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High accuracy terrestrial positioning based on time delay and carrier phase using wideband radio signals / Han Dun (2021)  

Public Titre : High accuracy terrestrial positioning based on time delay and carrier phase using wideband radio signals Type de document : Thèse/HDR Auteurs : Han Dun, Auteur Editeur : Delft [Pays-Bas] : Delft University of Technology Année de publication : 2021 Format : 21 x 30 cm ISBN/ISSN/EAN : 978-94-6384-258-7 Note générale : bibliographie Thèse présentée en vue de l'obtention du Doctorat de l'Université de Delft Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] centre de phase [Termes IGN] correction du trajet multiple [Termes IGN] interruption du signal [Termes IGN] méthode du maximum de vraisemblance (estimation) [Termes IGN] phase [Termes IGN] précision du positionnement [Termes IGN] signal GNSS [Termes IGN] zone urbaine Index. décimale : THESE Thèses et HDR Résumé : (auteur) Accurate position solutions are in high demand for many emerging applications. Global navigation satellite systems (GNSS), however, may not meet the required positioning performance, especially in urban environments, due to multipath and weak received power of the GNSS signal that can be easily blocked by surrounding objects. To achieve a high ranging precision and improve resolvability of unwanted reflections in urban areas, a large signal bandwidth is required. In this thesis, a terrestrial positioning system using a wideband radio signal is developed as a complement to the existing GNSS, which can provide a better ranging accuracy and higher received signal power, compared to GNSS. In the terrestrial positioning system presented in this thesis, a wideband ranging signal is implemented by means of a multiband orthogonal frequency division multiplexing (OFDM) signal. All transmitters are synchronized by time and frequency reference signals, which are optically distributed through the white-rabbit precision time protocol (WR-PTP). Like in GNSS, the to-be-positioned receiver is not synchronized to the transmitters. Positioning takes place through range measurements between a number of transmitters and the receiver. Time delay and carrier phase are to be estimated from the received radio signal, which propagated through a multipath channel. This estimation is done on the basis of the channel frequency response and using the maximum likelihood principle. To determine whether or not reflections need to be considered in the estimation model, a measure of dependence is introduced to evaluate the change of the precision (i.e., variance), and the measure of bias is introduced to assess the bias of the estimator when the reflection is not considered. Also, a methodology is proposed for sparsity-promoting ranging signal design in this thesis. Based on a multiband OFDM signal, ranging signal design comes to sparsely select as few signal bands as possible. Using fewer signal bands for ranging leads to less computational complexity in time delay and carrier phase estimation, while the ranging performance can still benefit from a large virtual signal bandwidth, which is defined by the entire bandwidth between the two signal bands at the spectral edges. It is proposed to use the Cramér-Rao lower bound (CRLB) of time delay estimation, the measure of dependence, and the measure of bias as constraints in ranging performance, and formulate an optimization problem to design a sparse multiband signal. Note de contenu : 1- Introduction 2- Multiband OFDM signal model 3- Time delay estimation 4- Carrier phase estimation 5- Signal design for positioning 6- Positioning models 7- Experimental results 8- Conclusions and recommendations Numéro de notice : 28694 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : Thèse de Doctorat : Mathematical Geodesy and Positioning : Delft : 2021 DOI : 10.4233/uuid:98a7f072-7423-4a23-ac9b-8b88540c260d En ligne : https://doi.org/10.4233/uuid:98a7f072-7423-4a23-ac9b-8b88540c260d Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100361

