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Characterizing noise in daily GPS position time series with overlapping Hadamard variance and maximum likelihood estimation / Chang Xu in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 239 - 248 Titre : Characterizing noise in daily GPS position time series with overlapping Hadamard variance and maximum likelihood estimation Type de document : Article/Communication Auteurs : Chang Xu, Auteur ; D. Yue, Auteur Année de publication : 2017 Article en page(s) : pp 239 - 248 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] bruit (théorie du signal) [Termes IGN] bruit blanc [Termes IGN] bruit rose [Termes IGN] caractérisation [Termes IGN] Chine [Termes IGN] coordonnées GPS [Termes IGN] latitude [Termes IGN] méthode du maximum de vraisemblance (estimation) [Termes IGN] série temporelle [Termes IGN] signal aléatoire [Termes IGN] station permanente [Termes IGN] variance [Termes IGN] variance de Hadamard [Vedettes matières IGN] Traitement de données GNSS Résumé : (Auteur) We assess the noise characteristics of daily position time series (Jet Propulsion Laboratory global solutions) from 12 International GNSS Service sites located in China, using both overlapping Hadamard variance (OHVAR) and maximum likelihood estimation (MLE). The result shows that OHVAR is computationally cheap, and the dominate power-law noise inferred is in good agreement with the ones inferred by comparing MLE values. However, OHVAR is insufficient to assess the long-period noise characteristics [e.g., random walk noise (RW)]. From the MLE analysis, the RW contribution is likely to be present in 14% of the time series, while the noise of most sites are characterized by a combination of white and flicker (or power law) noise (i.e., FL + WH or PL + WH). Moreover, sites near the northern crest of the equatorial ionization anomaly have larger amplitudes of WH in the vertical component, while no clear latitude dependency is observed in FL amplitudes. Numéro de notice : A2017-547 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1163830 En ligne : https://doi.org/10.1080/00396265.2016.1163830 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86602 [article]

Mobile precise trigonometric levelling system based on land vehicle: an alternative method for precise levelling / J. Zou in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 249 - 258 Titre : Mobile precise trigonometric levelling system based on land vehicle: an alternative method for precise levelling Type de document : Article/Communication Auteurs : J. Zou, Auteur ; Y. Zhu, Auteur ; Y. Xu, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 249 - 258 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Nivellement [Termes IGN] Chine [Termes IGN] déviation de la verticale [Termes IGN] nivellement direct [Termes IGN] nivellement géométrique motorisé [Termes IGN] nivellement indirect [Termes IGN] réfraction atmosphérique [Termes IGN] tachéomètre électronique robotisé Résumé : (Auteur) The strict mathematical model of the mobile precise trigonometric levelling (MPTL) is deduced and its error sources are analysed in this paper. Some position sensors are added to instruments and observing reciprocal at the same time using two modified measuring robots so as to reduce the influence of atmospheric refraction, curvature of the earth and other factors. It is not necessary to measure the heights of instruments and targets by constructing the even numbers of observed edges to avoid errors of measuring heights. Experimental results indicate that MPTL has greatly increased the working efficiency and reduced the labour intensity compared with precise geometric levelling in the hills and mountains. A large number of experiments have proved that the standard deflection of measurement is less than and with an average speed of more than 7 kilometres per day in mountainous terrain. Numéro de notice : A2017-548 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1163877 En ligne : https://doi.org/10.1080/00396265.2016.1163877 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86604 [article]

Determining normal heights with the use of Precise Point Positioning / Grzegorz Krzan in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 259 - 267 Titre : Determining normal heights with the use of Precise Point Positioning Type de document : Article/Communication Auteurs : Grzegorz Krzan, Auteur ; Karol Dawidowicz, Auteur ; Katarzyna Stępniak, Auteur Année de publication : 2017 Article en page(s) : pp 259 - 267 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Nivellement [Termes IGN] altitude normale [Termes IGN] Napeos [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) In this paper, the authors analysed the Precise Point Positioning (PPP) performance in determination of normal heights using observations from a test network consisting of ten sites. One-week observation interval was processed using standard PPP approach and Multi-Station PPP (MS-PPP) with ambiguity resolution using the NAvigation Package for Earth Observation Satellites v. 3.3.1 software. In post-processing corrections like the Earth rotation parameters, ocean loadings, antenna phase centre offsets and variations etc. needed to obtain the most accurate position were utilised. By processing the various lengths observing sessions (1 hour, 30 minutes, 15 minutes) the authors examined the degradation of the position determination precision with shortening the observation time. In the study both high-end receivers used most often at CORS, as well as commercial two-frequency receivers were utilised. Normal heights were obtained using PL–geoid–2011 model. The results of the research show that PPP is a viable alternative for Relative GNSS Positioning in the case of GNSS levelling. Numéro de notice : A2017-549 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1164939 En ligne : https://doi.org/10.1080/00396265.2016.1164939 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86605 [article]

