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Multipath mitigation for improving GPS narrow-lane uncalibrated phase delay estimation and speeding up PPP ambiguity resolution / Kai Zheng in Measurement, vol 206 (January 2023)  

Public [article]  inMeasurement > vol 206 (January 2023) . - n° 112243 Titre : Multipath mitigation for improving GPS narrow-lane uncalibrated phase delay estimation and speeding up PPP ambiguity resolution Type de document : Article/Communication Auteurs : Kai Zheng, Auteur ; Lingmin Tan, Auteur ; Kezhong Liu, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 112243 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse en composantes principales [Termes IGN] atténuation [Termes IGN] correction du trajet multiple [Termes IGN] mesurage de pseudo-distance [Termes IGN] phase GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] temps de convergence [Termes IGN] trajet multiple Résumé : (auteur) Precise point positioning (PPP) has been recognized as a powerful tool for various geophysical applications. However, the long convergence time required to resolve a reliable ambiguity impedes its further application in time-critical scenarios. Although PPP ambiguity resolution (AR) can shorten the convergence time, its performance is subject to the quality of float ambiguity estimates and the uncalibrated phase delay (UPD), which can be contaminated by multipath errors. Furthermore, the observation residuals derived from PPP are very likely to be affected by the common-mode error (CME), thereby deteriorating the multipath modeling accuracy. The principal component analysis (PCA) is employed to mitigate the CME effect, and the multipath is modeled using a multipath hemispherical map (MHM). Consequently, the narrow-lane (NL) UPDs with multipath correction have better temporal stability and residual distributions than those without correction. Compared with sidereal filtering (SF), the MHM0.5 has comparable residual variance reduction percentages, indicating its capability of capturing high-frequency multipath. For static PPP AR, the averaged time to first fix (TTFF) can be reduced by 24.2% to about 26 min and the convergence time can be achieved within 16.2 min after multipath correction. The pseudorange multipath correction significantly contributes to shortening the TTFF and convergence time. Reducing the resolution of MHM increases the risk of extending the TTFF. For kinematic PPP AR with MHM0.5, the convergence time exhibits a remarkable improvement when compared with that of the uncorrected case (21.7 min versus 40.2 min), and 20% of the stations achieve convergence within 10 min. Meanwhile, a few stations only take one minute to achieve convergence. The contribution of the multipath correction to the fixing rate is comparatively small. After applying MHM0.5, the kinematic positioning accuracies are improved by 35.7%, 12.6%, and 24.4% to 1.26, 1.39, and 2.73 cm for the east, north, and up components, respectively. Numéro de notice : A2023-027 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1016/j.measurement.2022.112243 Date de publication en ligne : 24/11/2022 En ligne : https://doi.org/10.1016/j.measurement.2022.112243 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102267 [article]

GNSS observable-specific phase biases for all-frequency PPP ambiguity resolution / Jianghui Geng in Journal of geodesy, vol 96 n° 2 (February 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 2 (February 2022) . - n° 11 Titre : GNSS observable-specific phase biases for all-frequency PPP ambiguity resolution Type de document : Article/Communication Auteurs : Jianghui Geng, Auteur ; Qiang Wen, Auteur ; Qiyuan Zhang, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 11 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] données Galileo [Termes IGN] erreur de phase [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] fréquence multiple [Termes IGN] horloge du satellite [Termes IGN] phase GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] signal GNSS [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) An unwritten rule to resolve GNSS ambiguities in precise point positioning (PPP-AR) is that users should follow faithfully the frequency choices and observable combinations mandated by satellite clock and phase bias providers. Switching to other frequencies of measurements requires that the satellite clocks be converted, albeit in a roundabout way, to agree with the new frequencies of code biases. Satellite phase biases, on the other hand, are prescribed conventionally as wide-lane and narrow-lane combinations, which prevents users from resolving other phase combinations in the case of multi-frequency observables. We therefore develop an approach to compute observable-specific phase biases (phase OSBs) in concert with the legacy, but ambiguity-fixed, satellite clocks to enable PPP-AR over any frequency choices and observable combinations at the user end, i.e., all-frequency PPP-AR. In particular, the phase OSBs on the baseline frequencies (e.g., L1/L2 for GPS and E1/E5a for Galileo) are estimated by decoupling the code OSBs pre-aligned with the satellite clocks; then satellite clocks are re-estimated by holding pre-resolved undifferenced ambiguities and phase OSBs on the baseline frequencies; finally, all third-frequency phase OSBs are determined by introducing the ambiguity-fixed satellite clocks above. We used a global network of multi-frequency GPS/Galileo data over a month to verify this approach. In dual-frequency PPP-AR using GPS L1/L2, L1/L5, Galileo E1/E5a, E1/E5b, E1/E5 and E1/E6 signals, over 95% of wide-lane and narrow-lane ambiguity residuals were within ±0.25 and ±0.15 cycles, respectively, after the code and phase OSB corrections on raw GNSS measurements. As a result, the ambiguity fixing rates reached around 95% in all PPP-AR tests, though it was only the satellite clocks aligned with the GPS L1/L2 and Galileo E1/E5a pseudorange that were applied throughout. We stress that the key to computing such phase OSBs for all-frequency PPP-AR is that the code OSBs have the same bias datum as that of the satellite clocks. Numéro de notice : A2022-135 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01602-3 Date de publication en ligne : 04/02/2022 En ligne : https://doi.org/10.1007/s00190-022-01602-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99740 [article]

