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Efficient obstruction analysis for GNSS relative positioning of terrestrial mobile mapping system / J.Y. Han in Survey review, vol 47 n° 342 (May 2015)  

Public [article]  inSurvey review > vol 47 n° 342 (May 2015) . - pp 153 - 162 Titre : Efficient obstruction analysis for GNSS relative positioning of terrestrial mobile mapping system Type de document : Article/Communication Auteurs : J.Y. Han, Auteur ; J. Guo, Auteur ; J.Y. Chuang, Auteur Année de publication : 2015 Article en page(s) : pp 153 - 162 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] interruption du signal [Termes IGN] modèle numérique de terrain [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement différentiel [Termes IGN] positionnement par GNSS [Termes IGN] prévision [Termes IGN] système de numérisation mobile Résumé : (auteur) A mobile mapping system MMS is a combination of several modern sensors and is capable of acquiring meticulous spatial information in a fast and automatic manner. However, the result obtained is highly dependent on the quality of the global navigation satellite system GNSS which is expected to constantly provide accurate positioning solutions for the system. As a consequence, in an urban or mountainous area where satellite signals are frequently obstructed by local topography, the reliability of a terrestrial MMS system is not always guaranteed. In this study, a rigorous approach for predicting GNSS satellite reception under topographic obstructions along an MMS surveyed path is developed. By utilising a digital terrain model and a lineofsight analysis, visible satellites for a moving platform are identified and used for estimating positioning quality under a GNSS relative positioning model. Based on the results from real case studies, it is illustrated that the proposed approach provides a reliable prediction for GNSS satellite obstruction and relative positioning quality. Consequently, the locations andor epochs associated with poor GNSS positioning qualities can be identified beforehand and an appropriate survey schedule can thus be arranged. Numéro de notice : A2015-929 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000110 En ligne : https://doi.org/10.1179/1752270614Y.0000000110 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79734 [article]

Irregular variations in GPS time series by probability and noise analysis / Anna Klos in Survey review, vol 47 n° 342 (May 2015)  

Public [article]  inSurvey review > vol 47 n° 342 (May 2015) . - pp 163 - 173 Titre : Irregular variations in GPS time series by probability and noise analysis Type de document : Article/Communication Auteurs : Anna Klos, Auteur ; Janusz Bogusz, Auteur ; Mariusz Figurski, Auteur ; Wieslaw Kosek, Auteur Année de publication : 2015 Article en page(s) : pp 163 - 173 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] bruit (théorie du signal) [Termes IGN] bruit blanc [Termes IGN] bruit rose [Termes IGN] classification par maximum de vraisemblance [Termes IGN] écart type [Termes IGN] filtrage du bruit [Termes IGN] métrique [Termes IGN] récepteur GPS [Termes IGN] série temporelle Résumé : (auteur) The character of the topocentric components in ETRF2000(R08) from the Polish ASG-EUPOS system was analysed using skewness and kurtosis derived from the data probability density function. The data from 115 permanent GPS stations with a time span of more than 5 years were used. The main goal of this research was to show that any unmodelled systematics can disrupt the results. The obtained median values of skewness and kurtosis clearly indicate the discrepancies between the assumed normality of the GPS time series distribution and the reality, mainly due to stochastic and/or deterministic parts that are still present in the data. The quadratic relationship between skewness and kurtosis was developed with the empirically determined constants. The noise analysis with the Maximum Likelihood Estimation was also performed with the assumptions of white and white plus power-law noise. The estimated spectral indices for power law noises are close to −1 (flicker noise). The uncertainties of the intraplate velocities with white and white plus power law noise assumptions were calculated. It was shown that these uncertainties can be underestimated up to 5 mm/year. Additionally we made 1000 simulation which were aimed at showing how the values of skewness and kurtosis are changed when some mismodelled part of the data remains in the time series. We assumed different values of trend (1 and 6 mm/year), seasonal amplitudes (1 and 6 mm) and offsets (3 and 10 mm) with flicker noise of 1 mm amplitude to see how the metrics we use are biased. Numéro de notice : A2015-930 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000133 En ligne : https://doi.org/10.1179/1752270614Y.0000000133 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79735 [article]

Application of Msplit estimation to determine control points displacements in networks with unstable reference system / M. H. Zienkiewicz in Survey review, vol 47 n° 342 (May 2015)  

Public [article]  inSurvey review > vol 47 n° 342 (May 2015) . - pp 174 - 180 Titre : Application of Msplit estimation to determine control points displacements in networks with unstable reference system Type de document : Article/Communication Auteurs : M. H. Zienkiewicz, Auteur Année de publication : 2015 Article en page(s) : pp 174 - 180 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] analyse diachronique [Termes IGN] estimation de précision [Termes IGN] point d'appui [Termes IGN] système de référence géodésique Résumé : (auteur) This paper presents the use of Msplit estimation to determine the displacements of control points in an unstable reference system. The theoretical part presents a strategy for adjusting observation sets measured in several measurement epochs using an additional (virtual) measurement epoch. The paper also includes several examples demonstrating possible applications of the method in surveying practice. The examples demonstrate the efficiency of a virtual measurement epoch in adjusting observation sets measured in an unstable reference system and also when gross errors appear in observations. Numéro de notice : A2015-931 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000105 En ligne : https://doi.org/10.1179/1752270614Y.0000000105 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79736 [article]

Combined adjustment of angle and distance measurements in a dam monitoring network / J. Casaca in Survey review, vol 47 n° 342 (May 2015)  

Public [article]  inSurvey review > vol 47 n° 342 (May 2015) . - pp 181 - 184 Titre : Combined adjustment of angle and distance measurements in a dam monitoring network Type de document : Article/Communication Auteurs : J. Casaca, Auteur ; N. Braz, Auteur ; V. Conde, Auteur Année de publication : 2015 Article en page(s) : pp 181 - 184 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] ajustement de paramètres [Termes IGN] angle [Termes IGN] barrage [Termes IGN] distance [Termes IGN] Portugal [Termes IGN] surveillance d'ouvrage Résumé : (auteur) The safety control and structural analysis of Portuguese large dams has been using, for many decades, small triangulation networks to monitor the horizontal displacements of a carefully selected set of target points on the dams. The recent surge in the use of motorised tacheometers, which enable automatic measurement of angles and distances, is changing traditional triangulation networks into combined angles/distances networks. This paper addresses the estimation of weights for the combined adjustment of angles and distances. Numéro de notice : A2015-932 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000106 En ligne : https://doi.org/10.1179/1752270614Y.0000000106 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79737 [article]