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Reducing multipath effect of low-cost GNSS receivers for monitoring by considering temporal correlations / Li Zhang in Journal of applied geodesy, vol 14 n° 2 (April 2020)  

Public [article]  inJournal of applied geodesy > vol 14 n° 2 (April 2020) . - pp 167 – 175 Titre : Reducing multipath effect of low-cost GNSS receivers for monitoring by considering temporal correlations Type de document : Article/Communication Auteurs : Li Zhang, Auteur ; Volker Schwieger, Auteur Année de publication : 2020 Article en page(s) : pp 167 – 175 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] atténuation du signal [Termes descripteurs IGN] corrélation temporelle [Termes descripteurs IGN] coût [Termes descripteurs IGN] itération [Termes descripteurs IGN] ligne de base [Termes descripteurs IGN] oscillation [Termes descripteurs IGN] phase [Termes descripteurs IGN] plan de masse [Termes descripteurs IGN] qualité des données [Termes descripteurs IGN] récepteur GNSS [Termes descripteurs IGN] récepteur monofréquence [Termes descripteurs IGN] réflecteur [Termes descripteurs IGN] source d'erreur [Termes descripteurs IGN] trajet multiple Résumé : (auteur) The investigations on low-cost single frequency GNSS receivers at the Institute of Engineering Geodesy (IIGS) show that u-blox GNSS receivers combined with low-cost antennas and self-constructed L1-optimized choke rings can reach an accuracy which almost meets the requirements of geodetic applications (see Zhang and Schwieger [25]). However, the quality (accuracy and reliability) of low-cost GNSS receiver data should still be improved, particularly in environments with obstructions. The multipath effects are a major error source for the short baselines. The ground plate or the choke ring ground plane can reduce the multipath signals from the horizontal reflector (e. g. ground). However, the shieldings cannot reduce the multipath signals from the vertical reflectors (e. g. walls). Because multipath effects are spatially and temporally correlated, an algorithm is developed for reducing the multipath effect by considering the spatial correlations of the adjoined stations (see Zhang and Schwieger [24]). In this paper, an algorithm based on the temporal correlations will be introduced. The developed algorithm is based on the periodic behavior of the estimated coordinates and not on carrier phase raw data, which is easy to use. Because, for the users, coordinates are more accessible than the raw data. The multipath effect can cause periodic oscillations but the periods change over time. Besides this, the multipath effect’s influence on the coordinates is a mixture of different multipath signals from different satellites and different reflectors. These two properties will be used to reduce the multipath effect. The algorithm runs in two steps and iteratively. Test measurements were carried out in a multipath intensive environment; the accuracies of the measurements are improved by about 50 % and the results can be delivered in near-real-time (in ca. 30 minutes), therefore the algorithm is suitable for structural health monitoring applications. Numéro de notice : A2020-217 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2019-0059 date de publication en ligne : 27/03/2020 En ligne : https://doi.org/10.1515/jag-2019-0059 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94910 [article]

Calibration errors in determining slant Total Electron Content (TEC) from multi-GNSS data / Wei Li in Advances in space research, vol 63 n° 5 (1 March 2019)  

Public [article]  inAdvances in space research > vol 63 n° 5 (1 March 2019) . - pp 1670 - 1680 Titre : Calibration errors in determining slant Total Electron Content (TEC) from multi-GNSS data Type de document : Article/Communication Auteurs : Wei Li, Auteur ; Guangxing Wang, Auteur ; Jinzhong Mi, Auteur ; Shaocheng Zhang, Auteur Année de publication : 2019 Article en page(s) : pp 1670 - 1680 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes descripteurs IGN] données BeiDou [Termes descripteurs IGN] données Galileo [Termes descripteurs IGN] données GNSS [Termes descripteurs IGN] données GPS [Termes descripteurs IGN] étalonnage des données [Termes descripteurs IGN] ligne de base [Termes descripteurs IGN] propagation ionosphérique [Termes descripteurs IGN] simple différence [Termes descripteurs IGN] teneur totale en électrons [Termes descripteurs IGN] trajet multiple Résumé : (Auteur) The global navigation satellite system (GNSS) is presently a powerful tool for sensing the Earth's ionosphere. For this purpose, the ionospheric measurements (IMs), which are by definition slant total electron content biased by satellite and receiver differential code biases (DCBs), need to be first extracted from GNSS data and then used as inputs for further ionospheric representations such as tomography. By using the customary phase-to-code leveling procedure, this research comparatively evaluates the calibration errors on experimental IMs obtained from three GNSS, namely the US Global Positioning System (GPS), the Chinese BeiDou Navigation Satellite System (BDS), and the European Galileo. On the basis of ten days of dual-frequency, triple-GNSS observations collected from eight co-located ground receivers that independently form short-baselines and zero-baselines, the IMs are determined for each receiver for all tracked satellites and then for each satellite differenced for each baseline to evaluate their calibration errors. As first derived from the short-baseline analysis, the effects of calibration errors on IMs range, in total electron content units, from 1.58 to 2.16, 0.70 to 1.87, and 1.13 to 1.56 for GPS, Galileo, and BDS, respectively. Additionally, for short-baseline experiment, it is shown that the code multipath effect accounts for their main budget. Sidereal periodicity is found in single-differenced (SD) IMs for GPS and BDS geostationary satellites, and the correlation of SD IMs over two consecutive days achieves the maximum value when the time tag is around 4 min. Moreover, as byproducts of zero-baseline analysis, daily between-receiver DCBs for GPS are subject to more significant intra-day variations than those for BDS and Galileo. Numéro de notice : A2019-172 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2018.11.020 date de publication en ligne : 05/12/2018 En ligne : https://doi.org/10.1016/j.asr.2018.11.020 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92624 [article]

