. Ambiguity resolution between reference stations is one of the most critical techniques. In this paper a divisional ambiguity resolution for long range reference stations of network RTK is proposed, so as to deal with the long fixed time and low success rate, especially for low elevation satellites. Based on conventional two-step ambiguity resolution, firstly, this new method calculates the wide-lane ambiguity by building M-W combination of pseudo-range and carrier observations. Second, the conventional ambiguity resolution as a whole is changed and satellites are divided into high elevation ones and low elevation ones, then the integer ambiguity of high elevation satellites is resolved by means of ionosphere-free combination with the relative zenith wet delay as a parameter. Finally, the Kalman filter model is established by the observation equation of high elevation satellites with calculated ambiguity and low elevation satellites, assisting to obtain the ambiguity of low elevation satellites quickly. The example selects a 196 km long baseline for comparative analysis. Result shows that it takes 733 s to resolve the ambiguity of all satellites by conventional ambiguity resolution in whole, and 252 s by divisional ambiguity resolution proposed in this paper. The new method saves about two thirds of resolution time, and also greatly improves the efficiency of ambiguity resolution of low elevation satellites for long baseline. Numéro de notice : A2015-921 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000123 En ligne : https://doi.org/10.1179/1752270614Y.0000000123 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79732 [article]

Detection of high speed railway track static regularity with laser trackers / L. Yao in Survey review, vol 47 n° 343 (July 2015)  

Public [article]  inSurvey review > vol 47 n° 343 (July 2015) . - pp 279 - 285 Titre : Detection of high speed railway track static regularity with laser trackers Type de document : Article/Communication Auteurs : L. Yao, Auteur ; H. Sun, Auteur ; Y. Zhou, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 279 - 285 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] capteur à balayage [Termes IGN] précision submillimétrique [Termes IGN] statique [Termes IGN] surveillance d'ouvrage [Termes IGN] train à grande vitesse [Termes IGN] voie ferrée Résumé : (auteur) Track regularity is of vital importance in the safety of high speed railway operation. A laser tracker can collect highly accurate three-dimensional (3D) point measurements. Therefore, it is considered as a promising surveying technique for the detection of railway track static irregularity as opposed to using a total station. This study proposes a new approach that uses a laser tracker as the main sensor for obtaining the coordinates of left- and right-track points to detect potential track static irregularities. In this method, the reflecting target of the laser tracker is on a track inspection trolley moving in a round trip along the railway track. A field experiment was conducted to validate the results by comparing the results with the field measurements gathered using a track inspection trolley. The results show that the track static regularity detection method with laser trackers is feasible and indicate that track geometry parameters such as gauges, elevations and lateral deviations of centreline, superelevations, lateral profiles and vertical profiles obtained using the laser tracker and a track inspection trolley are in a good agreement. The average of deviations of track centreline elevations, lateral deviations, and gauges are 0·8, 0·7 and 0·3 mm. Numéro de notice : A2015-922 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000135 En ligne : https://doi.org/10.1179/1752270614Y.0000000135 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79733 [article]