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Forest height retrieval using P-band airborne multi-baseline SAR data: A novel phase compensation method / Hongliang Lu in ISPRS Journal of photogrammetry and remote sensing, vol 175 (May 2021)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 175 (May 2021) . - pp 99 - 118 Titre : Forest height retrieval using P-band airborne multi-baseline SAR data: A novel phase compensation method Type de document : Article/Communication Auteurs : Hongliang Lu, Auteur ; Heng Zhang, Auteur ; Huaitao Fan, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 99 - 118 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] bande P [Termes IGN] Chine [Termes IGN] compensation [Termes IGN] données TomoSAR [Termes IGN] erreur de mesure [Termes IGN] erreur de phase [Termes IGN] Guyane (département français) [Termes IGN] hauteur des arbres [Termes IGN] image radar moirée [Termes IGN] ligne de base [Termes IGN] polarisation [Termes IGN] tomographie radar [Termes IGN] triangulation de Delaunay Résumé : (auteur) Synthetic aperture radar (SAR) tomography (TomoSAR) has been well-established for three-dimensional (3-D) information extraction of forests using the multi-baseline SAR data stacks. The multi-baseline SAR data stacks can be acquired by spaceborne and airborne SAR systems, but for forest scenarios, the data stacks acquired by the airborne SAR system are mostly used. Such a data stack has the advantages of short revisiting time and weak temporal decorrelation. However, due to the baseline errors (caused by the residual platform motion and the measurement errors of the navigation instruments), phase errors (PEs) will occur. PEs are independent of one track to the other, resulting in spreading and defocusing in tomographic imaging. In this paper, we proposed a novel phase compensation method named NC-PGA, which combines the methods of network construction (NC) and phase gradient autofocus (PGA) to estimate and compensate the PEs. The NC method uses the Delaunay triangulation network and beamforming to obtain an accurate elevation estimate of the selected permanent scatterers, which can be used as the prior information for subsequent processing to overcome the shortcomings of the PGA method in PEs estimation. The PGA method uses the spatial invariance of PEs in a limited area to compensate for the PE of each track. The applicability of the NC-PGA method is demonstrated using simulated data and real data. The real data contains two data stacks. The one is acquired by a full-polarization P-band airborne SAR system (developed independently by our project research team) over the study area in Saihanba Forest Farm in Hebei, China. The other one is acquired by ONERA SETHI airborne system over Paracou, French Guiana, in the frame of the European Space Agency’s campaign TropiSAR. We select a test area in the study area and successfully retrieve the height of the forest, and use LiDAR data for results validation and evaluation. Numéro de notice : A2021-271 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2021.02.022 date de publication en ligne : 14/03/2021 En ligne : https://doi.org/10.1016/j.isprsjprs.2021.02.022 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97329 [article]

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Impact of the third frequency GNSS pseudorange and carrier phase observations on rapid PPP convergences / Jiang Guo in GPS solutions, vol 25 n° 2 (April 2021)  

Public [article]  inGPS solutions > vol 25 n° 2 (April 2021) . - 12 p. Titre : Impact of the third frequency GNSS pseudorange and carrier phase observations on rapid PPP convergences Type de document : Article/Communication Auteurs : Jiang Guo, Auteur ; Jianghui Geng, Auteur ; Chen Wang, Auteur Année de publication : 2021 Article en page(s) : 12 p. Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] bruit (théorie du signal) [Termes IGN] fréquence multiple [Termes IGN] ligne de base [Termes IGN] mesurage de pseudo-distance [Termes IGN] modèle fonctionnel [Termes IGN] modèle stochastique [Termes IGN] phase [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] signal BeiDou [Termes IGN] signal Galileo [Termes IGN] signal GNSS [Termes IGN] temps de convergence Résumé : (Auteur) New GNSS signals have significantly augmented positioning service and promoted algorithmic innovations such as rapid PPP convergence. With the emerging of multifrequency signals, it becomes essential to thoroughly explore the contribution of third frequency pseudorange and carrier phase toward PPP. In this study, we research the role of the third frequency observations on accelerating PPP convergence, commencing from both stochastic and functional models. We first constructed the stochastic model depending on the observation noise and then introduced two uncombined functional models with respect to different inter-frequency bias (IFB) estimation strategies. The double-differenced residuals based on a zero baseline were used to evaluate the signal noises, which were 0.09, 0.07, 0.11, 0.01 and 0.09 m for Galileo E1/E5a/E5b/E5/E6 pseudorange and 0.24, 0.31 and 0.05 m for BeiDou B1/B2/B3. Besides, carrier phase observations E5a/E5/E6/B1I/B3I shared a comparable signal noise of 0.002 m, while the signal noises of E1/E5b/B2I were 0.003 m. Both BeiDou-2/Galileo and Galileo-only float PPP were implemented based on the dataset collected from 25 stations, spanning 30 days. Triple-frequency Galileo PPP achieved convergence successfully in 19.9 min if observations were weighted according to observation precision, showing a comparable performance of dual-frequency PPP. Meanwhile, the convergence time of triple-frequency float PPP was further shortened to 19.2 min when satellite pair IFBs were eliminated by estimating a second satellite clock. While the improvement of triple-frequency float PPP was marginal, triple-frequency PPP-AR using signals E1/E5a/E6 shortened the initialization time of the dual-frequency counterpart by 38%. Moreover, the performance of triple-frequency PPP-AR kept almost unchanged after we excluded the third frequency pseudorange observations. We thus suggest that the contribution of the third frequency to PPP mainly rests on ambiguity resolution, favored by the additional carrier phase observations. Numéro de notice : A2021-090 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01079-7 date de publication en ligne : 10/01/2021 En ligne : https://doi.org/10.1007/s10291-020-01079-7 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96875 [article]