Optimisation of GNSS networks, considering baseline correlations / M. Amin Alizadeh-Khameneh in Survey review, vol 51 n° 364 (January 2019)  

Public [article]  inSurvey review > vol 51 n° 364 (January 2019) . - pp 35 - 42 Titre : Optimisation of GNSS networks, considering baseline correlations Type de document : Article/Communication Auteurs : M. Amin Alizadeh-Khameneh, Auteur ; Lars E. Sjöberg, Auteur ; Anna B. O. Jensen, Auteur Année de publication : 2019 Article en page(s) : pp 35 - 42 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes descripteurs IGN] corrélation [Termes descripteurs IGN] données GNSS [Termes descripteurs IGN] double différence [Termes descripteurs IGN] ligne de base [Termes descripteurs IGN] optimisation (mathématiques) [Termes descripteurs IGN] réseau géodésique local [Termes descripteurs IGN] Suède Résumé : (Auteur) By considering global navigation satellite system (GNSS) observations, one can perform optimisation according to some pre-defined criteria and come up with the best location of receivers and optimum number of baselines. In practice, it is quite common to neglect the effect of correlations between baselines, and instead assume single-baseline-adjusted data in the optimisation procedure. However, in each session of observation, usually more than two receivers are simultaneously taking data from a number of common GNSS satellites, implying that the single- or double-difference observations are correlated. Our study designs an optimal observation plan for a GPS network in Skåne in southern Sweden, with the aim of determining possible displacements. Assuming three receivers in each session of observations leads to correlation between the GPS baselines, and consequently a fully populated weight matrix for each session of observation. A bi-objective optimisation model of precision and reliability is chosen to optimise the variance factor of each session, and eventually, design an observation plan. It is shown in this study that observing six out of ten possible sessions is sufficient to enable the network to detect a 5 mm displacement at each station. Assuming that the double-difference phase observations are uncorrelated changes the observation plan by retaining two more sessions. However, defining the weight matrix based on the double-difference observations requires the correlations to be taken into account, and neglecting them leads to incorrect results. Numéro de notice : A2019-187 Thématique : POSITIONNEMENT Nature : Numéro de périodique nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2017.1342896 date de publication en ligne : 26/06/2017 En ligne : https://doi.org/10.1080/00396265.2017.1342896 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92618 [article]

RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications / Francesco Darugna (2019)

Public Titre : RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications Type de document : Article/Communication Auteurs : Francesco Darugna, Auteur ; et al., Auteur Congrès : ION GNSS+ 2019, 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (septembre 2019; Miami, Floride - Etats-Unis), Commanditaire Editeur : Alexandria : Institute of Navigation Année de publication : 2019 Importance : pp 3932 - 3945 Format : 21 x 30 cm Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] bruit atmosphérique [Termes descripteurs IGN] correction du trajet multiple [Termes descripteurs IGN] ligne de base [Termes descripteurs IGN] positionnement cinématique en temps réel [Termes descripteurs IGN] positionnement ponctuel précis [Termes descripteurs IGN] précision centimétrique [Termes descripteurs IGN] téléphone intelligent [Termes descripteurs IGN] trajet multiple Résumé : (auteur) Low cost receivers providing GNSS code and phase raw measurements for multiple frequencies and multiple GNSS constellations have recently become available on the market. This significantly increases the number of devices equipped with the necessary sensors to perform precise GNSS positioning like Network-RTK or PPP. The smartphone GNSS measurements often suffer from low signal-to-noise, inhomogeneous antenna gain and high levels of multipath. Here, we show how to tackle several of currently present obstacles and demonstrate centimeter-level kinematic positioning with a low-cost GNSS antenna and a low-cost GNSS receiver built into an off-the-shelf smartphone. For some devices we found that the phase observations do not have integer characteristic but appear to have random biases. To some extend these observations can still be used in a “float”-type precise algorithm. Low cost GNSS sensors like the ones built into smartphones are generally used with antennas that have a uniform gain pattern and do not reject LHCP signals. Accordingly, strong multipath influence is observed in many applications. Experiments both in a zero-baseline and a short-baseline configuration have been performed, to evaluate the aforementioned biases and discontinuities. We demonstrate instantaneous ambiguity resolution in the zero-baseline setup, showing the potential for RTK-positioning with low-cost sensors available inside smartphones. Positioning with PPP-RTK or Network-RTK is more challenging because additional residual atmospheric noise is present. Experiments with different baseline lengths have been performed in different ionospheric conditions and the achieved accuracies are reported. Numéro de notice : C2019-040 Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95376