Periodic signals in a pseudo-kinematic GPS coordinate time series depending on the antenna phase centre model – TRM55971.00 TZGD antenna case study / Karol Dawidowicz in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 268 - 276 Titre : Periodic signals in a pseudo-kinematic GPS coordinate time series depending on the antenna phase centre model – TRM55971.00 TZGD antenna case study Type de document : Article/Communication Auteurs : Karol Dawidowicz, Auteur Année de publication : 2017 Article en page(s) : pp 268 - 276 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] antenne GNSS [Termes IGN] centre de phase [Termes IGN] étalonnage des données [Termes IGN] GPS en mode pseudo-cinématique [Termes IGN] Pologne [Termes IGN] série temporelle [Termes IGN] station permanente [Vedettes matières IGN] Traitement de données GNSS Résumé : (Auteur) This study investigates the differences between position estimates obtained using individual and type-mean (igs08.atx) antenna calibration models in GPS pseudo-kinematic processing. We used 15-min observation windows to study the short-period oscillations. Continuous GPS observations from eight selected Polish EUREF Permanent Network stations with the same TRM55971.00 TZGD antenna were used. The results showed that the differences in the calibration models, directly propagate into the position domain, affecting sub-daily results and influencing periodic variations. The sub-daily variations have periods close to half a sidereal day with amplitudes of up to 10 mm in position components. It could also be demonstrated that the mean position offsets, resulting from the use of individual calibrations instead of type-mean igs08.atx calibrations, can reach up to 5 mm in the up component, while the offsets in the horizontal components generally remain below 1 mm. Numéro de notice : A2017-550 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1166688 En ligne : https://doi.org/10.1080/00396265.2016.1166688 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86606 [article]

An iterative method for obtaining a mean 3D axis from a set of GNSS traces for use in positional controls / A. Mozas-Calvache in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 277 - 284 Titre : An iterative method for obtaining a mean 3D axis from a set of GNSS traces for use in positional controls Type de document : Article/Communication Auteurs : A. Mozas-Calvache, Auteur ; Francisco Javier Ariza-López, Auteur Année de publication : 2017 Article en page(s) : pp 277 - 284 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes IGN] axe médian [Termes IGN] classification par nuées dynamiques [Termes IGN] exploration de données géographiques [Termes IGN] incertitude géométrique [Termes IGN] itération [Termes IGN] précision de localisation [Termes IGN] trace GPS [Termes IGN] traitement de données localisées Résumé : (Auteur) This paper describes a new method of data mining for determining a 3D mean axis from a set of surveyed Global Navigation Satellite Systems traces. The purpose is to obtain a mean axis and its uncertainty in order for them to be used in line-based positional controls. The method is based on an iterative process of condensation. The final mean axis is selected when a determined level of accuracy is achieved. So the method provides a relative positional accuracy value of the final solution. The example developed in this study demonstrates the viability of this method and allows analysis of the initial size of the set needed in order to achieve a final accuracy. Using real data, the proposed methodology has also been compared with the K-means methodology in order to analyse its advantages and conditions of use. The results have demonstrated an improvement in accuracy and geometrical definition of the axis obtained. Numéro de notice : A2017-551 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1171956 En ligne : https://doi.org/10.1080/00396265.2016.1171956 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86612 [article]

