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Resource-based growth models reveal opportunities to mitigate climate change effects on beech regeneration by silvicultural measures / Jan F. Wilkens in Forest ecology and management, vol 532 (March-15 2023)  

Public [article]  inForest ecology and management > vol 532 (March-15 2023) . - n° 120815 Titre : Resource-based growth models reveal opportunities to mitigate climate change effects on beech regeneration by silvicultural measures Type de document : Article/Communication Auteurs : Jan F. Wilkens, Auteur ; Robert Schlicht, Auteur ; Sven Wagner, Auteur Année de publication : 2023 Article en page(s) : n° 120815 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Europe (géographie politique) [Termes IGN] Fagus sylvatica [Termes IGN] gestion forestière [Termes IGN] modèle de croissance végétale [Termes IGN] rayonnement solaire [Termes IGN] régénération (sylviculture) [Termes IGN] semis (sylviculture) [Termes IGN] sylviculture [Vedettes matières IGN] Végétation et changement climatique Résumé : (auteur) Successful European beech (Fagus sylvatica L.) regeneration is both of great ecological and economical importance in European forest ecosystems and severely threatened by climate change impacts. To increase our knowledge of beech regeneration dynamics under climate change and the potential for controlling it through forest management, we studied interactive effects of solar radiation (PHAR), water and nutrient availability on the height growth of artificially (AR) and naturally regenerated (NR) beech seedlings. The study was conducted in the framework of experimental canopy gaps, under the influence of the 2018/19 drought and heatwaves. We measured PHAR by means of hemispherical photography, approximated water availability based on the inverse of modeled fine root density distributions of overstorey beech (BGRB) and oak (BGRO) and approximated nutrient availability based on soil fertility (SF), derived from forest site mapping. Results indicate that seedling resource availability and resulting growth responses increase with canopy gap size and vary among locations within the gap. Multiplicative non-linear mixed models suggest that AR and NR relative height growth (RI) was best explained by interactive effects of PHAR, BGRB, BGRO and SF, which reflect complementary resource use patterns of beech seedlings. At optimal resource availability, AR reached a potential RI of 174%, which is about 20% higher compared to NR. While the low light growth responses of AR and NR both reflect saturation at 5 to 15% PHAR, depending on individual size and the availability of the remaining resources, NR showed a higher RI than AR at intermediate and high PHAR levels in cases of limited BGR and SF. In contrast to AR, NR growth was affected to a lesser extent by SF and BGRB and not significantly affected by BGRO. These results suggest that overstorey oaks have a lower effect on water availability of beech seedlings than overstorey beeches. Additionally, NR showed higher tolerance to water and nutrient limitation than AR, probably due to better root system development. In conclusion, site-specific potential for mitigating the effects of climate change on beech regeneration through forest management lies in the adaptation of silvicultural systems, i.e., the creation of canopy gaps larger than 200 m2, thus significantly exceeding the average gap size of the natural disturbance regime, and the choice of the regeneration method. Numéro de notice : A2023-164 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1016/j.foreco.2023.120815 Date de publication en ligne : 26/01/2023 En ligne : https://doi.org/10.1016/j.foreco.2023.120815 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102869 [article]

Design and performance evaluation of a novel ranging signal based on an LEO satellite communication constellation / Jingfang Su in Geo-spatial Information Science, vol 26 n° 1 (March 2023)  

Public [article]  inGeo-spatial Information Science > vol 26 n° 1 (March 2023) . - pp 107 - 124 Titre : Design and performance evaluation of a novel ranging signal based on an LEO satellite communication constellation Type de document : Article/Communication Auteurs : Jingfang Su, Auteur ; Jia Su, Auteur ; Qingwu Yi, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : pp 107 - 124 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] bruit blanc [Termes IGN] orbite basse [Termes IGN] rapport signal sur bruit [Termes IGN] transformation de Fourier [Termes IGN] transformation inverse Résumé : (auteur) Driven by improvements in satellite internet and Low Earth Orbit (LEO) navigation augmentation, the integration of communication and navigation has become increasingly common, and further improving navigation capabilities based on communication constellations has become a significant challenge. In the context of the existing Orthogonal Frequency Division Multiplexing (OFDM) communication systems, this paper proposes a new ranging signal design method based on an LEO satellite communication constellation. The LEO Satellite Communication Constellation Block-type Pilot (LSCC-BPR) signal is superimposed on the communication signal in a block-type form and occupies some of the subcarriers of the OFDM signal for transmission, thus ensuring the continuity of the ranging pilot signal in the time and frequency domains. Joint estimation in the time and frequency domains is performed to obtain the relevant distance value, and the ranging accuracy and communication resource utilization rate are determined. To characterize the ranging performance, the Root Mean Square Error (RMSE) is selected as an evaluation criterion. Simulations show that when the number of pilots is 2048 and the Signal-to-Noise Ratio (SNR) is 0 dB, the ranging accuracy can reach 0.8 m, and the pilot occupies only 50% of the communication subcarriers, thus improving the utilization of communication resources and meeting the public demand for communication and location services. Numéro de notice : A2023-209 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/10095020.2022.2121229 Date de publication en ligne : 17/11/2022 En ligne : https://doi.org/10.1080/10095020.2022.2121229 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103136 [article]

