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Assessment of the positioning performance and tropospheric delay retrieval with precise point positioning using products from different analysis centers / Feng Zhou in GPS solutions, vol 24 n° 1 (January 2020)  

Public [article]  inGPS solutions > vol 24 n° 1 (January 2020) Titre : Assessment of the positioning performance and tropospheric delay retrieval with precise point positioning using products from different analysis centers Type de document : Article/Communication Auteurs : Feng Zhou, Auteur ; Xinyun Cao, Auteur ; Yulong Ge, Auteur ; Weiwei Li, Auteur Année de publication : 2020 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] distance zénithale [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] propagation troposphérique [Termes IGN] retard troposphérique [Termes IGN] temps de convergence Résumé : (Auteur) The performance of precise point positioning (PPP) strongly depends on the quality of satellite orbit and clock products. To give a full evaluation of PPP performance with the various publicly available precise satellite orbit and clock products, this contribution comprehensively investigates the positioning performance as well as tropospheric delay retrieval of GPS-, GLONASS-, and Galileo-only PPP with the precise products from eight International GNSS Service (IGS) (i.e., cod, emr, esa, gfz, grg, igs, jpl, and mit) and five multi-GNSS experiment (MGEX) analysis centers (ACs) (i.e., com, gbm, grm, jax, and wum) based on the observations of 90 MGEX tracking stations in a 1-month period (April 2019). The positioning performance in terms of convergence time and positioning accuracy is assessed by coordinate-static and coordinate-kinematic PPP modes, while the tropospheric delay estimation in terms of accuracy is evaluated by coordinate-fixed PPP mode. For GPS- and GLONASS-only PPP with different AC products, the positioning performances are comparable with each other except that with emr, jpl, mit, and jax products. Overall, the positioning performance with cod and com products provided by CODE ranks the first. For Galileo-only PPP, the grm product performs the best. For ZTD estimation, the accuracy derived from GPS-, GLONASS-, and Galileo-only solutions agrees well and the differences in accuracy among different AC products can be negligible. Numéro de notice : A2020-022 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-019-0925-0 Date de publication en ligne : 19/11/2019 En ligne : https://doi.org/10.1007/s10291-019-0925-0 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94463 [article]

Influence of stochastic modeling for inter-system biases on multi-GNSS undifferenced and uncombined precise point positioning / Feng Zhou in GPS solutions, vol 23 n° 3 (July 2019)  

Public [article]  inGPS solutions > vol 23 n° 3 (July 2019) Titre : Influence of stochastic modeling for inter-system biases on multi-GNSS undifferenced and uncombined precise point positioning Type de document : Article/Communication Auteurs : Feng Zhou, Auteur ; Danan Dong, Auteur ; Xin Li, Auteur ; Harald Schuh, Auteur Année de publication : 2019 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] bruit blanc [Termes IGN] décalage d'horloge [Termes IGN] erreur systématique inter-systèmes [Termes IGN] estimation statistique [Termes IGN] modèle stochastique [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis Résumé : (auteur) The focus of this study is on proper modeling of the dynamics for inter-system biases (ISBs) in multi-constellation Global Navigation Satellite System (GNSS) precise point positioning (PPP) processing. First, the theoretical derivation demonstrates that the ISBs originate from not only the receiver-dependent hardware delay differences among different GNSSs but also the receiver-independent time differences caused by the different clock datum constraints among different GNSS satellite clock products. Afterward, a comprehensive evaluation of the influence of ISB stochastic modeling on undifferenced and uncombined PPP performance is conducted, i.e., random constant, random walk process, and white noise process are considered. We use data based on a 1-month period (September 2017) Multi-GNSS Experiment (MGEX) precise orbit and clock products from four analysis centers (CODE, GFZ, CNES, and WHU) and 160 MGEX tracking stations. The results demonstrate that generally, the positioning performance of PPP in terms of convergence time and positioning accuracy with the final products from CODE, CNES, and WHU is comparable among the three ISB handling schemes. However, estimating ISBs as random walk process or white noise process outperforms that as the random constant when using the GFZ products. These results indicate that the traditional estimation of ISBs as the random constant may not always be reasonable in multi-GNSS PPP processing. To achieve more reliable positioning results, it is highly recommended to consider the ISBs as random walk process or white noise process in multi-GNSS PPP processing. Numéro de notice : A2019-199 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-019-0852-0 Date de publication en ligne : 09/04/2019 En ligne : https://doi.org/10.1007/s10291-019-0852-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92654 [article]