Assessment of local GNSS baselines at co-location sites / Iván Herrera Pinzón in Journal of geodesy, vol 92 n° 9 (September 2018)  

Public [article]  inJournal of geodesy > vol 92 n° 9 (September 2018) . - pp 1079 - 1095 Titre : Assessment of local GNSS baselines at co-location sites Type de document : Article/Communication Auteurs : Iván Herrera Pinzón, Auteur ; Markus Rothacher, Auteur Année de publication : 2018 Article en page(s) : pp 1079 - 1095 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes descripteurs IGN] co-positionnement [Termes descripteurs IGN] erreur systématique [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] ligne de base [Termes descripteurs IGN] point de liaison (géodésie) [Termes descripteurs IGN] positionnement par GNSS [Termes descripteurs IGN] retard troposphérique zénithal [Termes descripteurs IGN] série temporelle [Termes descripteurs IGN] station permanente Résumé : (Auteur) As one of the major contributors to the realisation of the International Terrestrial Reference System (ITRS), the Global Navigation Satellite Systems (GNSS) are prone to suffer from irregularities and discontinuities in time series. While often associated with hardware/software changes and the influence of the local environment, these discrepancies constitute a major threat for ITRS realisations. Co-located GNSS at fundamental sites, with two or more available instruments, provide the opportunity to mitigate their influence while improving the accuracy of estimated positions by examining data breaks, local biases, deformations, time-dependent variations and the comparison of GNSS baselines with existing local tie measurements. With the use of co-located GNSS data from a subset sites of the International GNSS Service network, this paper discusses a global multi-year analysis with the aim of delivering homogeneous time series of coordinates to analyse system-specific error sources in the local baselines. Results based on the comparison of different GNSS-based solutions with the local survey ties show discrepancies of up to 10 mm despite GNSS coordinate repeatabilities at the sub-mm level. The discrepancies are especially large for the solutions using the ionosphere-free linear combination and estimating tropospheric zenith delays, thus corresponding to the processing strategy used for global solutions. Snow on the antennas causes further problems and seasonal variations of the station coordinates. These demonstrate the need for a permanent high-quality monitoring of the effects present in the short GNSS baselines at fundamental sites. Numéro de notice : A2018-459 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1108-9 date de publication en ligne : 17/01/2018 En ligne : https://doi.org/10.1007/s00190-017-1108-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91056 [article]

Amélioration des calculs GNSS à façon du SGN / Mathilde Kremp (2018) 

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Baseline and triangulation geometry in a standard plenoptic camera / Christopher Hahne in International journal of computer vision, vol 126 n° 1 (January 2018)  

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Bounding the integer bootstrapped GNSS baseline’s tail probability in the presence of stochastic uncertainty / Steven E. Langel in Journal of geodesy, vol 90 n° 11 (November 2016)  

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New data processing strategy for single frequency GPS deformation monitoring / S-Q. Huang in Survey review, vol 47 n° 344 (September 2015)  

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

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Fusion of camera images and laser scans for wide baseline 3D scene alignment in urban environments / Michael Ying Yang in ISPRS Journal of photogrammetry and remote sensing, vol 66 n° 6 supplement (December 2011)  

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Asymmetric tropospheric delays from numerical weather models for UT1 determination from VLBI Intensive sessions on the baseline Wettzell–Tsukuba / Johannes Böhm in Journal of geodesy, vol 84 n° 5 (May 2010)  

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Real-time adjustment underwater positioning system for submarines / W. Cheng in Marine geodesy, vol 33 n° 2-3 (April - September 2010)  

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Interference measurements of the Nummela standard baseline in 2005 and 2007 / J. Jokela (2010)    

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A new methodology for measuring coastline recession using buffering and non-linear least squares estimation / J. Heo in International journal of geographical information science IJGIS, vol 23 n°9-10 (september 2009)

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