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Dépouillements
Ajouter le résultat dans votre panierA closed-form formula to calculate geometric dilution of precision (GDOP) for multi-GNSS constellations / Yunlong Teng in GPS solutions, vol 20 n° 3 (July 2016)
Titre : A closed-form formula to calculate geometric dilution of precision (GDOP) for multi-GNSS constellations Type de document : Article/Communication Auteurs : Yunlong Teng, Auteur ; Jinling Wang, Auteur Année de publication : 2016 Article en page(s) : pp 331 - 339 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] affaiblissement géométrique de la précision
[Termes IGN] constellation GNSS
[Termes IGN] fonction analytiqueRésumé : (Auteur) With the future global navigation satellite system (GNSS), the multi-GNSS constellations, which are composed of various single systems, will be the main navigation method in future. For the multi-GNSS constellations, the geometric dilution of precision (GDOP) is an important parameter used for satellite selection and the evaluation of positioning accuracy. However, the calculation of GDOP is a time-consuming and power-consuming task. Using Schur complement, we present a closed-form formula to calculate GDOP for multi-GNSS constellations. The formula can be applied to multi-GNSS constellations that include two, three or four different single systems. Furthermore, a closed-form formula for the case of exactly five satellites is also derived. Compared with the conventional numerical methods, the formula can reduce the amounts of multiplication and addition effectively. Numerical experiments validate the effectiveness and feasibility of the closed-form formula. Numéro de notice : A2016-628 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0440-x En ligne : http://dx.doi.org/10.1007/s10291-015-0440-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81831
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 331 - 339[article]
Titre : Assessment of vertical TEC mapping functions for space-based GNSS observations Type de document : Article/Communication Auteurs : Jiahao Zhong, Auteur ; Jiuhou Lei, Auteur ; Xiankang Dou, Auteur ; Xinan Yue, Auteur Année de publication : 2016 Article en page(s) : pp 353 - 362 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] centroïde
[Termes IGN] coordonnées GNSS
[Termes IGN] hauteur de la couche ionosphérique
[Termes IGN] ionosphère
[Termes IGN] orbite basse
[Termes IGN] teneur totale en électrons
[Termes IGN] teneur verticale totale en électronsRésumé : (Auteur) The mapping function is commonly used to convert slant to vertical total electron content (TEC) based on the assumption that the ionospheric electrons concentrate in a layer. The height of the layer is called ionospheric effective height (IEH) or shell height. The mapping function and IEH are generally well understood for ground-based global navigation satellite system (GNSS) observations, but they are rarely studied for the low earth orbit (LEO) satellite-based TEC conversion. This study is to examine the applicability of three mapping functions for LEO-based GNSS observations. Two IEH calculating methods, namely the centroid method based on the definition of the centroid and the integral method based on one half of the total integral, are discussed. It is found that the IEHs increase linearly with the orbit altitudes ranging from 400 to 1400 km. Model simulations are used to compare the vertical TEC converted by these mapping functions and the vertical TEC directly calculated by the model. Our results illustrate that the F&K (Foelsche and Kirchengast) geometric mapping function together with the IEH from the centroid method is more suitable for the LEO-based TEC conversion, though the thin layer model along with the IEH of the integral method is more appropriate for the ground-based vertical TEC retrieval. Numéro de notice : A2016-629 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0444-6 En ligne : http://dx.doi.org/10.1007/s10291-015-0444-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81832
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 353 - 362[article]
Titre : Identifying a low-frequency oscillation in Galileo IOV pseudorange rates Type de document : Article/Communication Auteurs : Daniele Borio, Auteur ; Ciro Gioia, Auteur ; Neil Mitchison, Auteur Année de publication : 2016 Article en page(s) : pp 363 - 372 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] étalonnage en vol
[Termes IGN] Galileo
[Termes IGN] horloge atomique
[Termes IGN] mesurage de pseudo-distance
[Termes IGN] oscillateur
[Termes IGN] performance
[Termes IGN] vitesseRésumé : (Auteur) Galileo, the European global navigation satellite system, is in its in-orbit validation phase and the four satellites which have been available for some months now have allowed a preliminary analysis of the system performance. Previous studies have showed that Galileo will be able to provide pseudorange measurements more accurate than those provided by GPS. However, a similar improvement was not found for pseudorange rate observations in the velocity domain. This fact stimulated additional analysis of the velocity domain, and, in particular, an unintended oscillatory component was identified as the main error source in the velocity solution. The magnitude of such oscillation is less than 10 cm/s, and its period is in the order of few minutes. A methodology was developed to identify oscillatory components in the Galileo IOV pseudorange rate observables, and it was verified that the measurements from Galileo IOV PFM and Galileo IOV FM2 are affected by a small oscillatory disturbance. This disturbance stems from the architecture adopted for combining the frequency references provided by the two active clocks present in the Galileo satellites. The issue has been solved in Galileo IOV FM3 and Galileo IOV FM4, and the oscillatory component has been eliminated. We also propose a methodology for removing this unwanted component from the final velocity solution and for determining the performance that Galileo will be able to achieve. The analysis shows that Galileo velocity solution will provide a root-mean-square error of about 8 cm/s even in the limited geometry conditions achieved using only four satellites. This shows the potential of Galileo also in the determination of user velocity. Numéro de notice : A2016-630 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0443-7 En ligne : http://dx.doi.org/10.1007/s10291-015-0443-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81833