Enhancing real-time precise point positioning time and frequency transfer with receiver clock modeling / Yulong Ge in GPS solutions, vol 23 n° 1 (January 2019)  

Public [article]  inGPS solutions > vol 23 n° 1 (January 2019) Titre : Enhancing real-time precise point positioning time and frequency transfer with receiver clock modeling Type de document : Article/Communication Auteurs : Yulong Ge, Auteur ; Feng Zhou, Auteur ; Tianjun Liu, Auteur ; et al., Auteur Année de publication : 2019 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] horloge du récepteur [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] temps réel [Termes IGN] variance d'Allan Résumé : (Auteur) Thanks to the international GNSS service (IGS), which has provided an open-access real-time service (RTS) since 2013, real-time precise point positioning (RT-PPP) has become a major topic in the time community. Currently, a few scholars have studied RT-PPP time transfer, and the correlation of the receiver clock offsets between adjacent epochs have not been considered. We present a receiver clock offset model that considers the correlation of the receiver clock offsets between adjacent epochs using an a priori value. The clock offset is estimated using a between-epoch constraint model rather than a white noise model. This approach is based on two steps. First, the a priori noise variance is based on the Allan variance of the receiver clock offset derived from GPS PPP solutions with IGS final products. Second, by applying the between-epoch constraint model, the RT-PPP time transfer is achieved. Our numerical analyses clarify how the approach performs for RT-PPP time and frequency transfer. Based on five commonly used RTS products and six IGS stations, two conclusions are obtained straightforwardly. First, all RT-PPP solutions with different real-time products are capable of time transfer. The standard deviation (STD) values of the clock difference between the PPP solutions with respect to the IGS final clock products are less than 0.3 ns. Second, the STD values are reduced significantly by applying our approach. The reduction percent of STD values ranges from 4.0 to 35.5%. Moreover, the largest improvement ratio of frequency stability is 12 as compared to the solution of the white noise model. Note that the receiver clock offset from IGS final clock products is regarded as a reference. Numéro de notice : A2019-052 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-018-0814-y Date de publication en ligne : 19/12/2018 En ligne : https://doi.org/10.1007/s10291-018-0814-y Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92081 [article]

Narrow-band interference suppresion for SAR based on independent component analysis / Feng Zhou in IEEE Transactions on geoscience and remote sensing, vol 51 n° 10 (October 2013)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 51 n° 10 (October 2013) . - pp 4952 - 4960 Titre : Narrow-band interference suppresion for SAR based on independent component analysis Type de document : Article/Communication Auteurs : Feng Zhou, Auteur ; Mingliang Tao, Auteur ; Xueru Bai, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 4952 - 4960 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] analyse en composantes indépendantes [Termes IGN] brouillage [Termes IGN] écho radar [Termes IGN] image radar moirée [Termes IGN] interférence [Termes IGN] seuillage d'image Résumé : (Auteur) The narrow-band interference (NBI) is a common jamming signal against synthetic aperture radar (SAR), which can degrade the imaging quality severely. This paper proposes a new method for NBI suppression in the data domain based on the independent component analysis (ICA). In this method, echoes contaminated by the NBI are identified in the frequency domain. Next, time filtering and whitening are performed to the identified echoes. Then, the ICA is carried out to decompose the echoes into a series of basis signals, and the jamming components are selected by thresholding. Finally, the NBI is reconstructed and subtracted from the echoes, and the well-focused SAR imagery is obtained by conventional imaging methods. The proposed method copes well with the time-varying NBI with little signal loss. Results of simulated and measured data have proved the validity of the proposed method. Numéro de notice : A2013-600 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2013.2244605 En ligne : https://doi.org/10.1109/TGRS.2013.2244605 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32736 [article]

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