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GNSS carrier phase time-variant observable-specific signal bias (OSB) handling: an absolute bias perspective in multi-frequency PPP / Ke Su in GPS solutions, vol 26 n° 3 (July 2022)  

Public [article]  inGPS solutions > vol 26 n° 3 (July 2022) . - n° 71 Titre : GNSS carrier phase time-variant observable-specific signal bias (OSB) handling: an absolute bias perspective in multi-frequency PPP Type de document : Article/Communication Auteurs : Ke Su, Auteur ; Shuanggen Jin, Auteur ; Guoqiang Jiao, Auteur Année de publication : 2022 Article en page(s) : n° 71 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur de phase [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] signal BeiDou [Termes IGN] signal Galileo [Termes IGN] temps de convergence Résumé : (auteur) In precise satellite clock estimation, the satellite clock offsets absorb the pseudorange and carrier phase time-variant hardware delays. The dissimilarity of the satellite clock estimated with observations at different frequencies is termed the inter-frequency clock bias (IFCB). The bias inconsistency suggests that the simple ionospheric-free satellite clock cannot directly be applied to the multi-frequency carrier phase observations in multi-frequency precise point positioning (PPP). We propose the carrier phase time-variant observable-specific signal bias (OSB) concept and the corresponding estimation approach to solve this. The definition, rationality, reliability and validity of the carrier phase time-variant OSB are clarified. The new concept advantage is that a set of the carrier phase time-variant OSB values can directly amend on the carrier phase observations, and thereafter, the IFCB effect can be eliminated, which provides the flexibilities for the GNSS carrier phase observation handing. Datasets collected from 144 Multi-GNSS Experiment (MGEX) stations are adopted for the carrier phase time-variant OSB estimation and an analysis of its effect on the GNSS multi-frequency PPP performance. The various multi-frequency PPP models are tested and evaluated considering the carrier phase time-variant OSB correction. The results indicate that the GPS, BDS-2 and BDS-3 carrier phase time-variant OSB time series have the obvious amplitudes and the amplitudes of the Galileo and QZSS carrier phase time-variant OSB are small. The GPS and BDS-2 multi-frequency PPP performance is significantly enhanced when correcting the carrier phase time-variant OSB. The GPS-only kinematic ionospheric-float PPP exhibits the positioning accuracy of 1.0 cm, 2.2 cm and 2.6 cm in the north, east and up components when correcting the carrier phase time-variant OSB, whereas the positioning accuracy of the case without the correction is 1.4 cm, 2.8 cm and 3.7 cm in three directions, respectively. The mean convergence time of two dual-frequency and three triple-frequency BDS-2-only kinematic PPP is reduced by 5.0%, 4.9%, 5.4%, 4.7% and 4.6%, respectively, with the carrier phase time-variant OSB correction. The carrier phase time-variant OSB improvement on BDS-3-only multi-frequency PPP is not obvious owing to the relatively few available and stable carrier phase time-variant OSB values. The reliability, suitability and effectiveness of the GNSS carrier phase time-variant OSB are demonstrated. Numéro de notice : A2022-360 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01255-x Date de publication en ligne : 22/04/2022 En ligne : https://doi.org/10.1007/s10291-022-01255-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100579 [article]

Multi-view urban scene classification with a complementary-information learning model / Wanxuan Geng in Photogrammetric Engineering & Remote Sensing, PERS, vol 88 n° 1 (January 2022)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 88 n° 1 (January 2022) . - pp 65 - 72 Titre : Multi-view urban scene classification with a complementary-information learning model Type de document : Article/Communication Auteurs : Wanxuan Geng, Auteur ; Weixun Zhou, Auteur ; Shuanggen Jin, Auteur Année de publication : 2022 Article en page(s) : pp 65 - 72 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] apprentissage automatique [Termes IGN] classification par séparateurs à vaste marge [Termes IGN] données de terrain [Termes IGN] données multisources [Termes IGN] extraction de traits caractéristiques [Termes IGN] fusion de données multisource [Termes IGN] image aérienne [Termes IGN] niveau du sol [Termes IGN] précision de la classification [Termes IGN] scène urbaine Résumé : (Auteur) Traditional urban scene-classification approaches focus on images taken either by satellite or in aerial view. Although single-view images are able to achieve satisfactory results for scene classification in most situations, the complementary information provided by other image views is needed to further improve performance. Therefore, we present a complementary information-learning model (CILM) to perform multi-view scene classification of aerial and ground-level images. Specifically, the proposed CILM takes aerial and ground-level image pairs as input to learn view-specific features for later fusion to integrate the complementary information. To train CILM, a unified loss consisting of cross entropy and contrastive losses is exploited to force the network to be more robust. Once CILM is trained, the features of each view are extracted via the two proposed feature-extraction scenarios and then fused to train the support vector machine classifier for classification. The experimental results on two publicly available benchmark data sets demonstrate that CILM achieves remarkable performance, indicating that it is an effective model for learning complementary information and thus improving urban scene classification. Numéro de notice : A2022-063 Affiliation des auteurs : non IGN Thématique : IMAGERIE/URBANISME Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.14358/PERS.21-00062R2 Date de publication en ligne : 01/01/2022 En ligne : https://doi.org/10.14358/PERS.21-00062R2 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99708 [article]

