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Alerte-GNSS & météo
- A new method for improving the performance of an ionospheric model developed by multi-instrument measurements based on artificial neural network [Article/Communication] / Wang Li, Auteur ; Changyong He, Auteur ; Andong Hu, Auteur ; Dongsheng Zhao, Auteur ; Yi Shen, Auteur ; Kefei Zhang, Auteur . - 2021 . - pp 20 - 34.bibliographieLangues : Anglais (eng)in Advances in space research > vol 67 n° 1 (January 2021) . - pp 20 - 34
Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] correction ionosphérique[Termes IGN] image Formosat/COSMIC[Termes IGN] modèle ionosphérique[Termes IGN] réseau neuronal artificiel[Termes IGN] teneur totale en électrons Résumé : (auteur) There are remarkable ionospheric discrepancies between space-borne (COSMIC) measurements and ground-based (ionosonde) observations, the discrepancies could decrease the accuracies of the ionospheric model developed by multi-source data seriously. To reduce the discrepancies between two observational systems, the peak frequency (foF2) and peak height (hmF2) derived from the COSMIC and ionosonde data are used to develop the ionospheric models by an artificial neural network (ANN) method, respectively. The averaged root-mean-square errors (RMSEs) of COSPF (COSMIC peak frequency model), COSPH (COSMIC peak height model), IONOPF (Ionosonde peak frequency model) and IONOPH (Ionosonde peak height model) are 0.58 MHz, 19.59 km, 0.92 MHz and 23.40 km, respectively. The results indicate that the discrepancies between these models are dependent on universal time, geographic latitude and seasons. The peak frequencies measured by COSMIC are generally larger than ionosonde’s observations in the nighttime or middle-latitudes with the amplitude of lower than 25%, while the averaged peak height derived from COSMIC is smaller than ionosonde’s data in the polar regions. The differences between ANN-based maps and references show that the discrepancies between two ionospheric detecting techniques are proportional to the intensity of solar radiation. Besides, a new method based on the ANN technique is proposed to reduce the discrepancies for improving ionospheric models developed by multiple measurements, the results indicate that the RMSEs of ANN models optimized by the method are 14–25% lower than the models without the application of the method. Furthermore, the ionospheric model built by the multiple measurements with the application of the method is more powerful in capturing the ionospheric dynamic physics features, such as equatorial ionization, Weddell Sea, mid-latitude summer nighttime and winter anomalies. In conclusion, the new method is significant in improving the accuracy and physical characteristics of an ionospheric model based on multi-source observations. Numéro de notice : A2021-986 Affiliation des auteurs : ENSG+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2020.07.032 Date de publication en ligne : 16/12/2020 En ligne : https://doi.org/10.1016/j.asr.2020.07.032 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102912 Predicting AIS reception using tropospheric propagation forecast and machine learning (2022)
Predicting AIS reception using tropospheric propagation forecast and machine learning [Article/Communication] / Zackary Vanche, Auteur ; Ambroise Renaud, Auteur ; Aldo Napoli, Auteur . - New York : Institute of Electrical and Electronics Engineers IEEE, 2022.bibliographieLangues : Anglais (eng)Descripteur : [Termes IGN] apprentissage automatique[Termes IGN] carte thématique[Termes IGN] identification automatique[Termes IGN] navigation maritime[Termes IGN] navire[Termes IGN] récepteur[Termes IGN] troposphère Résumé : (auteur) The aim of this paper is to present a methodology for modelling and predicting the coverage of an Automatic Identification System (AIS) station based on tropospheric index forecast maps and modelling methods from machine learning. The aim of this work is to cartographically represent the areas in which the AIS signals emitted by ships will be received by a coastal station. This work contributes to the improvement of maritime situational awareness and to the detection of anomalies at sea [1], and in particular to the identification of AIS message falsifications [2] (ubiquity of a vessel by identity theft, falsification of GPS positions and deactivation of AIS). Numéro de notice : C2022-036 Affiliation des auteurs : ENSG+Ext (2020- ) Autre URL associée : vers HAL Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.23919/USNC-URSI52669.2022.9887465 En ligne : https://doi.org/10.23919/USNC-URSI52669.2022.9887465 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101606 On enhanced PPP with single difference between-satellite ionospheric constraints