Stochastic model reliability in GNSS baseline solution / Aviram Borko in Journal of geodesy, vol 95 n° 2 (February 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 2 (February 2021) . - n° 20 Titre : Stochastic model reliability in GNSS baseline solution Type de document : Article/Communication Auteurs : Aviram Borko, Auteur ; Gilad Even-Tzur, Auteur Année de publication : 2021 Article en page(s) : n° 20 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] données GNSS [Termes IGN] double différence [Termes IGN] fiabilité des données [Termes IGN] ligne de base [Termes IGN] matrice de covariance [Termes IGN] modèle stochastique [Termes IGN] résolution d'ambiguïté [Termes IGN] test statistique [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) GNSS observations stochastic model influences all subsequent stages of data processing, from the possibility to reach the optimal parameters estimation, to the reliability and quality control of the solution. Nowadays, an uncontrolled use of GNSS stochastic models is common for both data processing and simulation missions, especially in commercial GNSS software packages. As a result, the variance–covariance matrices that are derived in the processing are inadequate and cause incorrect interpretations of the results. A proper method to evaluate the reliability of the stochastic model is needed to reflect the confidence level in statistic testing and simulation mission efforts. In this contribution, a novel method for evaluating the statistical nature of GNSS stochastic model is presented. The method relies on the deterministic nature of the integer ambiguity variable to examine and express the expected multinormal distribution of the double-difference adjustment results. The suggested method was used with a controlled experiment and 24 h of observations data to investigate how the statistical nature of the stochastic model is affected by different baseline lengths. The results indicate that as the baseline length increases, the stochastic model is less predictable and exposed to irregularities in the observation’s precision. Additionally, the reliability of the integer ambiguity resolution success rate (SR) was tested as part of the stochastic model evaluation. The results show a dramatic degradation in the SR prediction level when using an inadequate stochastic model, which suggests using extra caution when handling this parameter unless high-confidence reliable stochastic model is available. Numéro de notice : A2021-136 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01472-1 date de publication en ligne : 31/01/2021 En ligne : https://doi.org/10.1007/s00190-021-01472-1 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97009 [article]

Application of baseline constraint Kalman filter to BeiDou precise point positioning / Xiaoguo Guan in Survey review, vol 53 n°376 (January 2021)  

Public [article]  inSurvey review > vol 53 n°376 (January 2021) . - pp 55 - 69 Titre : Application of baseline constraint Kalman filter to BeiDou precise point positioning Type de document : Article/Communication Auteurs : Xiaoguo Guan, Auteur ; Hongzhou Chai, Auteur ; Guorui Xiao, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 55 - 69 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] filtre de Kalman [Termes IGN] géodésie marine [Termes IGN] ligne de base [Termes IGN] positionnement cinématique [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement ponctuel précis [Termes IGN] positionnement statique [Termes IGN] précision du positionnement Résumé : (auteur) This paper proposes a baseline constrained PPP method to enhance the performance. The approach is based on constrained Kalman filter, and applied to BeiDou PPP in static, pseudo-kinematic, real kinematic modes. Both zero baseline and short baseline constrained PPP are verified in static mode, while a marine geodesy environment is designed to evaluate the performance in kinematic mode. The experiment results show that, compared to the PPP without constraint, the baseline constrained PPP can significantly improve the positional accuracy. Furthermore, the accuracy of baseline constrained static PPP can reach centimetre level, while the kinematic PPP can reach decimetre level. Numéro de notice : A2021-049 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2019.1685197 date de publication en ligne : 07/11/2019 En ligne : https://doi.org/10.1080/00396265.2019.1685197 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96784 [article]