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Roles of horizontal and vertical tree canopy structure in mitigating daytime and nighttime urban heat island effects / Jike Chen in International journal of applied Earth observation and geoinformation, vol 89 (July 2020)  

Public [article]  inInternational journal of applied Earth observation and geoinformation > vol 89 (July 2020) . - n° 102060 Titre : Roles of horizontal and vertical tree canopy structure in mitigating daytime and nighttime urban heat island effects Type de document : Article/Communication Auteurs : Jike Chen, Auteur ; Shuanggen Jin, Auteur ; Peijun Du, Auteur Année de publication : 2020 Article en page(s) : n° 102060 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] arbre urbain [Termes IGN] canopée [Termes IGN] carte de la végétation [Termes IGN] couvert forestier [Termes IGN] données lidar [Termes IGN] ilot thermique urbain [Termes IGN] modèle numérique de terrain [Termes IGN] Nankin (Kiangsou) [Termes IGN] occupation du sol [Termes IGN] régression linéaire [Termes IGN] semis de points [Termes IGN] température au sol Résumé : (auteur) The urban heat island (UHI) is increasingly recognized as a serious, worldwide problem because of urbanization and climate change. Urban vegetation is capable of alleviating UHI and improving urban environment by shading together with evapotranspiration. While the impacts of abundance and spatial configuration of vegetation on land surface temperature (LST) have been widely examined, very little attention has been paid to the role of vertical structure of vegetation in regulating LST. In this study, we investigated the relationships between horizontal/vertical structure characteristics of urban tree canopy and LST as well as diurnal divergence in Nanjing City, China, with the help of high resolution vegetation map, Light Detection and Ranging (LiDAR) data and various statistical analysis methods. The results indicated that composition, configuration and vertical structure of tree canopy were all significantly related to both daytime LST and nighttime LST. Tree canopy showed stronger influence on LST during the day than at night. Note that the contribution of composition of tree canopy to explaining spatial heterogeneity of LST, regardless of day and night, was the highest, followed by vertical structure and configuration. Combining composition, configuration and vertical structure of tree canopy can take advantage of their respective advantages, and best explain variation in both daytime LST and nighttime LST. As for the independent importance of factors affecting spatial variation of LST, percent cover of tree canopy (PLAND), mean tree canopy height (TH_Mean), amplitude of tree canopy height (TA) and patch cohesion index (COHESION) were the most influential during the day, while the most important variables were PLAND, maximum height of tree canopy (TH_Max), variance of tree canopy height (TH_SD) and COHESION at night. This research extends our understanding of the impacts of urban trees on the UHI effect from the horizontal to three-dimensional space. In addition, it may offer sustainable and effective strategies for urban designers and planners to cope with increasing temperature. Numéro de notice : A2020-715 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.1016/j.jag.2020.102060 Date de publication en ligne : 25/02/2020 En ligne : https://doi.org/10.1016/j.jag.2020.102060 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96285 [article]

Co-seismic displacement and waveforms of the 2018 Alaska earthquake from high-rate GPS PPP velocity estimation / Shuanggen Jin in Journal of geodesy, vol 93 n° 9 (September 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 9 (September 2019) . - pp 1559 - 1569 Titre : Co-seismic displacement and waveforms of the 2018 Alaska earthquake from high-rate GPS PPP velocity estimation Type de document : Article/Communication Auteurs : Shuanggen Jin, Auteur ; Ke Su, Auteur Année de publication : 2019 Article en page(s) : pp 1559 - 1569 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Alaska (Etats-Unis) [Termes IGN] déformation de la croute terrestre [Termes IGN] positionnement cinématique [Termes IGN] positionnement ponctuel précis [Termes IGN] séisme [Termes IGN] vitesse de déplacement Résumé : (Auteur) For earthquake and tsunami early warning and emergency response, the parameters of earthquakes should be determined rapidly and correctly. The precise displacement time series can be obtained from high-rate GPS precise point positioning (PPP) during the earthquake, but require long convergence time. In this paper, the PPP velocity estimation (PPPVE) approach is applied to estimate the velocity waveforms and integrate to displacement waveforms in real-time scenarios. A case study of the 2018 Alaska earthquake is conducted from 1 Hz GPS data. The accuracy of velocity and displacement waveforms for 1 Hz GPS data is analyzed by comparing PPPVE-derived displacements with kinematic PPP solution. The results indicate that PPP and PPPVE are both capable of detecting seismic displacement waveforms with amplitude of 1 cm horizontally, while PPPVE can detect the displacement waveforms with much faster convergence speed. The mean convergence time of PPPVE for north, east and up components are 19, 22 and 31 s, respectively. The derived ground motion parameters estimate a magnitude of Mw = 7.97 ± 0.18, showing a great consistency and agreement with the seismometer magnitude. The preliminary relationship between the seismic intensity and ground motion parameters is established and evaluated for an auxiliary reference. Furthermore, the permanent displacement induced by the earthquake is obtained from real-time PPPVE approach. The benefits of PPPVE approach for GNSS seismology are demonstrated. Numéro de notice : A2019-506 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-019-01269-3 Date de publication en ligne : 24/06/2019 En ligne : https://doi.org/10.1007/s00190-019-01269-3 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93789 [article]