On enhanced PPP with single difference between-satellite ionospheric constraints [Article/Communication] / Yan Xiang, Auteur ; Xin Chen, Auteur ; Ling Pei, Auteur ; et al., Auteur . - 2022 . - n° 505.bibliographieLangues : Anglais (eng)in Navigation : journal of the Institute of navigation > vol 69 n° 1 (Spring 2022) . - n° 505Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] correction ionosphérique[Termes IGN] modèle stochastique[Termes IGN] positionnement ponctuel précis[Termes IGN] retard ionosphèrique[Termes IGN] simple différence[Termes IGN] temps de convergence Résumé : (auteur) Applications of precise point positioning (PPP) are limited by PPP’s long convergence time. One effective way to shorten the convergence time is to apply ionospheric constraints because of the external ionospheric information. The conventional way to do this is to apply high precision but biased ionospheric corrections. The limitations of the method are that all ionospheric constraints must be derived from the same set of reference stations to have the same data. An approach based on single differences between satellite ionospheric constraints (SDBS-IONO) is developed to address the data issue due to having no common satellite visibility. The proposed method is more flexible and scalable in terms of adding ionospheric constraints. Based on a network of about 130 stations, we validated the proposed SDBS-ION method and compared it to the conventional method. Our results confirm that the ionospheric constraints enhance the PPP convergence time significantly depending on the accuracy of ionospheric constraints. Finally, we discuss crucial factors regarding how long and accurate the effectiveness of ionospheric constraints are in reducing PPP convergence time. Numéro de notice : A2022-820 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.505 Date de publication en ligne : 07/11/2021 En ligne : https://doi.org/10.33012/navi.505 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101988 Estimation of swell height using spaceborne GNSS-R data from eight CYGNSS satellites
Estimation of swell height using spaceborne GNSS-R data from eight CYGNSS satellites [Article/Communication] / Yanli Zheng, Auteur ; Fu Zheng, Auteur ; Cheng Yang, Auteur ; et al., Auteur . - 2022 . - n° 4640.bibliographieLangues : Anglais (eng)in Remote sensing > vol 14 n° 18 (September-2 2022) . - n° 4640Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] données GLONASS[Termes IGN] données GPS[Termes IGN] double différence[Termes IGN] latitude[Termes IGN] positionnement ponctuel précis[Termes IGN] positionnement statique[Termes IGN] retard troposphérique zénithal[Termes IGN] temps de convergence Résumé : (auteur) The orbital inclination angle of the GLONASS constellation is about 10° larger than that of GPS, Galileo, and BDS. Theoretically, the higher orbital inclination angle could provide better observation geometry in high latitude regions. A wealth of research has investigated the positioning accuracy of GLONASS and its impact on multi-GNSS, but rarely considered the contribution of the GLONASS constellation’s large orbit inclination angle. The performance of GLONASS in different latitude regions is evaluated in both stand-alone mode and integration with GPS in this paper. The performance of GPS is also presented for comparison. Three international GNSS service (IGS) networks located in high, middle, and low latitudes are selected for the current study. Multi-GNSS data between January 2021 and June 2021 are used for the assessment. The data quality check shows that the GLONASS data integrity is significantly lower than that of GPS. The constellation visibility analysis indicates that GLONASS has a much better elevation distribution than GPS in high latitude regions. Both daily double-difference network solutions and daily static Precise Point Positioning (PPP) solutions are evaluated. The statistical analysis of coordinate estimates indicates that, in high latitude regions, GLONASS has a comparable or even better accuracy than that of GPS, and GPS+GLONASS presents the best estimate accuracy; in middle latitude regions, GPS stand-alone constellation provides the best positioning accuracy; in low latitude regions, GLONASS offers the worst accuracy, but the positioning accuracy of GPS+GLONASS is better than that of GPS. The tropospheric estimates of GLONASS do not present a resemblance regional advantage as coordinate estimates, which is worse than that of GPS in all three networks. The PPP processing with combined GPS and GLONASS observations reduces the convergence time and improves the accuracy of tropospheric estimates in all three networks. Numéro de notice : A2022-770 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3390/rs14184640 Date de publication en ligne : 16/09/2022 En ligne : https://doi.org/10.3390/rs14184640 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101796 Estimation of ionospheric total electron content using GNSS observations derived from a smartphone
Estimation of ionospheric total electron content using GNSS observations derived from a smartphone [Article/Communication] / Li Xu, Auteur ; Jiuping Zha, Auteur ; Min Li, Auteur ; et al., Auteur . - 2022 . - n° 138.bibliographieLangues : Anglais (eng)in GPS solutions > vol 26 n° 4 (October 2022) . - n° 138Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale[Termes IGN] modèle ionosphérique[Termes IGN] phase[Termes IGN] pondération[Termes IGN] série de Fourier[Termes IGN] téléphone intelligent[Termes IGN] teneur totale en électrons[Termes IGN] teneur verticale totale en électrons Résumé : (auteur) The global navigation satellite system (GNSS) measurements to determine ionospheric total electron content (TEC) are mainly derived from expensive geodetic-grade receivers, which are not conducive to high-density placement. In this work, we present an analysis of the performance of ionospheric TEC determined by GNSS dual-frequency measurements derived from the smartphone, taking the Xiaomi 8 (XMI8) as an example. First, the ionospheric observable is retrieved from the code and carrier phase data using the carrier-to-code leveling technique and a new carrier-to-noise weighting strategy instead of an elevation weighting strategy, considering the characteristic of the GNSS