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An improved constrained simultaneous iterative reconstruction technique for ionospheric tomography / Yi Bin Yao in GPS solutions, Vol 24 n° 3 (July 2020)  

Public [article]  inGPS solutions > Vol 24 n° 3 (July 2020) Titre : An improved constrained simultaneous iterative reconstruction technique for ionospheric tomography Type de document : Article/Communication Auteurs : Yi Bin Yao, Auteur ; Changzhi Zhai, Auteur ; Jian Kong, Auteur ; et al., Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données GNSS [Termes IGN] interpolation [Termes IGN] modèle ionosphérique [Termes IGN] reconstruction 3D [Termes IGN] teneur totale en électrons [Termes IGN] tomographie [Termes IGN] voxel Résumé : (auteur) Global Navigation Satellite System (GNSS) is now widely used for continuous ionospheric observations. Three-dimensional computerized ionospheric tomography (3DCIT) is an important tool for the reconstruction of electron density distributions in the ionosphere through effective use of the GNSS data. More specifically, the 3DCIT technique is able to resolve the three-dimensional electron density distributions over the reconstructed area based on the GNSS slant total electron content (STEC) observations. We present an Improved Constrained Simultaneous Iterative Reconstruction Technique (ICSIRT) algorithm that differs from the traditional ionospheric tomography methods in 3 ways. First, the ICSIRT computes the electron density corrections based on the product of the intercept and electron density within voxels so that the assignment of corrections at different heights becomes more reasonable. Second, an Inverse Distance Weighted (IDW) interpolation is used to restrict the electron density values in the voxels not traversed by GNSS rays, thereby ensuring the smoothness of the reconstructed region. Also, to improve the reconstruction accuracy around the HmF2 (the peak height of the F2 layer) altitude, a multiresolution grid is adopted in the vertical direction, with a 10-km resolution from 200 to 420 km and a 50-km resolution at other altitudes. The new algorithm has been applied to the GNSS data over the European and North American regions in different case studies that involve different seasonal conditions as well as a major storm. In the European region experiment, reconstruction results show that the new ICSIRT algorithm can effectively improve the reconstruction of the GNSS data. The electron density profiles retrieved from ICSIRT are much closer to the ionosonde observations than those from its predecessor, namely, the Constrained Simultaneous Iteration Reconstruction Technique (CSIRT). The reconstruction accuracy is significantly improved. In the North American region experiment, the electron density profiles in ICSIRT results show better agreement with incoherent scatter radar observations than CSIRT, even for the topside profiles. Numéro de notice : A2020-227 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-00981-4 Date de publication en ligne : 18/04/2020 En ligne : https://doi.org/10.1007/s10291-020-00981-4 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94958 [article]

GLONASS inter-frequency phase bias rate estimation by single-epoch or Kalman filter algorithm / Yi Bin Yao in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1871 – 1882 Titre : GLONASS inter-frequency phase bias rate estimation by single-epoch or Kalman filter algorithm Type de document : Article/Communication Auteurs : Yi Bin Yao, Auteur ; Mingxian Hu, Auteur ; Xiayan Xu, Auteur ; Yadong He, Auteur Année de publication : 2017 Article en page(s) : pp 1871 – 1882 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] double différence [Termes IGN] erreur de phase [Termes IGN] filtre de Kalman [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GLONASS [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) GLONASS double-differenced (DD) ambiguity resolution is hindered by the inter-frequency bias (IFB) in GLONASS observation. We propose a new algorithm for IFB rate estimation to solve this problem. Although the wavelength of the widelane observation is several times that of the L1 observation, their IFB errors are similar in units of meters. Based on this property, the new algorithm can restrict the IFB effect on widelane observation within 0.5 cycles, which means the GLONASS widelane DD ambiguity can be accurately fixed. With the widelane integer ambiguity and phase observation, the IFB rate can be estimated using single-epoch measurements, called the single-epoch IFB rate estimation algorithm, or using the Kalman filter to process all data, called the Kalman filter-based IFB rate estimation algorithm. Due to insufficient accuracy of the IFB rate estimated from widelane observations, the IFB rate has to be further refined with L1 and L2 observations. A new reference satellite selection method is proposed to serve the IFB rate estimation. The experiment results show that the IFB rates on L1 and L2 bands are different, that an accurate IFB rate will help us to obtain more fixed solutions at places with serious occlusion, that the single-epoch IFB rate estimation algorithm can meet the requirements for real-time kinematic positioning with only 8% extra computational time, and that the Kalman filter-based IFB rate estimation algorithm is a satisfactory option for high-accuracy GLONASS positioning. Numéro de notice : A2017-620 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0660-3 En ligne : https://doi.org/10.1007/s10291-017-0660-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86930 [article]

Global ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS / Peng Chen in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 639 – 650 Titre : Global ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS Type de document : Article/Communication Auteurs : Peng Chen, Auteur ; Yi Bin Yao, Auteur ; Wanqiang Yao, Auteur Année de publication : 2017 Article en page(s) : pp 639 – 650 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] coordonnées GNSS [Termes IGN] données altimétriques [Termes IGN] données DORIS [Termes IGN] ionosphère [Termes IGN] modèle ionosphérique [Termes IGN] occultation du signal [Termes IGN] radiooccultation [Termes IGN] teneur verticale totale en électrons Résumé : (auteur) Global ionosphere maps (GIMs) provided by the global navigation satellite systems (GNSS) data are essential in ionospheric research as the source of the global vertical total electron content (VTEC). However, conventional GIMs experience lower accuracy and reliability from uneven distribution of GNSS tracking stations, especially in ocean areas with few tracking stations. The orbits of ocean altimetry satellite cover vast ocean areas and can directly provide VTEC at nadir with two different wavelengths of radio waves. Radio occultation observations and the beacons of Doppler orbitography and radio positioning integrated by satellite (DORIS) are evenly distributed globally. Satellite altimetry, radio occultation and DORIS can compensate GNSS data in ocean areas, allowing a more accurate and reliable GIMs to be formed with the integration of these observations. This study builds GIMs with temporal intervals of 2 h by the integration of GNSS, satellite altimetry, radio occultation and DORIS data. We investigate the integration method for multi-source data and used the data in May 2013 to validate the effectiveness of integration. Result shows that VTEC changes by −11.0 to −7.0 TECU after the integration of satellite altimetry, radio occultation and DORIS data. The maximum root mean square decreases by 5.5 TECU, and the accuracy of GIMs in ocean areas improves significantly. Numéro de notice : A2017-216 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0554-9 En ligne : http://dx.doi.org/10.1007/s10291-016-0554-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85089 [article]