Integer-estimable GLONASS FDMA model as applied to Kalman-filter-based short- to long-baseline RTK positioning / Pengyu Hou in GPS solutions, Vol 24 n° 4 (October 2020)  

Public [article]  inGPS solutions > Vol 24 n° 4 (October 2020) . - 14 p. Titre : Integer-estimable GLONASS FDMA model as applied to Kalman-filter-based short- to long-baseline RTK positioning Type de document : Article/Communication Auteurs : Pengyu Hou, Auteur ; Baocheng Zhang, Auteur ; Teng Liu, Auteur Année de publication : 2020 Article en page(s) : 14 p. Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] compensation Lambda [Termes IGN] données GLONASS [Termes IGN] données GPS [Termes IGN] filtre de Kalman [Termes IGN] ionosphère [Termes IGN] ligne de base [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GLONASS [Termes IGN] résolution d'ambiguïté [Termes IGN] signal GLONASS Résumé : (auteur) Fast ambiguity resolution is a major challenge for GLONASS phase-based applications. The integer-estimable frequency-division multiple-access (IE-FDMA) model succeeds in formulating a set of estimable GLONASS phase ambiguities and preserving the integer property, to which the classical integer ambiguity resolution, typically the least-squares ambiguity decorrelation adjustment (LAMBDA), becomes readily applicable. The initial assessment of the IE-FDMA model demonstrated instantaneous ambiguity resolution capability in case of short-baseline real-time kinematic (RTK) positioning based on ionosphere-fixed formulation, in which the data processing strategy is window (batch)-based least-squares estimation with window length ranging from one to a few epochs. Here, we extend the applicability of the IE-FDMA model to Kalman-filter-based, ionosphere-fixed, ionosphere-weighted, and ionosphere-free cases, which are, respectively, adoptable for short-, medium-, and long-baseline RTK positioning. To adapt the IE-FDMA model to the Kalman filter, we estimate, at each epoch, first the estimable ambiguities, then transform them into integer-estimable ones, and finally resolve them into correct integers. This enables the rigorous integer ambiguity resolution and, at the same time, eases the recursive construction of integer-estimable ambiguities. We analyze global positioning system (GPS) and GLONASS data of nine baselines with lengths varying from several meters to more than one hundred kilometers. The results demonstrate the feasibility of fast ambiguity resolution not only for the GLONASS phase-only short-baseline RTK positioning, but for the GPS + GLONASS medium- and long-baseline RTK positioning as well. In all cases, the fixed solution with faster (several-minutes) convergence and higher (centimeter-level) precision indicates the benefits from GLONASS ambiguity resolution as compared to the float solution. Moreover, the dual-system solution with decreased ambiguity dilution of precision (ADOP) and improved positioning precision confirms the advantages of integrating GLONASS with GPS in contrast to the GPS-only situation. Numéro de notice : A2020-524 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01008-8 date de publication en ligne : 11/07/2020 En ligne : https://doi.org/10.1007/s10291-020-01008-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95699 [article]

Effect of spatial correlation on the performances of modernized GPS and Galileo in relative positioning / Noureddine Kheloufi in Geodesy and cartography, vol 46 n° 2 (July 2020)  

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Prognostic evaluation of the impact of restricted horizon visibility on the accuracy of position (coordinates) obtained with GNSS based on empirical data / Oleksandr Yanchuk in Geodesy and cartography, vol 46 n° 2 (July 2020)  

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Reducing multipath effect of low-cost GNSS receivers for monitoring by considering temporal correlations / Li Zhang in Journal of applied geodesy, vol 14 n° 2 (April 2020)  

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Calibration errors in determining slant Total Electron Content (TEC) from multi-GNSS data / Wei Li in Advances in space research, vol 63 n° 5 (1 March 2019)  

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Optimisation of GNSS networks, considering baseline correlations / M. Amin Alizadeh-Khameneh in Survey review, vol 51 n° 364 (January 2019)  

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RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications / Francesco Darugna (2019)

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Assessment of local GNSS baselines at co-location sites / Iván Herrera Pinzón in Journal of geodesy, vol 92 n° 9 (September 2018)  

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Amélioration des calculs GNSS à façon du SGN / Mathilde Kremp (2018) 

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Baseline and triangulation geometry in a standard plenoptic camera / Christopher Hahne in International journal of computer vision, vol 126 n° 1 (January 2018)  

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Bounding the integer bootstrapped GNSS baseline’s tail probability in the presence of stochastic uncertainty / Steven E. Langel in Journal of geodesy, vol 90 n° 11 (November 2016)  

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