measurements from smartphones. Then, the absolute ionospheric slant TEC (STEC) values are isolated from the ionospheric observables by modeling with the generalized trigonometric series function. The experimental data, covering over 120 h, were taken from two situations: one is the data collected by the original smartphone antenna; the other is the external geodetic-grade antenna. The TEC data obtained from the collocated geodetic-grade receiver are used as reference data to evaluate the performance of the TEC values from XMI8. Compared to the reference data, the evaluation results show that the ionospheric STEC extraction accuracy can reach total electron content unit (TECU) values of 0.17 and 0.11 under the two different situations in the continuous carrier phase satellite arc without cycle slips. In addition, the VTEC modeling accuracy is above 5 and 2 TECU in the two different situations, respectively. Thus, we concluded that consumer-level GNSS chipsets are highly potential in the future to increase the ionospheric monitoring station density due to their low costs and good data quality. Numéro de notice : A2022-713 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-022-01329-w Date de publication en ligne : 04/09/2022 En ligne : https://doi.org/10.1007/s10291-022-01329-w Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101591 An efficient method to compensate receiver clock jumps in real-time precise point positioning
An efficient method to compensate receiver clock jumps in real-time precise point positioning [Article/Communication] / Shaoguang Xu, Auteur ; Jialu Long, Auteur ; Jinling Wang, Auteur ; et al., Auteur . - 2022 . - n° 5222.bibliographieLangues : Anglais (eng)in Remote sensing > vol 14 n° 20 (October-2 2022) . - n° 5222Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] ambiguïté entière[Termes IGN] décalage d'horloge[Termes IGN] erreur de positionnement[Termes IGN] glissement de cycle[Termes IGN] horloge du récepteur[Termes IGN] phase[Termes IGN] positionnement cinématique en temps réel[Termes IGN] positionnement par GNSS[Termes IGN] positionnement ponctuel précis[Termes IGN] retard troposphérique zénithal[Termes IGN] temps réel Résumé : (auteur) In global navigation satellite systems (GNSSs)-based positioning, user receiver clock jump is a common phenomenon on the low-cost receiver clocks and can break the continuity of observation time tag, carrier phase and pseudo range. The discontinuity may affect precise point positioning-related parameter estimation, including receiver clock error, position, troposphere and ionosphere parameters. It is important to note that these parameters can be used for timing, positioning, atmospheric inversion and so on. In response to this problem, the receiver clock jumps are divided into two types. The first one can be expressed by the carrier phase and pseudo range having the same scale jump, and the second one is that they are having different scale jumps. For the first type, if a small priori variance of receiver clock error is provided, it can affect the accuracy of ionospheric delay estimation both in static and kinematic mode, while in the latter mode, it also affects position estimation. However, if large process noise is provided, numerical problems may arise since other parameters’ process noises are usually small, it is proposed to use the single point positioning with pseudo ranges to provide a priori value of receiver clock error, and an empiric value is assigned to its prior variance, this handle can avoid the above problems. For the second type, instead of compensating so many raw observations in the traditional methods, it is proposed to compensate the ambiguities at the clock jump epochs only in a new method. The new method corrects the Melbourne–Wubbena (MW) combination firstly in order to avoid the misjudging of cycle slips for current epoch, and the second step is to compensate the corresponding ambiguities, then, after Kalman filtering, the MW and its mean should be corrected back in order to avoid the misjudging of cycle slips at the next epoch. This approach has the advantage of handling the clock jump epoch-wise and can avoid correcting the rest of the observations as the traditional methods used to. With the numerical validation examples both in static and kinematic modes, it shows the new method is simple but efficient for real time precise point positioning (PPP). Numéro de notice : A2022-792 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3390/rs14205222 Date de publication en ligne : 19/10/2022 En ligne : https://doi.org/10.3390/rs14205222 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101909 - On the relation of GNSS phase center offsets and the terrestrial reference frame scale: a semi-analytical analysis [Article/Communication] / Oliver Montenbruck, Auteur ; Peter Steigenberger, Auteur ; Arturo Villiger, Auteur ; Paul Rebischung, Auteur . - 2022 . - n° 90.bibliographieLangues : Anglais (eng)in Journal of geodesy > vol 96 n° 11 (November 2022) . - n° 90
Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] antenne GNSS[Termes IGN] centre de phase[Termes IGN] décalage d'horloge[Termes IGN] hauteur (coordonnée)[Termes IGN] International Terrestrial Reference Frame[Termes IGN] orbitographie[Termes IGN] phase[Termes IGN] positionnement par GNSS[Termes IGN] retard troposphérique zénithal[Termes IGN] station GNSS Résumé : (auteur) Phase center offsets (PCOs) of global navigation satellites systems (GNSS) transmit antennas along the boresight axis introduce line-of-sight-dependent range changes in the modeling of GNSS observations that are strongly correlated with the estimated station heights. As a consequence, changes in the adopted PCOs impact the scale of GNSS-based realizations of the terrestrial reference frame (TRF). Vice versa, changes in the adopted TRF scale require corrections to the GNSS transmit antenna PCOs for consistent observation modeling. Early studies have determined an approximate value of α=−0.050 for the ratio of station height changes and satellite PCO changes in GPS orbit determination and phase center adjustment. However, this is mainly an empirical value and limited information is available on the actual PCO-scale relation and how it is influenced by other factors. In view of the recurring need to adjust the IGS antenna models to new ITRF scales, a semi-analytical model is developed to determine values of α for the four current GNSSs from first principles without a need for actual network data processing. Given the close coupling of satellite boresight angle and station zenith angle, satellite PCO changes are essentially compensated by a combination of station height, zenith troposphere delay, and receiver clock offset. As such, the value of α depends not only on the orbital altitude of the considered GNSS but also on the elevation-dependent distribution of GNSS observations and their weighting, as well as the elevation mask angle and the tropospheric mapping function. Based on the model, representative values of αGPS=−0.051, αGLO=−0.055, αGAL=−0.041, and αBDS-3=−0.046 are derived for GPS, GLONASS, Galileo, and BeiDou-3 at a 10∘ elevation cutoff angle. These values may vary by Δα≈0.003 depending on the specific model assumptions and data processing parameters in a precise orbit determination or precise point positioning. Likewise changes of about ±0.003 can be observed when varying the cutoff angle between 5∘ and 15∘. Numéro de notice : A2022-836 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01678-x Date de publication en ligne : 09/11/2022 En ligne : https://doi.org/10.1007/s00190-022-01678-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102033 Testing of new ionospheric models along the meridian 110° E over the Northern Hemisphere
Testing of new ionospheric models along the meridian 110° E over the Northern Hemisphere [Article/Communication] / Olga Maltseva, Auteur ; Artem Kharakhashyan, Auteur ; Tatyana Nikitenko, Auteur . - 2022 . - pp 544 - 553.bibliographieLangues : Anglais (eng)in Geodesy and Geodynamics > vol 13 n° 6 (November 2022) . - pp 544 - 553Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] hémisphère Nord[Termes IGN] méridien[Termes IGN] modèle ionosphérique[Termes IGN] teneur totale en électrons Résumé : (auteur) Despite the continuous improvement of the widely used empirical model international reference ionosphere (IRI), the recently appeared new models must be tested worldwide. Testing along the meridians has the advantage of dealing with the latitudinal dependent parameters. This paper uses new models of parameters foF2 (critical frequency), TEC (total electron content), and τ (equivalent slab thickness of the ionosphere), which are of great importance for evaluating the effects of space weather. IRI-Plas, NNT2F2, and NTSM models were tested using data from 6 ionosondes located along the meridian 110° E in March 2012. It is shown that the IRI-Plas model provides the closest values to experiment with respect to τ, while the NTSM model provides a rather limited reflection of the latitude dependence. Analyses of foF2(NNT2F2) have shown that, the NNT2F2 model provides good conformity with experimental values in this area, but it is very dependent on the TEC processing method. The latitudinal dependences of foF2 obtained with TEC and polynomial dependence τ(Appr) showed the presence of positive deviations from medians not only during disturbances but also quiet periods, longitudinally at the meridian. Numéro de notice : A2022-763 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1016/j.geog.2022.06.002 Date de publication en ligne : 02/07/2022 En ligne : https://doi.org/10.1016/j.geog.2022.06.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101783 - Identifying spurious cycle slips based on iterative filtering under disturbed ionospheric conditions for undifferenced GNSS observations [Article/Communication] / Yan Xiang, Auteur ; Sijie Lyu, Auteur ; Wenxian Yu, Auteur . - 2022 . - pp 3582 - 3593.bibliographieLangues : Anglais (eng)in Advances in space research > vol 70 n° 11 (December 2022) . - pp 3582 - 3593
Descripteur : [Termes IGN] erreur de positionnement[Termes IGN] filtre[Termes IGN] glissement de cycle[Termes IGN] itération[Termes IGN] perturbation ionosphérique[Termes IGN] phase GNSS[Termes IGN] positionnement ponctuel précis[Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) The TurboEdit method is widely used to detect cycle slips on the global navigation satellite system (GNSS) carrier-phase measurements. However, it leads to an increasing number of false alarms in detecting cycle slips under disturbed ionospheric conditions. Besides, once the method detects a cycle slip at one satellite, it treats dual frequencies with cycle slips rather than at one frequency. Considering these two challenges, we developed a solution-based iterative filter detection method to reduce the number of spurious cycle slip detection under disturbed ionospheric conditions. The method initially assumes that there is no cycle slip at each frequency. We then estimate the solutions without cycle slips. A decision of exiting cycle slips is made by examining and comparing the two results solutions with or without cycle slips in terms of usable satellites, ambiguities, and residuals. The uncombined precise point positioning (PPP) during disturbed ionospheric conditions on 17 March 2015 at high latitude was studied to validate the proposed method. Results showed that the detected number of spurious cycle slips was reduced significantly. With fewer marked cycle slips, more stable and smoother positioning performance was achieved when fewer ambiguity parameters were reinitialized. Numéro de notice : A2022-861 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1016/j.asr.2022.08.008 Date de publication en ligne : 08/08/2022 En ligne : https://doi.org/10.1016/j.asr.2022.08.