Polarimetric SAR calibration and residual error estimation when corner reflectors are unavailable / Lei Shi in IEEE Transactions on geoscience and remote sensing, vol 58 n° 6 (June 2020)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 58 n° 6 (June 2020) . - pp 4454 - 4471 Titre : Polarimetric SAR calibration and residual error estimation when corner reflectors are unavailable Type de document : Article/Communication Auteurs : Lei Shi, Auteur ; Pingxiang Li, Auteur ; Jie Yang, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 4454 - 4471 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] bruit (théorie du signal) [Termes IGN] coin réflecteur [Termes IGN] dégradation du signal [Termes IGN] données polarimétriques [Termes IGN] étalonnage [Termes IGN] extraction automatique [Termes IGN] image radar moirée [Termes IGN] interruption du signal [Termes IGN] polarimétrie radar [Termes IGN] polarisation croisée [Termes IGN] rétrodiffusion de Bragg Résumé : (auteur) In this article, we propose a polarimetric calibration (PolCal) algorithm to estimate the system crosstalk, cross-polarization (x-pol), and co-polarization (co-pol) channel imbalance (CI) when ground corner reflectors (CRs) are unavailable. The current PolCal process requires at least one trihedral CR to determine the co-pol CI. However, the deployment of ground CRs is costly and may even be impossible in some areas. To calibrate a polarimetric image without CRs, our proposed method automatically extracts the volume-dominated and Bragg-like pixels as a reference to estimate the crosstalk, x-pol, and co-pol CI values. Then, a first-order polynomial model is exploited to fit the co-pol CI to further improve calibration accuracy. In the experimental section, we demonstrate the effectiveness of our proposed method with data from two of China’s newly developed very high-resolution systems. The experiments confirmed that the proposed workflow can be considered as a feasible calibration scheme when the ground deployment of CRs is impossible, and it is also an effective analysis tool for the assessment of calibrated products. Numéro de notice : A2020-286 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2020.2964732 Date de publication en ligne : 20/01/2020 En ligne : https://doi.org/10.1109/TGRS.2020.2964732 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95109 [article]

INS/GNSS integration using recurrent fuzzy wavelet neural networks / Parisa Doostdar in GPS solutions, vol 24 n° 1 (January 2020)  

Public [article]  inGPS solutions > vol 24 n° 1 (January 2020) Titre : INS/GNSS integration using recurrent fuzzy wavelet neural networks Type de document : Article/Communication Auteurs : Parisa Doostdar, Auteur ; Jafar Keighobadi, Auteur ; Mohammad Ali Hamed, Auteur Année de publication : 2020 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] classification floue [Termes IGN] couplage GNSS-INS [Termes IGN] données GNSS [Termes IGN] filtre de Kalman [Termes IGN] interruption du signal [Termes IGN] ondelette [Termes IGN] réseau neuronal artificiel [Termes IGN] réseau neuronal récurrent [Termes IGN] vitesse [Vedettes matières IGN] Traitement de données GNSS Résumé : (Auteur) In recent years, aided navigation systems through combining inertial navigation system (INS) with global navigation satellite system (GNSS) have been widely applied to enhance the position, velocity, and attitude information of autonomous vehicles. In order to gain the accuracy of the aided INS/GNSS in GNSS gap intervals, a heuristic neural network structure based on the recurrent fuzzy wavelet neural network (RFWNN) is applicable for INS velocity and position error compensation purpose. During frequent access to GNSS data, the RFWNN should be trained as a highly precise prediction model equipped with the Kalman filter algorithm. Therefore, the INS velocity and position error data are obtainable along with the lost intervals of GNSS signals. For performance assessment of the proposed RFWNN-aided INS/GNSS, real flight test data of a small commercial unmanned aerial vehicle (UAV) were conducted. A comparison of test results shows that the proposed NN algorithm could efficiently provide high-accuracy corrections on the INS velocity and position information during GNSS outages. Numéro de notice : A2020-019 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-019-0942-z Date de publication en ligne : 23/12/2019 En ligne : https://doi.org/10.1007/s10291-019-0942-z Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94458 [article]

