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Validation of Island 3D-mapping based on UAV spatial point cloud optimization: a case study in Dongluo Island of China / Jian Wu in Photogrammetric Engineering & Remote Sensing, PERS, vol 89 n° 3 (March 2023)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 89 n° 3 (March 2023) . - pp 173 - 182 Titre : Validation of Island 3D-mapping based on UAV spatial point cloud optimization: a case study in Dongluo Island of China Type de document : Article/Communication Auteurs : Jian Wu, Auteur ; Shifeng Fu, Auteur ; Peng Chen, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : pp 173 - 182 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] cartographie 3D [Termes IGN] Chine [Termes IGN] île [Termes IGN] image captée par drone [Termes IGN] modélisation 3D [Termes IGN] semis de points [Termes IGN] télédétection aérienne Résumé : (Auteur) The unmanned aerial vehicle (UAV) remote sensing is of small volume, low cost, fine timeliness, and high spatial resolution, and has the special advantage on island surveying. Focus on the inaccurate elevation of non-ground point cloud without lidar device, this study explored a methodology for island three-dimensional (3D) mapping and modelling based on spatial point clouds optimization with a K-Nearest Neighbors Adaptive Inverse Distance Weighted (K-AIDW) interpolation algorithm. By classifying the UAV point clouds into ground, vegatetation, and structure, the K-AIDW algorithm was applied to optimize the elevations of non-ground point clouds (vegetation and structure) to recalculate Z values. The aerophotogrammetry result was generated based on the optimized spatial point clouds. Finally, the 3D model of Dongluo Island was reconstructed and rendered in Metashape. The accuracy evaluation result shows that the max-errors of ground control points (–0.0154 in X, 0.0305 in Y, and 0.0133 in Z) and the checkpoints (–0.091 in X, –0.176 in Y, and 0.338 in Z) can meet the error-tolerance requirements of the corresponding terrain on the 1:500 scale set by the national standard of GB/T 23236-2009 in China. It is found that the K-AIDW algorithm displayed the best Z accuracy (root-mean-square error of 0.2538) compared with IDW (0.3668) and no-optimized (1.6012), proving it is an effective methodology for improving 3D-modelling accuracy of island. Numéro de notice : A2023-172 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.14358/PERS.22-00109R2 Date de publication en ligne : 01/03/2023 En ligne : https://doi.org/10.14358/PERS.22-00109R2 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102923 [article]

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A novel ionospheric mapping function modeling at regional scale using empirical orthogonal functions and GNSS data / Peng Chen in Journal of geodesy, vol 96 n° 5 (May 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 5 (May 2022) . - n° 34 Titre : A novel ionospheric mapping function modeling at regional scale using empirical orthogonal functions and GNSS data Type de document : Article/Communication Auteurs : Peng Chen, Auteur ; Rong Wang, Auteur ; Zhihao Wang, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 34 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] décomposition en fonctions orthogonales empiriques [Termes IGN] données GNSS [Termes IGN] ionosphère [Termes IGN] modèle ionosphérique [Termes IGN] série temporelle [Termes IGN] teneur totale en électrons [Termes IGN] teneur verticale totale en électrons Résumé : (auteur) The ionospheric mapping function (MF) converts the line-of-sight slant total electron content (STEC) into the vertical total electron content (VTEC) and vice versa, and it is an important function in the creation and use of ionospheric models. Most of the existing MFs are only related to satellite elevation angle, the accuracy is low, and it is necessary to establish a MF with higher accuracy. Therefore, this paper considers the differences of MF for different local time (LT) and DOY (day of year), and uses the Global Navigation Satellite Systems (GNSS) STEC observation data from International GNSS Service (IGS) tracking stations in the northern hemisphere mid-latitude region in 2016–2020 to establish a novel MF model. First, we retrieve the mapping coefficient αh for different LT and DOY, where the results show significant correlation with LT and DOY, and other periodic variations. Then, we use the empirical orthogonal functions (EOF) to decompose the time series, and the first four order EOF components can describe 98.31% of the total variability. Finally, the periodic function is used to fit the time series of EOF, and a small number of model coefficients are obtained. This work employs the differential STEC of 28 IGS tracking stations in the mid-latitudes of the northern hemisphere in 2020 to verify the accuracy of the new MF and compare it with the widely used modified single-layer model (MSLM) MF. The results show that the accuracy of the new MF is higher than the existing MSLM MF when using JPLG (Jet Propulsion Laboratory’s final Global Ionospheric Maps) to convert VTEC to STEC. Compared with MSLM MF, the RMS of the new MF is reduced by 0.24 TECU on average, and the maximum reduction is close to 0.4 TECU (~ 25%). Among the 28 tracking stations that participated in the verification, the new MF is better than MSLM MF on most days, with 7 stations reaching 100% and 20 stations exceeding 95%. For nearly 60% of the days in 2020, the accuracy of the new MF for all tracking stations is better than that of MSLM MF. Numéro de notice : A2022-340 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01624-x Date de publication en ligne : 30/04/2022 En ligne : https://doi.org/10.1007/s00190-022-01624-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100512 [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]