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 363 - 372[article]
Titre : GNSS multipath detection using three-frequency signal-to-noise measurements Type de document : Article/Communication Auteurs : Philip R.R. Strode, Auteur ; Paul D. Groves, Auteur Année de publication : 2016 Article en page(s) : pp 399 - 412 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] correction du trajet multiple
[Termes IGN] diffraction
[Termes IGN] rapport signal sur bruit
[Termes IGN] récepteur GNSS
[Termes IGN] récepteur trifréquence
[Vedettes matières IGN] Traitement de données GNSSRésumé : (Auteur) A new technique for detecting GNSS multipath interference by comparing signal-to-noise (SNR) measurements on three frequencies is presented. Depending on the phase lag of the reflected signal with respect to the direct signal, multipath interference can be either constructive or destructive, with a commensurate effect on the measured SNR. However, as the phase lag is frequency dependent, the SNR is perturbed differently on each frequency. Thus, by differencing SNR measurements on different frequencies and comparing the result with that obtained in a low-multipath environment, multipath can be detected. Using three frequencies makes the process more robust. A three-frequency SNR-based multipath detector has been developed and calibrated using measurements from GPS Block IIF satellites in a low-multipath environment. The new detector has been tested in a range of urban environments and its multipath detection capability verified by showing that the MP observables oscillate when the new detection statistic is above a threshold value determined using data collected in a low-multipath environment. The new detector is also sensitive to diffraction. Numéro de notice : A2016-631 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0449-1 En ligne : http://dx.doi.org/10.1007/s10291-015-0449-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81834
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 399 - 412[article]
Titre : Benefits of the third frequency signal on cycle slip correction Type de document : Article/Communication Auteurs : Xiaohong Zhang, Auteur ; Pan Li, Auteur Année de publication : 2016 Article en page(s) : pp 451 - 460 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] compensation Lambda
[Termes IGN] constellation BeiDou
[Termes IGN] glissement de cycle
[Termes IGN] positionnement ponctuel précis
[Termes IGN] récepteur trifréquenceRésumé : (Auteur) Cycle slip detection and correction are important issues when carrier phase observations are used in high-precision GNSS data processing and have, therefore, been intensively investigated. Along with the GNSS modernization, the cycle slip correction (CSC) problem has been raised to deal with more signals from multi-frequencies. We extend the geometry-based approach by integrating time-differenced pseudorange and carrier phase observations to estimate the integer number of triple-frequency cycle slips together with the receiver clock offset, ionospheric delay variations and receiver displacements. The Least-squares AMBiguity Decorrelation Adjustment method can be employed. The benefit of the third frequency observation on the cycle slip estimate is first investigated with simulation tests. The results show that adding the third frequency observation can significantly improve the model strength and that a reliable triple-frequency CSC with a theoretical success rate of higher than 99.9 % can still be achieved, even under the condition that the range or ionosphere delay variation is poorly defined. The performance of triple-frequency CSC is validated with real triple-frequency BDS data since all BDS satellites in orbit are transmitting triple-frequency signals. The results show that the fixing rate of CSC can reach 99.1 % in static precise point positioning (PPP) and 98.8 % in the kinematic case. PPP solutions with cycle slip-uncorrected and cycle slip-corrected data sets are compared to validate the correctness of triple-frequency CSC. The standard deviations of the PPP solution in east, north and vertical component, respectively, can be improved by 31.1, 30.7 and 37.6 % for static, and by 42.0, 53.8 and 39.7 % for kinematic after cycle slips are corrected. The performance of dual- and triple-frequency CSC is also compared. Results show that the performance of dual-frequency CSC is slightly worse than that of triple-frequency CSC. These results demonstrate that the performance of CSC can be significantly improved with triple-frequency observations. Numéro de notice : A2016-632 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0456-2 En ligne : http://dx.doi.org/10.1007/s10291-015-0456-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81835
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 451 - 460[article]
Titre : Improved PPP performance in regional networks Type de document : Article/Communication Auteurs : Stefano Gandolfi, Auteur ; Luca Tavasci, Auteur ; Luca Poluzzi, Auteur Année de publication : 2016 Article en page(s) : pp 485 - 497 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] GIPSY-OASIS
[Termes IGN] International Terrestrial Reference System
[Termes IGN] positionnement ponctuel précis
[Termes IGN] réseau géodésique local
[Termes IGN] série temporelle