Estimation and analysis of GPS inter-fequency clock biases from long-term triple-frequency observations / Fan Zhang in GPS solutions, vol 25 n° 4 (October 2021)  

Public [article]  inGPS solutions > vol 25 n° 4 (October 2021) . - n° 126 Titre : Estimation and analysis of GPS inter-fequency clock biases from long-term triple-frequency observations Type de document : Article/Communication Auteurs : Fan Zhang, Auteur ; Hongzhou Chai, Auteur ; Linyang Li, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 126 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] décalage d'horloge [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] fréquence multiple [Termes IGN] phase GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] station GNSS [Termes IGN] triple différence [Termes IGN] variation temporelle Résumé : (auteur) Usually, the difference between the satellite clocks computed with L1/L2 and clocks computed with L1/L5 is defined as inter-frequency clock bias (IFCB). It is critical to correct its L5 time-variant portion in the GNSS triple-frequency precise positioning. Using two years of observations from more than 100 stations worldwide, we use the epoch-differenced method to estimate IFCB for all available 12 GPS BLOCK-IIF satellites, and analyze its short-term and long-term variations. The experimental results indicate that the IFCB variations are clearly consistent for two satellites located in the same orbital plane, which perhaps means that the variations of IFCB are dependent on the orbital plane. We found that the IFCB of each Block-IIF satellite shows repetition characteristics over two years. The annual repetition cycle of 352 days of IFCB is consistent with the GPS year 351.4 days may originate from the rotation of satellites around the earth. GPS triple-frequency uncombined PPP is carried out using 9 globally distributed MGEX stations from June 1 to 30, 2018. The experimental results indicate that compared to the PPP solutions without IFCB corrections, GPS triple-frequency PPP can achieve an accuracy of 2.2, 3.8 and 11.4 mm in the north, east, and up components after correcting IFCB, which is an accuracy increase in 31.3%, 17.4%, and 13.0%, respectively. The average RMS of the phase posteriori residuals for each frequency is also reduced significantly, especially 79.1% for L5 frequency. Numéro de notice : A2021-565 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-021-01161-8 Date de publication en ligne : 10/07/2021 En ligne : https://doi.org/10.1007/s10291-021-01161-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98134 [article]

Impact of GPS processing on the estimation of snow water equivalent using refracted GPS signals / Ladina Steiner in IEEE Transactions on geoscience and remote sensing, vol 58 n° 1 (January 2020)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 58 n° 1 (January 2020) . - pp 123 - 135 Titre : Impact of GPS processing on the estimation of snow water equivalent using refracted GPS signals Type de document : Article/Communication Auteurs : Ladina Steiner, Auteur ; Michael Meindl, Auteur ; Christoph Marty, Auteur ; Alain Geiger, Auteur Année de publication : 2020 Article en page(s) : pp 123 - 135 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] Alpes [Termes IGN] altitude [Termes IGN] antenne GPS [Termes IGN] eau de fonte [Termes IGN] étalonnage des données [Termes IGN] manteau neigeux [Termes IGN] modèle hydrographique [Termes IGN] neige [Termes IGN] phase GPS [Termes IGN] pondération [Termes IGN] réfraction [Termes IGN] signal GPS [Termes IGN] Suisse Résumé : (auteur) Global navigation satellite system (GNSS) antennas buried underneath a snowpack have a high potential for in situ snow water equivalent (SWE) estimation. Automated and continuous SWE quantification independent of weather conditions could enhance snow hydrological monitoring and modeling. Accurate and reliable in situ data are needed for the calibration and validation of remote sensing data and snowpack modeling. A relative bias of less than 5% is achieved using sub-snow global positioning system (GPS) antennas (GPS refractometry) during a three full seasons time period in the Swiss Alps. A systematic overview regarding the temporal reliability of the sub-snow GPS derived results is, however, missing for this emerging technique. Moreover, GPS processing impacts the results significantly. Different GPS processing parameters are therefore selected and their influence on the SWE estimation is investigated. The impact of elevation-dependent weighting, the elevation cutoff angles, and the time intervals for SWE estimation are systematically assessed. The best results are achieved using all observations with an elevation-dependent weighting scheme. Moreover, the SWE estimation performance is equally accurate for hourly SWE estimation as for lower temporal resolutions up to daily estimates. The impact of snow on the coordinate solution is furthermore evaluated. While the east and north components are not systematically influenced by the overlying snowpack, the vertical component exhibits a significant variation and strongly depends on the SWE. The biased vertical component therefore provides an additional possibility to estimate SWE. Numéro de notice : A2020-074 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2019.2934016 Date de publication en ligne : 06/09/2019 En ligne : https://doi.org/10.1109/TGRS.2019.2934016 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94605 [article]