Experiences with the QDaedalus system for astrogeodetic determination of deflections of the vertical / Markus Hauk in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 294 - 301 Titre : Experiences with the QDaedalus system for astrogeodetic determination of deflections of the vertical Type de document : Article/Communication Auteurs : Markus Hauk, Auteur ; C. Hirt, Auteur ; C. Ackermann, Auteur Année de publication : 2017 Article en page(s) : pp 294 - 301 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] astronomie de position [Termes IGN] Bavière (Allemagne) [Termes IGN] chambre zénithale [Termes IGN] champ de pesanteur local [Termes IGN] détecteur à transfert de charge [Termes IGN] déviation de la verticale [Termes IGN] tachéomètre Résumé : (Auteur) This paper explores the astrogeodetic deflection of the vertical (VD) determination with a light-weight tachymeter-based measurement system called ‘QDaedalus’ developed at ETH Zurich. A description of the relevant components of the system is given to show the set-up and operation. The measuring process including CCD-tachymeter calibration and the astronomical data processing are summarised. The paper then analyses the achievable accuracy of VDs based on new measurement data acquired in Bavaria over several nights. Our measurements were executed atop a pillar on the roof of the TUM and at six stations in the Bavarian Alps (Estergebirge) with highly accurate VDs from previous digital zenith camera measurements available. Our comparisons indicate an accuracy level of 0.15–0.20 arc-seconds for VDs measured with QDaedalus. As a conclusion, our results show that the QDaedalus system is a promising sensor for accurate local astronomical gravity field surveys when a zenith camera is not available. Numéro de notice : A2017-552 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1171960 En ligne : https://doi.org/10.1080/00396265.2016.1171960 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86613 [article]

Learning effectiveness of virtual environments for 3D terrain interpretation and data acquisition / A.M. Perez-Romero in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 302 - 311 Titre : Learning effectiveness of virtual environments for 3D terrain interpretation and data acquisition Type de document : Article/Communication Auteurs : A.M. Perez-Romero, Auteur ; M. Castro-Garcia, Auteur ; M.J. Leon-Bonillo, Auteur ; F. Manzano-Agugliaro, Auteur Année de publication : 2017 Article en page(s) : pp 302 - 311 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Formation [Termes IGN] données localisées 3D [Termes IGN] modèle physique [Termes IGN] monde virtuel Résumé : (Auteur) The aim of this study is to assess the effectiveness of different learning strategies for 3D terrain interpretation and data acquisition by engineering students. According to the experimental design, students received homogeneous training, followed by differential training, which divided the students into three statistically homogeneous groups where each group was subject to a different learning process: (1) virtual environment learning; (2) learning using physical scale models; and (3) a theoretical class. Afterwards, the students were evaluated using two tests under real field conditions. Results were obtained for the following study variables: field-test scores and whether or not the student was repeating the course. The students who learned using physical scale models obtained the best scores; their scores were significantly higher than those of students using virtual environment or a theoretical class. These findings open up new perspectives on the teaching of surveying with respect to other teaching methods. Numéro de notice : A2017-553 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1172814 En ligne : https://doi.org/10.1080/00396265.2016.1172814 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86614 [article]

Height uncertainty in digital terrain modelling with unmanned aircraft systems / Stig-Göran Mårtensson in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 312 - 318 Titre : Height uncertainty in digital terrain modelling with unmanned aircraft systems Type de document : Article/Communication Auteurs : Stig-Göran Mårtensson, Auteur ; Yuriy Reshetyuk, Auteur Année de publication : 2017 Article en page(s) : pp 312 - 318 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] Agisoft Photoscan [Termes IGN] altitude [Termes IGN] drone [Termes IGN] incertitude géométrique [Termes IGN] modèle numérique de surface [Termes IGN] modèle numérique de terrain [Termes IGN] surface imperméable Résumé : (Auteur) The purpose of this paper is to investigate the height uncertainty of digital terrain models (DTMs) generated from unmanned aircraft system (UAS) surveys over different surface types – asphalt, gravel and grass. The data used in the study was acquired during two UAS flights performed in spring 2014 with a fixed wing aircraft and two different cameras, from the flying height of about 100 m, and it was processed in different software suites – Agisoft PhotoScan, RapidStation and RapidTerrain. The results show that it is possible to achieve the height uncertainty (expressed as a Root Mean Square Error) in a DTM of below 0.02 m on asphalt surfaces and below 0.04 m on gravel and grass surfaces, provided an overcast sky. Numéro de notice : A2017-554 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/00396265.2016.1180754 En ligne : http://dx.doi.org/10.1080/00396265.2016.1180754 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86615 [article]