Evaluation of strategies for the ultra-rapid orbit prediction of BDS GEO satellites / Wenxi Zhao in Geo-spatial Information Science, vol 26 n° 1 (March 2023)  

Public [article]  inGeo-spatial Information Science > vol 26 n° 1 (March 2023) . - pp 16 - 30 Titre : Evaluation of strategies for the ultra-rapid orbit prediction of BDS GEO satellites Type de document : Article/Communication Auteurs : Wenxi Zhao, Auteur ; Xiaolei Dai, Auteur ; Yidong Lou, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : pp 16 - 30 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] constellation BeiDou [Termes IGN] éclipse solaire [Termes IGN] orbite géostationnaire [Termes IGN] orbitographie [Termes IGN] rayonnement solaire Résumé : (auteur) The quality of BeiDou Navigation Satellite System (BDS) Geostationary Earth Orbit (GEO) ultra-rapid products is unsatisfactory because GEO satellites are nearly stationary relative to ground stations. To optimize the quality of these ultra-rapid orbit products, we investigated the effects of the fitting arc length, an a priori Solar-Radiation Pressure (SRP) model, and the along-track empirical acceleration on the prediction of BDS GEO satellite orbits. The predicted orbit arcs of 24-h were evaluated through comparisons with the corresponding observed orbit arc and Satellite Laser Ranging (SLR) observations. In both eclipse and non-eclipse seasons, accuracy of the orbit predictions obtained using a 48-h fitting arc length were better than those obtained using 24-h and 72-h fitting arc lengths. Although the overlapping precision of predicted orbits exhibited no obvious improvement when an a priori SRP model was employed, the systematic bias in the SLR residuals was significantly reduced. Specifically, the mean value of SLR residuals decreased from −0.248 m to −0.024 m during non-eclipse seasons and from −0.333 m to −0.041 m during eclipse seasons, respectively. In addition, when an empirical acceleration in the along-track direction was introduced, the three-Dimensional Root-Mean-Square (3D RMS) of overlapping orbits during eclipse seasons decreased from 2.964 to 1.080 m, which is comparable to that during non-eclipse seasons. Furthermore, the Standard Deviation (STD) of SLR residuals decreased from 0.419 to 0.221 m during eclipse seasons. The analysis of SRP estimates shows that the stability of SRP parameters was significantly enhanced after the introduction of along-track empirical acceleration in eclipse seasons. The optimal BDS GEO ultra-rapid orbit prediction products were yielded by using a 48-h fitting arc length, an a priori SRP model and an along-track empirical acceleration. Numéro de notice : A2023-182 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/10095020.2022.2071177 En ligne : https://doi.org/10.1080/10095020.2022.2071177 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102968 [article]

BDS-3 precise orbit and clock solution at Wuhan University: status and improvement / Jing Guo in Journal of geodesy, vol 97 n° 2 (February 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 2 (February 2023) . - n° 15 Titre : BDS-3 precise orbit and clock solution at Wuhan University: status and improvement Type de document : Article/Communication Auteurs : Jing Guo, Auteur ; Guo Chen, Auteur ; Xiaolong Xu, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 15 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] horloge du satellite [Termes IGN] orbite précise [Termes IGN] orbitographie [Termes IGN] positionnement par BeiDou [Termes IGN] rayonnement solaire [Termes IGN] signal BeiDou Résumé : (auteur) With the rapid deployment of the third-generation satellites of the BeiDou Navigation Satellite System (BDS-3), Wuhan University (WHU) has incorporated BDS-3 satellites to its routine Multi-GNSS analysis since Day of Year 1, 2019. This article summarizes the processing strategy and presents the validation results of the WHU BDS-3 orbit and clock solutions submitted to the International GNSS Service Multi-GNSS Experiment in 2019. Although more than 200 stations with B1I and B3I signals tracking capability can be used for BDS-3 precise orbit determination, the number of tracking stations for different satellites diverges greatly; in general, more stations track those launched early and less those deployed late. The validations with orbit boundary misclosures, orbit differences with respect to BDS-3 products of GeoForschungsZentrum (GFZ) and Satellite Laser Ranging (SLR) residuals show that the orbits are affected by the number of tracking stations and the deficiency of dynamic models. To overcome the latter, an a priori solar radiation pressure (SRP) model has been proposed considering the Earth albedo and antenna thrust. The SLR validation shows that the new SRP model significantly improves the orbit from 5 to 7 cm to about 3 to 4 cm by reducing the Sun-elongation-angle-dependent errors of the BDS-3 orbits. Besides, the clock products have been compared with those of GFZ, and the root-mean-square (RMS) of clock linear fit is also analyzed. Noticeable different quality has been shown for Rubidium Atomic Frequency Standard and Passive Hydrogen Maser (PHM) clocks. The Sun-elevation-angle-dependent patterns are identified in PHM clocks, and the RMS of clock linear fit of PHM clocks can be reduced with improved dynamic modeling, particularly in eclipse seasons. Numéro de notice : A2023-131 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01705-5 En ligne : https://doi.org/10.1007/s00190-023-01705-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102674 [article]