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102144 Multi-frequency simulation of ionospheric scintillation using a phase-screen model
Multi-frequency simulation of ionospheric scintillation using a phase-screen model [Article/Communication] / Fernando D. Nunes, Auteur ; Fernando M.G. Sousa, Auteur ; José M.V. Marçal, Auteur . - 2022 . - n° 545.bibliographieLangues : Anglais (eng)in Navigation : journal of the Institute of navigation > vol 69 n° 4 (Fall 2022) . - n° 545Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] amplitude[Termes IGN] correction ionosphérique[Termes IGN] fréquence multiple[Termes IGN] ionosphère[Termes IGN] méthode de Monte-Carlo[Termes IGN] phase[Termes IGN] scintillation[Termes IGN] série temporelle[Termes IGN] signal GNSS[Termes IGN] teneur totale en électrons Résumé : (auteur) A fast Monte Carlo technique to simulate equatorial ionospheric scintillation on global navigation satellite system signals is proposed. The algorithm uses a single-layer phase-screen model of the ionosphere and the scintillation is expressed as a Huygens-Fresnel integral (HFI). By assuming a specially-tailored random phase screen, the HFI can be expressed in closed form as a combination of Fresnel integrals. We statistically characterize the amplitude and phase computed by the HFI for different values of the scintillation index S4. Results for the L1, L2, and L5 bands were obtained and compared with real data, showing good agreement. Some of the advantages of the proposed technique are: (a) the amplitude and phase of the scintillation process are simultaneously obtained; (b) arbitrarily long ionospheric scintillation time series with pre-defined stationary characteristics are synthesized; and (c) several scintillation time series corresponding to different carrier frequencies are generated using a common phase-screen model. Numéro de notice : A2022-918 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.545 Date de publication en ligne : 18/06/2022 En ligne : https://doi.org/10.33012/navi.545 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102446 Navigation and Ionosphere Characterization Using High-Frequency Signals: A Performance Analysis
Navigation and Ionosphere Characterization Using High-Frequency Signals: A Performance Analysis [Article/Communication] / Yoav Baumgarten, Auteur ; M.L. Psiaki, Auteur ; David L. Hysell, Auteur . - 2022 . - n° 546.bibliographieLangues : Anglais (eng)in Navigation : journal of the Institute of navigation > vol 69 n° 4 (Fall 2022) . - n° 546Descripteur : [Vedettes matières IGN] Traitement du signal[Termes IGN] algorithme de Gauss-Newton[Termes IGN] correction du signal[Termes IGN] correction ionosphérique[Termes IGN] matrice de covariance[Termes IGN] mesurage de phase[Termes IGN] modèle ionosphérique[Termes IGN] propagation du signal[Termes IGN] récepteur[Termes IGN] teneur verticale totale en électrons Résumé : (auteur) The performance of a proposed high-frequency (HF) navigation concept is analyzed using simulated data. The method relies on pseudorange and beat carrier-phase measurements of signals that propagate in the ionosphere along curved trajectories, where signals are refracted back downwards from the ionosphere. It has been demonstrated that the location of a receiver can be determined if several signals, broadcast from beacons at different locations, are received and processed at a user receiver. A challenge of determining exact signal paths is the uncertainty in the ionosphere’s electron density distribution. This is addressed by a batch filter that simultaneously estimates the receiver position along with corrections to a parametric model of the ionosphere. A previous paper developed the theory and batch filter for this concept. The present study examines its potential performance. Total horizontal position errors on the order of tens to hundreds of meters are achieved, depending on the case’s characteristics. Numéro de notice : A2022-919 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.546 Date de publication en ligne : 19/06/2022 En ligne : https://doi.org/10.33012/navi.546 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102448 - Spatiotemporal accuracy evaluation and errors analysis of global VTEC maps using a simulation technique [Article/Communication] / Jian Lin, Auteur ; Xinxing Li, Auteur ; Shenfeng Gu, Auteur ; et al., Auteur . - 2023 . - n° 6.bibliographieLangues : Anglais (eng)in GPS solutions > vol 27 n° 1 (January 2023) . - n° 6
Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] données GPS[Termes IGN] harmonique sphérique[Termes IGN] modèle cartographique[Termes IGN] modèle ionosphérique[Termes IGN] phase[Termes IGN] rayonnement solaire[Termes IGN] simulation[Termes IGN] station GPS[Termes IGN] teneur verticale totale en électrons Résumé : (auteur) The computation of vertical total electron content (VTEC) maps has become an important issue gradually for the international GNSS service. Given the current literature reports, little research is involved in the quantitative analysis of each error of the VTEC map and the spatiotemporal characteristic of global VTEC accuracy. Based on the single layer model and sphere harmonic function, we propose an approach using simulated GPS data to comprehensively verify the accuracy of the VTEC map. The spatiotemporal characteristic of global VTEC accuracy and the errors induced by different processing steps, i.e., carrier phase to code leveling, mapping function (MF), DCB estimation and coefficient fitting, are analyzed and discussed in detail. In addition, the effect of solar activity on the accuracy of the global VTEC map, MF and DCB estimation has been discussed. The results suggest: First, it is found that the MF error at sunrise is more significant than that at sunset, and this important characteristic can be proven based on the analysis of theory and ionospheric radio occultation and VTEC measurements; second, the MF is the most significant error source in the VTEC processing for regions with dense and homogeneous distributed GPS stations, e.g., North America and Europe. The VTEC accuracy in these regions can be improved by 100% with the satellite elevation cutoff angle increasing from 12° to 30°; finally, compared with the global VTEC accuracy using 350 GPS stations observations, the accuracy is improved by 306% based on the double GPS stations with even distribution. Numéro de notice : A2023-002 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01343-y Date de publication en ligne : 13/10/2022 En ligne : https://doi.org/10.1007/s10291-022-01343-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101871 - Establishing a high-precision real-time ZTD model of China with GPS and ERA5 historical data and its application in PPP [Article/Communication] / Pengfei Xia, Auteur ; Mengxiang Tong, Auteur ; Shirong Ye, Auteur ; et al., Auteur . - 2023 . - n° 2.bibliographieLangues : Anglais (eng)in GPS solutions > vol 27 n° 1 (January 2023) . - n° 2
Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] Chine[Termes IGN] correction troposphérique[Termes IGN] données météorologiques[Termes IGN] grille[Termes IGN] positionnement ponctuel précis[Termes IGN] retard troposphérique zénithal[Termes IGN] série de Fourier[Termes IGN] série temporelle[Termes IGN] station GNSS[Termes IGN] temps de convergence[Termes IGN] temps réel[Termes IGN] variation diurne Résumé : (auteur) A high-precision real-time troposphere model is constructed by combining ground-based GNSS observation data and the latest European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5). First, the zenith tropospheric delay (ZTD) is extracted in real time with high accuracy by combining the data of more than 500 GNSS stations in the Crustal Movement Observation Network of China (CMONOC) and national reference station network (NRSN); second, a grid model of the elevation normalization model (ENM) in China using ERA5 data is constructed, which takes into account the annual, semiannual and daily cycles. The ZTD estimated by GNSS stations at different heights based on precise point positioning (PPP) is normalized to a uniform height based on ENM; in addition, the optimal smoothing factors of the Gauss distance weighting function in different seasons are determined based on ERA5, which contributes to improved accuracy of ZTD interpolated from GNSS-derived ZTD to ZTD at grid points; finally, a real-time 1° × 1°ZTD grid model of China is created; the broadcast interval is extended to 6 min from few seconds. The new ZTD model has been evaluated using the data of 15 GNSS stations in China in 2020. The test results show that the new ZTD model deviates from the reference value with a mean value better than − 0.09 cm and RMSE, better than 1.44 cm compared with the ZTD estimated by post-processing GNSS, while the mean value of the deviation is -0.13 cm, and the RMSE is approximately 3.11 cm compared with radiosonde-derived ZTD. The new ZTD grid model can be used to enhance GNSS/PPP. Two weeks of GNSS observations, one week in winter and another in summer, were randomly collected for PPP processing. The statistical results show the convergence time in the vertical directions is shortened by 37.4% and 38.6% at the 95% and 68% confidence levels after ZTD constraints are applied to the float PPP solution, respectively. Numéro de notice : A2023-004 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01338-9 Date de publication en ligne : 07/10/2022 En ligne : https://doi.org/10.1007/s10291-022-01338-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101874 - Parameterisation of the GNSS troposphere tomography domain with optimisation of the nodes’ distribution [Article/Communication] / Estera Trzcina, Auteur ; Witold Rohm, Auteur ; Kamil Smolak, Auteur . - 2023 . - n° 2.bibliographieLangues : Anglais (eng)in Journal of geodesy > vol 97 n° 1 (January 2023) . - n° 2
Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale[Termes IGN] données GNSS[Termes IGN] interpolation bilinéaire[Termes IGN] modèle météorologique[Termes IGN] optimisation (mathématiques)[Termes IGN] radiosondage[Termes IGN] récepteur GNSS[Termes IGN] retard troposphérique[Termes IGN] retard troposphérique zénithal[Termes IGN] système de grille globale discrète[Termes IGN] teneur en vapeur d'eau[Termes IGN] tomographie[Termes IGN] troposphère Résumé : (auteur) Water vapour is a highly variable constituent of the troposphere; thus, its high-resolution measurements are of great importance to weather prediction systems. The Global Navigation Satellite Systems (GNSS) are operationally used in the estimation of the tropospheric state and assimilation of the results into the weather models. One of the GNSS techniques of troposphere sensing is tomography which provides 3-D fields of wet refractivity. The tomographic results have been successfully assimilated into the numerical weather models, showing the great potential of this technique. The GNSS tomography can be based on two different approaches to the parameterisation of the model’s domain, i.e. block (voxel-based) or grid (node-based) approach. Regardless of the parameterisation approach, the tomographic domain should be discretised, which is usually performed in a regular manner, with a grid resolution depending on the mean distance between the GNSS receivers. In this work, we propose a new parameterisation approach based on the optimisation of the tomographic nodes’ location, taking into account the non-uniform distribution of the GNSS information in the troposphere. The experiment was performed using a dense network of 16 low-cost multi-GNSS receivers located in Wrocław and its suburbs, with a mean distance of 3 km. Cross-validation of four different parameterisation approaches is presented. The validation is performed based on the Weather Research and Forecasting model as well as radiosonde observations. The new approach improves the results of wet refractivity estimation by 0.5–2 ppm in terms of RMSE, especially for altitudes of 0.5–2.0 km. Numéro de notice : A2023-044 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : https://doi.org/10.1007/s00190-022-01691-0 Date de publication en ligne : 30/12/2022 En ligne : https://doi.org/10.1007/s00190-022-01691-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102343 Undifferenced and uncombined GNSS time and frequency transfer with integer ambiguity resolution
Undifferenced and uncombined GNSS time and frequency transfer with integer ambiguity resolution [Article/Communication] / Xiaolong Mi, Auteur ; Baocheng Zhang, Auteur ; Ahmed El-Mowafy, Auteur ; et al., Auteur . - 2023 . - n° 13.bibliographieLangues : Anglais (eng)in Journal of geodesy > vol 97 n° 2 (February 2023) . - n° 13Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] ambiguïté entière[Termes IGN] modèle ionosphérique[Termes IGN] positionnement cinématique en temps réel[Termes IGN] positionnement ponctuel précis[Termes IGN] résolution d'ambiguïté[Termes IGN] retard ionosphèrique[Termes IGN] temps-fréquence Résumé : (auteur) Precise point positioning (PPP) has been a competitive global navigation satellite system (GNSS) technique for time and frequency transfer. However, the classical PPP is usually based on the ionosphere-free combination of dual-frequency observations, which has limited flexibility in the multi-frequency scenario. More importantly, the unknown integer ambiguities are not restored to the integer nature, making the advantage of high-precision carrier phase observations underutilized. In this contribution, using the undifferenced and uncombined (UDUC) observations, we derive the time and frequency transfer model suitable for multi-constellation and multi-frequency scenarios. Notably, in short- and medium-baseline time and frequency transfer, the ionosphere-fixed and ionosphere-weighted UDUC models are derived, respectively, by making full use of the single-differenced (SD) ionospheric constraints. The proposed model can be applied to short-, medium- and long-baseline time and frequency transfer. The ambiguities are solved in a double-differenced (DD) form and can thus be restored to integers. To verify the feasibility of the model, GPS data from several time laboratories were collected, and the performance of the time and frequency transfer were analyzed with different baseline lengths. The results showed that the ionosphere-fixed and ionosphere-weighted UDUC models with integer ambiguity resolution could improve the frequency stability by 25–60% and 9–30% at an averaging time of several tens of seconds to 1 day for short- and medium-baseline, respectively. Concerning the long-baseline, the UDUC model is 10–25% more stable than PPP for averaging time below a few thousands second and over 1 day. Numéro de notice : A2022-613 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01689-8 Date de publication en ligne : 06/02/2023 En ligne : https://doi.org/10.1007/s00190-022-01689-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102677 - Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations [Article/Communication] / Xulei Jin, Auteur ; Shuli Song, Auteur . - 2023 . - n° 27.bibliographieLangues : Anglais (eng)in Journal of geodesy > vol 97 n° 3 (March 2023) . - n° 27
