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An accurate train positioning method using tightly-coupled GPS + BDS PPP/IMU strategy / Wei Jiang in GPS solutions, vol 26 n° 3 (July 2022)  

Public [article]  inGPS solutions > vol 26 n° 3 (July 2022) . - n° 67 Titre : An accurate train positioning method using tightly-coupled GPS + BDS PPP/IMU strategy Type de document : Article/Communication Auteurs : Wei Jiang, Auteur ; Mengyang Liu, Auteur ; Baigen Cai, Auteur Année de publication : 2022 Article en page(s) : n° 67 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] Chine [Termes IGN] filtre de Kalman [Termes IGN] phase [Termes IGN] positionnement inertiel [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] signal GPS [Termes IGN] simple différence [Termes IGN] train Résumé : (auteur) A new GNSS/IMU tightly coupled positioning system is introduced to train positioning. To fulfil a train control system’s aim of reducing the need to install trackside equipment, the GNSS precise point positioning (PPP) method is applied in place of the conventional differential GNSS method. As the railway environment has the character of long operational mileage and complex GNSS measurement conditions, the GPS and BDS constellations are combined with measurement processing to improve the system’s continuity and stability. Ultra-rapid GNSS orbit and clock product is used for real-time PPP. The GNSS-PPP and IMU are tightly coupled using an Extended Kalman filter with single-differenced ionospheric-free GPS + BDS carrier phase and pseudorange observations. The carrier phase ambiguities are estimated as “float” values every epoch to reduce the impact of GNSS signal loss-of-lock and cycle slips. A train experiment was conducted on the Qinghai-Tibet Railway to evaluate system performance. The results show that the proposed system has a better performance than the conventional methods, including GPS + BDS PPP, LC GPS + BDS PPP/IMU and TC GPS PPP/IMU, with 52.1%, 49.4% and 52.1%, respectively. The tightly-coupled GPS + BDS PPP/IMU system under conditions of partly blocked GNSS coverage was evaluated to evaluate the system's continuity. It was confirmed that the proposed system had more stable positioning results and higher positioning accuracy. Numéro de notice : A2022-361 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-022-01250-2 Date de publication en ligne : 08/04/2022 En ligne : https://doi.org/10.1007/s10291-022-01250-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100580 [article]

GNSS carrier phase time-variant observable-specific signal bias (OSB) handling: an absolute bias perspective in multi-frequency PPP / Ke Su in GPS solutions, vol 26 n° 3 (July 2022)  

Public [article]  inGPS solutions > vol 26 n° 3 (July 2022) . - n° 71 Titre : GNSS carrier phase time-variant observable-specific signal bias (OSB) handling: an absolute bias perspective in multi-frequency PPP Type de document : Article/Communication Auteurs : Ke Su, Auteur ; Shuanggen Jin, Auteur ; Guoqiang Jiao, Auteur Année de publication : 2022 Article en page(s) : n° 71 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur de phase [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] signal BeiDou [Termes IGN] signal Galileo [Termes IGN] temps de convergence Résumé : (auteur) In precise satellite clock estimation, the satellite clock offsets absorb the pseudorange and carrier phase time-variant hardware delays. The dissimilarity of the satellite clock estimated with observations at different frequencies is termed the inter-frequency clock bias (IFCB). The bias inconsistency suggests that the simple ionospheric-free satellite clock cannot directly be applied to the multi-frequency carrier phase observations in multi-frequency precise point positioning (PPP). We propose the carrier phase time-variant observable-specific signal bias (OSB) concept and the corresponding estimation approach to solve this. The definition, rationality, reliability and validity of the carrier phase time-variant OSB are clarified. The new concept advantage is that a set of the carrier phase time-variant OSB values can directly amend on the carrier phase observations, and thereafter, the IFCB effect can be eliminated, which provides the flexibilities for the GNSS carrier phase observation handing. Datasets collected from 144 Multi-GNSS Experiment (MGEX) stations are adopted for the carrier phase time-variant OSB estimation and an analysis of its effect on the GNSS multi-frequency PPP performance. The various multi-frequency PPP models are tested and evaluated considering the carrier phase time-variant OSB correction. The results indicate that the GPS, BDS-2 and BDS-3 carrier phase time-variant OSB time series have the obvious amplitudes and the amplitudes of the Galileo and QZSS carrier phase time-variant OSB are small. The GPS and BDS-2 multi-frequency PPP performance is significantly enhanced when correcting the carrier phase time-variant OSB. The GPS-only kinematic ionospheric-float PPP exhibits the positioning accuracy of 1.0 cm, 2.2 cm and 2.6 cm in the north, east and up components when correcting the carrier phase time-variant OSB, whereas the positioning accuracy of the case without the correction is 1.4 cm, 2.8 cm and 3.7 cm in three directions, respectively. The mean convergence time of two dual-frequency and three triple-frequency BDS-2-only kinematic PPP is reduced by 5.0%, 4.9%, 5.4%, 4.7% and 4.6%, respectively, with the carrier phase time-variant OSB correction. The carrier phase time-variant OSB improvement on BDS-3-only multi-frequency PPP is not obvious owing to the relatively few available and stable carrier phase time-variant OSB values. The reliability, suitability and effectiveness of the GNSS carrier phase time-variant OSB are demonstrated. Numéro de notice : A2022-360 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01255-x Date de publication en ligne : 22/04/2022 En ligne : https://doi.org/10.1007/s10291-022-01255-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100579 [article]