Low-frequency desert noise intelligent suppression in seismic data based on multiscale geometric analysis convolutional neural network / Yuxing Zhao 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 650 - 665 Titre : Low-frequency desert noise intelligent suppression in seismic data based on multiscale geometric analysis convolutional neural network Type de document : Article/Communication Auteurs : Yuxing Zhao, Auteur ; Yue Li, Auteur ; Baojun Yang, Auteur Année de publication : 2020 Article en page(s) : pp 650 - 665 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] algorithme de filtrage [Termes IGN] analyse multiéchelle [Termes IGN] classification par réseau neuronal convolutif [Termes IGN] désert [Termes IGN] enregistrement de données [Termes IGN] filtrage du bruit [Termes IGN] filtre passe-bande [Termes IGN] interruption du signal [Termes IGN] lutte contre le bruit [Termes IGN] rapport signal sur bruit [Termes IGN] reconstruction du signal [Termes IGN] séisme Résumé : (auteur) Existing denoising algorithms often need to meet some premise assumptions and applicable conditions, such as the signal-to-noise ratio (SNR) cannot be too low, and the noise needs to obey a specific distribution (such as Gaussian distribution) and to satisfy some properties (such as stationarity). For the desert noise that shares the same frequency band with the effective signal and has complex characteristics (nonlinear, nonstationary, and non-Gaussian), it is difficult to find a universally applicable method. In response to this problem, a multiscale geometric analysis (MGA) convolutional neural network (CNN) is proposed in this article. One of the most important features of the CNN is that it can extract data-rich intrinsic information from the training set without relying on a priori assumption. By introducing the CNN into the MGA, a new kind of denoising method can be created, which can achieve good results even under a low SNR. This article takes the nonsubsampled contourlet transform as an example to create a denoising network named NC-CNN for high-efficiency and intelligent denoising of desert seismic data. The processing results of synthetic seismic records and field seismic records prove that NC-CNN can effectively suppress the low-frequency noise (random noise and surface wave), and the effective signal almost has no energy loss. In addition, the reconstruction ability of the missing signals is also an advantage of this method. Numéro de notice : A2020-076 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2019.2938836 Date de publication en ligne : 24/09/2019 En ligne : https://doi.org/10.1109/TGRS.2019.2938836 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94608 [article]

Kalman-filter-based undifferenced cycle slip estimation in real-time precise point positioning / Pan Li in GPS solutions, vol 23 n° 4 (October 2019)  

Public [article]  inGPS solutions > vol 23 n° 4 (October 2019) Titre : Kalman-filter-based undifferenced cycle slip estimation in real-time precise point positioning Type de document : Article/Communication Auteurs : Pan Li, Auteur ; Xinyuan Jiang, Auteur ; Xiaohong Zhang, Auteur ; et al., Auteur Année de publication : 2019 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] filtre de Kalman [Termes IGN] glissement de cycle [Termes IGN] interruption du signal [Termes IGN] mesurage de phase [Termes IGN] modèle mathématique [Termes IGN] positionnement cinématique [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] station GLONASS [Termes IGN] station GPS [Termes IGN] temps réel Résumé : (Auteur) Global navigation satellite system (GNSS) precise point positioning (PPP) requires continuous carrier-phase observations to achieve a solution of high precision. Precisely correcting cycle slips caused by signal interruptions is crucial for recovering the data continuity. Most of the existing approaches usually employ only data of one epoch after the interruption for real-time cycle slip processing. In this study, we propose to introduce and estimate cycle slip parameters together with standard PPP parameters, such as position, ionospheric delay, and ambiguities in the case that possible cycle slips are detected, using a Kalman-filter-based procedure with the undifferenced and uncombined PPP model. The integer search strategy is used to fix cycle slips. To reduce the probability of wrong integer fixing, a strict integer validation threshold is suggested. As a result, it is not easy to fix all cycle slips with only one epoch of data. Our approach can be easily extended to use multi-epoch observations to enhance the cycle slip estimation. Once the cycle slips are correctly determined, continuous PPP can be achieved instantaneously. This new approach is tested and validated with three groups of experiments using GPS and GLONASS stations operated by the International GNSS Service from DOY 1–10, 2017, and a real vehicle kinematic data. Numerous experimental results showed that the proposed method can correctly fix the cycle slips for more than 99.5% of epochs suffering from re-convergence. On average, this method takes observation information from about 1.5–2.5 epochs to fix cycle slips and realize rapid re-convergence. Consequently, positioning performance is significantly improved. Numéro de notice : A2019-334 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-019-0894-3 Date de publication en ligne : 16/07/2019 En ligne : https://doi.org/10.1007/s10291-019-0894-3 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93423 [article]

Maintaining real-time precise point positioning during outages of orbit and clock corrections / Ahmed El-Mowafy in GPS solutions, vol 21 n° 3 (July 2017)  

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Efficient obstruction analysis for GNSS relative positioning of terrestrial mobile mapping system / J.Y. Han in Survey review, vol 47 n° 342 (May 2015)  

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GNSS and ionospheric scintillation: how to survive the next solar maximum / P. Kintner in Inside GNSS, vol 4 n° 4 (July - August 2009) 

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