Descripteur : [Termes IGN] carte ionosphérique mondiale[Termes IGN] données Jason[Termes IGN] modèle ionosphérique[Termes IGN] temps réel[Termes IGN] teneur totale en électrons[Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) For the purposes of routinely providing reliable and low-latency Global Ionosphere Maps (GIMs), a method of estimating hourly updated near real-time GIM with a time latency of about 1–2 h based on a 24-h data sliding window of Global Navigation Satellite System (GNSS) near real-time observations and real-time data streams was presented. On the basis of the implementation of near real-time GIM estimation, an hourly updated GIM nowcasting method was further proposed to improve the accurate of short-term total electron content (TEC) prediction. We estimated the Shanghai Astronomical Observatory near real-time GIM (SHUG) and nowcasting GIM (SHPG) in the solar relatively active year (2014) and quiet year (2021), and employed GIMs provided by the International GNSS Service, the Global Positioning System (GPS) differential slant TECs (dSTECs) extracted from global independent GNSS stations, and the vertical TECs (VTECs) inverted from satellite altimetry as the references to validate the estimated results. The GPS dSTECs evaluation results show that SHUG behaves fairly consistent with the rapid GIMs, with a discrepancy of less than 1 TEC unit (TECu) overall. The standard deviations (STDs) of SHUG with respect to Jason-2/-3 VTECs are no more than 10% over the majority of rapid GIMs due to the instability of observations. The performance of 1-h nowcasting SHPG is significantlybetter than the Center for Orbit Determination in Europe (CODE) 1-day predicted GIM (C1PG). GPS dSTEC validation results indicate that 1-h nowcasting SHPG is 1 to 2 TECu more reliable than C1PG in eventful ionospheric electron activity regions, and it outperforms the C1PG by 10% overall versus Jason-2/-3 VTECs. The hourly updated SHUG and SHPG have relatively high reliability and low time latency, and thus can provide excellent service for (near) real-time users and offer more accurate TEC background information than daily predicted GIM for real-time GIM estimation. Numéro de notice : A2023-181 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01715-3 Date de publication en ligne : 20/03/2023 En ligne : https://doi.org/10.1007/s00190-023-01715-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102950 - A tropospheric delay model to integrate ERA5 and GNSS reference network for mountainous areas: application to precise point positioning [Article/Communication] / Cuixian Lu, Auteur ; Yaxin Zhong, Auteur ; Zhilu Wu, Auteur ; et al., Auteur . - 2023 . - n° 81.bibliographieLangues : Anglais (eng)in GPS solutions > vol 27 n° 2 (April 2023) . - n° 81
Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale[Termes IGN] Australie[Termes IGN] Continuously Operating Reference Station network [Termes IGN] convergence[Termes IGN] ERA5[Termes IGN] montagne[Termes IGN] positionnement ponctuel précis[Termes IGN] retard troposphérique[Termes IGN] retard troposphérique zénithal[Termes IGN] station GNSS[Termes IGN] teneur en vapeur d'eau Résumé : (auteur) In this study, a tropospheric delay model that integrates tropospheric delays derived from the European Centre for Medium-Range Weather Forecasts fifth-generation global atmospheric reanalysis and the Continuously Operating Reference Station (CORS) network observations in mountainous areas is established, which is then applied to improve GNSS precise point positioning (PPP). Observations of GNSS stations in the Great Dividing Range of eastern Australia are selected for the experiments. The performance of zenith wet delay (ZWD) retrieved from the integrated tropospheric model is evaluated with comparisons to precise point positioning (PPP) estimated ZWD values. Results show that the average root-mean-square value for ZWDs of the integrated tropospheric model is 8.03 mm for the eastern Australian CORS network, showing an improvement of 14.0% compared to that of the CORS interpolation model. Besides, the proposed tropospheric model is applied to regional augmentation precise positioning. Results present that the average positioning accuracy of the tropospheric model-corrected PPP solutions is 1.42 cm, 1.39 cm and 2.90 cm for the east, north and vertical components, respectively, revealing an improvement of 14.5%, 11.5% and 18.6% compared to the PPP solutions with regional CORS corrections. Meanwhile, almost all stations can achieve a faster solution convergence by performing the integrated tropospheric model-corrected PPP. All these results demonstrate the promising potential of the proposed tropospheric model in enhancing precise positioning as well as facilitating applications in the meteorological fields. Numéro de notice : A2023-183 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-023-01425-5 Date de publication en ligne : 03/03/2023 En ligne : https://doi.org/10.1007/s10291-023-01425-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102954 A consistent regional vertical ionospheric model and application in PPP-RTK under sparse networks
A consistent regional vertical ionospheric model and application in PPP-RTK under sparse networks [Article/Communication] / Sijie Lyu, Auteur ; Yan Xiang, Auteur ; Tiantian Tang, Auteur ; et al., Auteur . - 2023 . - n° 568.Langues : Anglais (eng)in Navigation : journal of the Institute of navigation > vol 70 n° 3 (Fall 2023) . - n° 568Descripteur : [Vedettes matières IGN] Géodésie spatiale[Termes IGN] carte ionosphérique mondiale[Termes IGN] correction ionosphérique[Termes IGN] modèle ionosphérique[Termes IGN] positionnement cinématique en temps réel[Termes IGN] positionnement ponctuel précis[Termes IGN] résolution d'ambiguïté[Termes IGN] retard ionosphèrique[Termes IGN] teneur totale en électrons[Termes IGN] teneur verticale totale en électrons Numéro de notice : A2023-201 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.568 Date de publication en ligne : 23/09/2022 En ligne : https://doi.org/10.33012/navi.568 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103096