Multi-frequency phase-only PPP-RTK model applied to BeiDou data / Pengyu Hou in GPS solutions, vol 26 n° 3 (July 2022)  

Public [article]  inGPS solutions > vol 26 n° 3 (July 2022) . - n° 76 Titre : Multi-frequency phase-only PPP-RTK model applied to BeiDou data Type de document : Article/Communication Auteurs : Pengyu Hou, Auteur ; Baocheng Zhang, Auteur ; Yury V. Yasyukevich, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 76 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] données BeiDou [Termes IGN] erreur de phase [Termes IGN] fréquence multiple [Termes IGN] modèle de simulation [Termes IGN] phase GNSS [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] retard ionosphèrique [Termes IGN] trajet multiple Résumé : (auteur) Typically, navigation software processes global navigation satellite system (GNSS) phase observables along with the code observables to achieve high-precision positioning. However, the unmodeled code-related errors, typically multipath effects, may deteriorate the positioning performance. Such effects are well known for the second generation BeiDou navigation satellite system (BDS-2). To prevent this adverse effect on the state-of-the-art positioning technique, namely integer ambiguity resolution-enabled precise point positioning (PPP-RTK), we propose a multi-frequency phase-only PPP-RTK model. This model excludes the code observables and addresses the rank deficiency problem underlying the phase observation equations at the undifferenced and uncombined level. To verify the model, we collect five-day triple-frequency BDS 30-s data from a network of seven reference stations (about 112 km apart) to estimate the products on the network side. Based on these products, we conduct simulated dynamic positioning at a user station to test the phase-only PPP-RTK model and compare it with the customary code-plus-phase (CPP) model. The results show that the satellite phase biases, existing only at the third frequency, have a precision of better than two centimeters, while the precision of the satellite clock and ionospheric delay is better than eight centimeters. Due to the strong correlation between individual corrections, it is necessary to assess the quality of combined products, including the satellite clock, satellite phase bias and ionospheric delay, the precision of which is several millimeters to two centimeters, which is sufficiently precise for user positioning. Regarding BDS-2 positioning, the time-to-first-fix (TTFF) of the CPP PPP-RTK is 12 epochs, while it is only three epochs for the phase-only PPP-RTK. The reason why the CPP model underperforms the phase-only model is that the BDS-2 data collected are subject to notable code multipath. We show that the code multipath in the third-generation BDS (BDS-3) data is mild, so the CPP PPP-RTK achieves instantaneous centimeter-level positioning with a TTFF of one epoch. The BDS-3 phase-only PPP-RTK obtains virtually the same positioning results, but the TTFF is two epochs. When combining BDS-2 with BDS-3, the TTFF of both models remains unchanged compared to that of the BDS-3 solutions, implying that ambiguity resolution based on the stronger dual-system CPP model is robust to the BDS-2 code multipath. However, the ambiguity-float solution of the CPP PPP-RTK is adversely affected by the code multipath and requires 43 epochs to convergence, while its phase-only counterpart needs 36 epochs. Numéro de notice : A2022-377 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-022-01263-x Date de publication en ligne : 10/05/2022 En ligne : https://doi.org/10.1007/s10291-022-01263-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100637 [article]

Outliers and uncertainties in GNSS ZTD estimates from double-difference processing and precise point positioning / Katarzyna Stępniak in GPS solutions, vol 26 n° 3 (July 2022)  