A new computerized ionosphere tomography model using the mapping function and an application to the study of seismic-ionosphere disturbance / Jian Kong in Journal of geodesy, vol 90 n° 8 (August 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 8 (August 2016) . - pp 741 – 755 Titre : A new computerized ionosphere tomography model using the mapping function and an application to the study of seismic-ionosphere disturbance Type de document : Article/Communication Auteurs : Jian Kong, Auteur ; Yi Bin Yao, Auteur ; Lei Liu, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 741 – 755 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] altération [Termes IGN] correction troposphérique [Termes IGN] International Reference Ionosphere [Termes IGN] Japon [Termes IGN] séisme [Termes IGN] teneur totale en électrons [Termes IGN] tomographie [Termes IGN] troposphère Résumé : (auteur) A new algorithm for ionosphere tomography using the mapping function is proposed in this paper. First, the new solution splits the integration process into four layers along the observation ray, and then, the single-layer model (SLM) is applied to each integration part using a mapping function. Next, the model parameters are estimated layer by layer with the Kalman filtering method by introducing the scale factor (SF) γ to solve the ill-posed problem. Finally, the inversed images of different layers are combined into the final CIT image. We utilized simulated data from 23 IGS GPS stations around Europe to verify the estimation accuracy of the new algorithm; the results show that the new CIT model has better accuracy than the SLM in dense data areas and the CIT residuals are more closely grouped. The stability of the new algorithm is discussed by analyzing model accuracy under different error levels (the max errors are 5TECU, 10TECU, 15TECU, respectively). In addition, the key preset parameter, SFγ, which is given by the International Reference Ionosphere model (IRI2012). The experiment is designed to test the sensitivity of the new algorithm to SF variations. The results show that the IRI2012 is capable of providing initial SF values. Also in this paper, the seismic-ionosphere disturbance (SID) of the 2011 Japan earthquake is studied using the new CIT algorithm. Combined with the TEC time sequence of Sat.15, we find that the SID occurrence time and reaction area are highly related to the main shock time and epicenter. According to CIT images, there is a clear vertical electron density upward movement (from the 150-km layer to the 450-km layer) during this SID event; however, the peak value areas in the different layers were different, which means that the horizontal movement velocity is not consistent among the layers. The potential physical triggering mechanism is also discussed in this paper. Compared with the SLM, the RMS of the new CIT model is improved by 16.78%, while the CIT model could provide the three-dimensional variation in the ionosphere. Numéro de notice : A2016-504 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0906-9 En ligne : http://dx.doi.org/10.1007/s00190-016-0906-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81528 [article]

Improved one/multi-parameter models that consider seasonal and geographic variations for estimating weighted mean temperature in ground-based GPS meteorology / Yi Bin Yao in Journal of geodesy, vol 88 n° 3 (March 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 3 (March 2014) . - pp 273 - 282 Titre : Improved one/multi-parameter models that consider seasonal and geographic variations for estimating weighted mean temperature in ground-based GPS meteorology Type de document : Article/Communication Auteurs : Yi Bin Yao, Auteur ; Bao Zhang, Auteur ; Chaoqian Xu, Auteur ; Feng Yang, Auteur Année de publication : 2014 Article en page(s) : pp 273 - 282 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] données GPS [Termes IGN] météorologie [Termes IGN] pression atmosphérique [Termes IGN] propagation troposphérique [Termes IGN] signal GPS [Termes IGN] température [Termes IGN] température de surface [Termes IGN] vapeur d'eau Résumé : (Auteur) In ground-based GPS meteorology, weighted mean temperature is the key parameter to calculate the conversion factor which will be used to map zenith wet delay to precipitable water vapor. In practical applications, we can hardly obtain the vertical profiles of meteorological parameters over the site, thus cannot use the integration method to calculate weighted mean temperature. In order to exactly calculate weighted mean temperature from a few meteorological parameters, this paper studied the relation between weighted mean temperature and surface temperature, surface water vapor pressure and surface pressure, and determined the relationship between, on the one hand, the weighted mean temperature, and, on the other hand, the surface temperature and surface water vapor pressure. Considering the seasonal and geographic variations in the relationship, we employed the trigonometry functions with an annual cycle and a semi-annual cycle to fit the residuals (seasonal and geographic variations are reflected in the residuals). Through the above work, we finally established the GTm-I model and the PTm-I model with a 2 2.5 (latlon) resolution. Test results show that the two models both show a consistent high accuracy around the globe, which is about 1.0 K superior to the widely used Bevis weighted mean temperature–surface temperature relationship in terms of root mean square error. Numéro de notice : A2014-136 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0684-6 Date de publication en ligne : 05/12/2013 En ligne : https://doi.org/10.1007/s00190-013-0684-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33041 [article]

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Global empirical model for mapping zenith wet delays onto precipitable water / Yi Bin Yao in Journal of geodesy, vol 87 n° 5 (May 2013)  

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