GPS receiver phase biases estimable in PPP-RTK networks : dynamic characterization and impact analysis / Baocheng Zhang in Journal of geodesy, vol 92 n° 6 (June 2018)  

Public [article]  inJournal of geodesy > vol 92 n° 6 (June 2018) . - pp 659 – 674 Titre : GPS receiver phase biases estimable in PPP-RTK networks : dynamic characterization and impact analysis Type de document : Article/Communication Auteurs : Baocheng Zhang, Auteur ; Teng Liu, Auteur ; Yunbin Yuan, Auteur Année de publication : 2018 Article en page(s) : pp 659 – 674 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] caractérisation [Termes IGN] données GPS [Termes IGN] erreur systématique [Termes IGN] filtre de Kalman [Termes IGN] filtre passe-bas [Termes IGN] GPS en mode cinématique [Termes IGN] impact sur les données [Termes IGN] phase GPS [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur bifréquence Résumé : (Auteur) The integer ambiguity resolution enabled precise point positioning (PPP-RTK) has been proven advantageous in a wide range of applications. The realization of PPP-RTK concerns the isolation of satellite phase biases (SPBs) and other corrections from a network of Global Positioning System (GPS) reference receivers. This is generally based on Kalman filter in order to achieve real-time capability, in which proper modeling of the dynamics of various types of unknowns remains crucial. This paper seeks to gain insight into how to reasonably deal with the dynamic behavior of the estimable receiver phase biases (RPBs). Using dual-frequency GPS data collected at six colocated receivers over days 50–120 of 2015, we analyze the 30-s epoch-by-epoch estimates of L1 and wide-lane (WL) RPBs for each receiver pair. The dynamics observed in these estimates are a combined effect of three factors, namely the random measurement noise, the multipath and the ambient temperature. The first factor can be overcome by turning to a real-time filter and the second by considering the use of a sidereal filtering. The third factor has an effect only on the WL, and this effect appears to be linear. After accounting for these three factors, the low-pass-filtered, sidereal-filtered, epoch-by-epoch estimates of L1 RPBs follow a random walk process, whereas those of WL RPBs are constant over time. Properly modeling the dynamics of RPBs is vital, as it ensures the best convergence of the Kalman-filtered, between-satellite single-differenced SPB estimates to their correct values and, in turn, shortens the time-to-first-fix at user side. Numéro de notice : A2018-151 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1085-z Date de publication en ligne : 13/11/2017 En ligne : https://doi.org/10.1007/s00190-017-1085-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89764 [article]

Group delay variations of GPS transmitting and receiving antennas / Lambert Wanninger in Journal of geodesy, vol 91 n° 9 (September 2017)  

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High-latitude ionospheric irregularity drift velocity estimation using spaced GPS receiver carrier phase time–frequency analysis / Jun Wang in IEEE Transactions on geoscience and remote sensing, vol 53 n° 11 (November 2015)  

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Particle filter-based estimation of inter-frequency phase bias for real-time GLONASS integer ambiguity resolution / Yumiao Tian in Journal of geodesy, vol 89 n° 11 (november 2015)  

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Carrier-phase ambiguity resolution: Handling the biases for improved triple-frequency PPP convergence / Denis Laurichesse in GPS world, vol 26 n° 4 (April 2015)  

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A Realistic and Easy-to-Implement Weighting Model for GPS Phase Observations / Xiaoguang Luo in IEEE Transactions on geoscience and remote sensing, vol 52 n° 10 tome 1 (October 2014)  

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Empirical modelling of site-specific errors in continuous GPS data / Michael Moore in Journal of geodesy, vol 88 n° 9 (September 2014)  

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Cycle slips: Detection and correction using inertial aiding / Malek O. Karaim in GPS world, vol 25 n° 1 (January 2014)

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Recent developments in Precise Point Positioning / Sunil Bisnath in Geomatica, vol 66 n° 2 (June 2012)  

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GPS snow depth meter with geometry-free linear combinations of carrier phases / M. Ozeki in Journal of geodesy, vol 86 n° 3 (March 2012)  

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Multipath minimization method: mitigation through adaptive filtering for machine automation applications / L. Serrano in GPS world, vol 22 n° 7 (July 2011)

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