Public [article]  inGPS solutions > vol 26 n° 3 (July 2022) . - n° 74 Titre : Outliers and uncertainties in GNSS ZTD estimates from double-difference processing and precise point positioning Type de document : Article/Communication Auteurs : Katarzyna Stępniak, Auteur ; Olivier Bock , Auteur ; Pierre Bosser , Auteur ; Pawel Wielgosz, Auteur Année de publication : 2022 Projets : VEGAN / Bock, Olivier Article en page(s) : n° 74 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] données GNSS [Termes IGN] double différence [Termes IGN] ERA5 [Termes IGN] incertitude des données [Termes IGN] positionnement ponctuel précis [Termes IGN] retard troposphérique zénithal [Termes IGN] valeur aberrante [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Double-difference (DD) analysis and precise point positioning (PPP) are two widely used processing approaches to analyze ground-based GNSS measurements. We investigate the quality of the zenith tropospheric delay (ZTD) estimates produced from both processing approaches for a regional network over 1 year and show that DD solutions contain more numerous and larger ZTD outliers. The accuracy of both DD and PPP solutions strongly depends on the data processing procedure and models. We analyze the impact of mapping functions, satellite orbit and clock products and ambiguity resolution (fixed vs. float) on ZTD estimates. The results are assessed from station position repeatability and ZTD differences with respect to the ERA5 reanalysis. As expected, mapping functions have the strongest impact, with VMF1 being more accurate than GMF. Surprisingly, the impact of the ambiguity resolution and satellite products is rather weak in the PPP solution. We speculate that this results from the fact that final satellite products have reached a high level of accuracy and that other error sources now dominate static PPP solutions. A time and frequency analysis reveal unprecedented spurious sub-daily signals in the ZTD time series, which occur at the frequency of the GPS satellite repeat period and its harmonics. This suggests that sub-daily GPS ZTD estimates contain a significant part of the residual modeling errors due to satellite orbits, tidal models, mapping functions and multipath, which still need to be improved. Numéro de notice : A2022-359 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01261-z Date de publication en ligne : 29/04/2022 En ligne : https://doi.org/10.1007/s10291-022-01261-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100578 [article]

Assessing the positioning performance of GNSS receivers under different geomagnetic storm conditions / Chao Yan in Survey review, vol 54 n° 384 (May 2022)  

Public [article]  inSurvey review > vol 54 n° 384 (May 2022) . - pp 254 - 262 Titre : Assessing the positioning performance of GNSS receivers under different geomagnetic storm conditions Type de document : Article/Communication Auteurs : Chao Yan, Auteur ; Qing Wang, Auteur ; Bo Zhang, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : pp 254 - 262 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] glissement de cycle [Termes IGN] perturbation ionosphérique [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur GNSS [Termes IGN] signal GNSS [Termes IGN] tempête magnétique Résumé : (auteur) GNSS signals are affected when solar activity causes sudden variations in the density of the ionosphere. Few studies concentrate on positioning performance of IGS stations using different GNSS receivers under different geomagnetic storm conditions. This paper for the first time presents IF and UC PPP positioning performance of stations with different receivers during the quiet, moderate, intense, and super storms period. Firstly, a comprehensive investigation of geomagnetic storms effects on the occurrence of GPS cycle-slip and PPP positioning performance have been presented. Secondly, the influences of geomagnetic storms on the occurrence of cycle-slip and IF PPP positioning performance for stations using receivers provided by ‘JAVAD’, ‘LEICA’, and ‘TRIMBLE’ manufacturers have been comprehensively studied. Finally, this study investigates the geomagnetic storms effects on IF PPP positioning performance of stations using receiver types ‘JAVAD TRE_G3TH DELTA’, ‘JAVAD TRE_3 DELTA’, ‘LEICA GR25’, and ‘TRIMBLE NETR9’ by analysing observed data collected at mid-latitude region. Numéro de notice : A2022-356 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2021.1924967 Date de publication en ligne : 13/05/2021 En ligne : https://doi.org/10.1080/00396265.2021.1924967 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100555 [article]

A novel ionospheric mapping function modeling at regional scale using empirical orthogonal functions and GNSS data / Peng Chen in Journal of geodesy, vol 96 n° 5 (May 2022)  

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An improved vertical correction method for the inter-comparison and inter-validation of Integrated Water Vapour measurements / Olivier Bock in Atmospheric measurement techniques, vol 15 n° inconnu ([01/04/2022])  

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Assessment of RTK quadcopter and structure-from-motion photogrammetry for fine-scale monitoring of coastal topographic complexity / Stéphane Bertin in Remote sensing, vol 14 n° 7 (April-1 2022)  

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Characteristics of the BDS-3 multipath effect and mitigation methods using precise point positioning / Ran Lu in GPS solutions, vol 26 n° 2 (April 2022)  

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Coastal observation of sea surface tide and wave height using opportunity signal from Beidou GEO satellites: analysis and evaluation / Feng Wang in Journal of geodesy, vol 96 n° 4 (April 2022)  

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Detection and mitigation of GNSS spoofing via the pseudorange difference between epochs in a multicorrelator receiver / Xiangyong Shang in GPS solutions, vol 26 n° 2 (April 2022)  

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Regularized integer least-squares estimation: Tikhonov’s regularization in a weak GNSS model / Zemin Wu in Journal of geodesy, vol 96 n° 4 (April 2022)  

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Assessing ZWD models in delay and height domains using data from stations in different climate regions / Thainara Munhoz Alexandre de Lima in Applied geomatics, vol 14 n° 1 (March 2022)  

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Challenges related to the determination of altitudes of mountain peaks presented on cartographic sources / Katarzyna Chwedczuk in Geodetski vestnik, vol 66 n° 1 (March 2022)  

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Estimation of the height datum geopotential value of Hong Kong using the combined Global Geopotential Models and GNSS/levelling data / Panpan Zhang in Survey review, vol 54 n° 383 (March 2022)  

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