BDS and GPS side-lobe observation quality analysis and orbit determination with a GEO satellite onboard receiver / Wenwen Li in GPS solutions, vol 27 n° 1 (January 2023)  

Public [article]  inGPS solutions > vol 27 n° 1 (January 2023) . - n° 18 Titre : BDS and GPS side-lobe observation quality analysis and orbit determination with a GEO satellite onboard receiver Type de document : Article/Communication Auteurs : Wenwen Li, Auteur ; Kecai Jiang, Auteur ; Min Li, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 18 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] code GNSS [Termes IGN] orbite géostationnaire [Termes IGN] orbite précise [Termes IGN] orbitographie [Termes IGN] orbitographie par GNSS [Termes IGN] phase [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GPS Résumé : (auteur) Multi-GNSS combination can alleviate problems associated with GNSS-based geostationary earth orbit (GEO) satellite navigation and orbit determination (OD), such as GNSS availability and observation geometry deterioration. However, only GPS has been widely applied and investigated in GEO missions, whereas GEO OD with BDS requires further exploration. The Chinese GEO satellite TJS-5, equipped with a GPS and BDS-compatible receiver, is the first GEO mission that tracks both BDS 2nd and 3rd generation satellites since BDS global deployment. With the TJS-5 real onboard data, we evaluate BDS side-lobe signal performance and the BDS contribution to GEO OD. Due to transmit antenna gain deficiencies in the side lobes, BDS shows a worse tracking performance than GPS with an average satellite number of 4.3 versus 7.8. Both GPS and BDS reveal inconsistency between carrier-phase and code observations, which reaches several meters and significantly degrades post-dynamic OD calculation. We estimate the consistency as a random walk process in the carrier-phase observation model to reduce its impact. With inconsistency estimated, the post-fit carrier-phase residuals decrease from 0.21 to 0.09 m for both GPS and BDS. The OD precision is significantly improved, from 1.95 to 1.42 m with only GPS and from 3.14 to 2.71 m with only BDS; the GPS and BDS combined OD exhibits the largest improvement from 1.74 to 0.82 m, demonstrating that adding BDS improves the OD precision by 43.3%. The above results indicate that the proposed carrier-phase inconsistency estimation approach is effective for both GPS and BDS and can achieve an orbit precision within 1.0 m using multi-GNSS measurements. Numéro de notice : A2023-026 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01358-5 Date de publication en ligne : 06/11/2022 En ligne : https://doi.org/10.1007/s10291-022-01358-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102261 [article]

Field optical clocks and sensitivity to mass anomalies for geoscience applications / Guillaume Lion (2023)  

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Precise orbit determination for BDS-3 GEO satellites enhanced by intersatellite links / Xiaojie Li in GPS solutions, vol 27 n° 1 (January 2023)  

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Spatiotemporal accuracy evaluation and errors analysis of global VTEC maps using a simulation technique / Jian Lin in GPS solutions, vol 27 n° 1 (January 2023)  

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Modelling evacuation preparation time prior to floods: A machine learning approach / R. Sreejith in Sustainable Cities and Society, vol 87 (December 2022)  

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Precise onboard time synchronization for LEO satellites / Florian Kunzi in Navigation : journal of the Institute of navigation, vol 69 n° 3 (Fall 2022)  

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Le cheminement du douzième parallèle (deuxième partie) : article tiré de Jalon, bulletin de l’association des personnels retraités de l’IGN, n° 146-bis de mai 2022 / Jean-Claude Leblanc in XYZ, n° 172 (septembre 2022)

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Evaluation of QZSS orbit and clock products for real-time positioning applications / Brian Bramanto in Journal of applied geodesy, vol 16 n° 3 (July 2022)  

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A new ambiguity resolution method for LEO precise orbit determination / Xingyu Zhou in Journal of geodesy, vol 96 n° 7 (July 2022)  

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La puissance spatiale chinoise s’affirme / Laurent Polidori in Géomètre, n° 2203 (juin 2022)

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Adaptive Kalman filter for real-time precise orbit determination of low earth orbit satellites based on pseudorange and epoch-differenced carrier-phase measurements / Min Li in Remote sensing, vol 14 n° 9 (May-1 2022)  

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