[Termes IGN] transformation de HelmertRésumé : (Auteur) It has been demonstrated that precise point positioning (PPP) is a powerful tool in geodetic and geodynamic applications. As is known, it provides solutions in the reference system of the satellite orbits. We focuses on the strategy to transform PPP solutions into the International Terrestrial Reference System (ITRS) by applying a set of local Helmert transformation parameters obtained from a regional network rather than using global parameters. In order to carry out this test, a regional network composed of 14 stations was analyzed using GIPSY-OASIS II software, over a period of 6 years. Two solutions differently aligned to the ITRS were compared in terms of accuracy, scattering, frequency content and local movements. One solution is aligned to IGb08 through the X-files provided by JPL, while the other is aligned to the European reference frame densification of IGb08 using customized regional X-files. Therefore, both are updated realizations of the ITRS. The test shows that a regional, instead of a global, alignment to the ITRS can significantly improve the repeatability of the solutions. A small improvement can also be found in terms of agreement with the regional densification of IGb08. The analysis of the signal content in the differently aligned time series allowed some differences to be found, in terms of both frequency and magnitude. These differences are mainly due to an evident common signal that is defined for the whole area and which is removed when using regional alignment. Finally, residual scattering was calculated after removing the modeled signals from each time series, which results in a scatter being significantly smaller for the regional solution than for the global solution. In order to obtain these results, the choice of the reference stations is a major question and therefore discussed in detail. Numéro de notice : A2016-633 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0459-z En ligne : http://dx.doi.org/10.1007/s10291-015-0459-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81836
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 485 - 497[article]
Titre : Performance of real-time Precise Point Positioning using IGS real-time service Type de document : Article/Communication Auteurs : Mohamed Elsobeiey, Auteur ; Salim Al-Harbi, Auteur Année de publication : 2016 Article en page(s) : pp 565 - 571 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] correction du signal
[Termes IGN] horloge
[Termes IGN] international GPS service for geodynamics
[Termes IGN] orbite
[Termes IGN] positionnement ponctuel précis
[Termes IGN] temps réelRésumé : (Auteur) Until recently, the real-time IGS precise orbit and clock corrections were only available for the predicted part of the ultra-rapid solution. Whereas the accuracy of the ultra-rapid orbit is about 5 cm, the root mean square (RMS) of the respective satellite clock corrections is, unfortunately, about 3 ns (0.9 m). Hence, high accuracy Precise Point Positioning (PPP) applications can be achieved only in post-processing rather than in realtime. With the availability of the IGS real-time service (RTS), it becomes possible to obtain precise satellite orbit and satellite clock corrections in realtime with accuracy better than those of the ultra-rapid products. Recent research has shown that GPS IGS RTS products availability is at least 95 %, which makes it possible to perform real-time PPP with high accuracy. We study the performance of IGS RTS products in PPP by introducing a detailed description and analysis of IGS RTS products, describing the broadcasting of the IGS RTS orbit and clock corrections and their implementation as corrections to the broadcast ephemerides, and analyzing IGS RTS in PPP using several, randomly selected globally distributed IGS stations. It is shown that using IGS RTS products in real-time PPP can improve the solution RMS by about 50 % compared with the solution obtained from the predicted part of the IGS ultra-rapid products. Numéro de notice : A2016-635 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0467-z En ligne : http://dx.doi.org/10.1007/s10291-015-0467-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81837
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 565 - 571[article]
Titre : A new method for specular and diffuse pseudorange multipath error extraction using wavelet analysis Type de document : Article/Communication Auteurs : Giovanni Pugliano, Auteur ; Umberto Robustelli, Auteur ; Fabio Rossi, Auteur ; Raffaele Santamaria, Auteur Année de publication : 2016 Article en page(s) : pp 499 - 508 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Campanie (Italie)
[Termes IGN] correction du trajet multiple
[Termes IGN] mesurage de pseudo-distance
[Termes IGN] onde porteuse
[Termes IGN] réflexion spéculaire
[Termes IGN] transformation en ondelettes
[Vedettes matières IGN] Traitement de données GNSSRésumé : (Auteur) Multipath remains one of the major challenges in Global Navigation Satellite System (GNSS) positioning because it is considered the dominant source of ranging errors, which can be classified into specular and diffuse types. We present a new method using wavelets to extract the pseudorange multipath in the time domain and breaking it down into the two components. The main idea is an analysis-reconstruction approach based on application of both continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The proposed procedure involves the use of L1 code-minus-carrier (CMC) observable where higher-frequency terms are isolated as residuals. CMC residuals are analyzed by applying the CWT, and we propose the scalogram as a technique for discerning time–frequency variations of the multipath signal. Unlike Fourier transform, the potential of the CWT scalogram for examining the non-stationary and multifrequency nature of the multipath is confirmed as it simultaneously allows fine detection and time localization of the most representative frequencies of the signal. This interpretation of the CWT scalogram is relevant when choosing the levels of reconstruction with DWT, allowing accurate time domain extraction of both the specular and diffuse multipath. The performance and robustness of the method and its boundary applicability are assessed. The experiment was carried out using a receiver of Campania GNSS Network. The results are given in which specular multipath error is achieved using DWT level 7 approximation component and diffuse multipath error is achieved using DWT level 6 denoised detail component. Numéro de notice : A2016-634 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0458-0 En ligne : http://dx.doi.org/10.1007/s10291-015-0458-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81838
in GPS solutions > vol 20 n° 3 (July 2016) . - pp 499 - 508[article]
