Descripteur
Documents disponibles dans cette catégorie (1326)
Ajouter le résultat dans votre panier
Visionner les documents numériques
Affiner la recherche Interroger des sources externes
Etendre la recherche sur niveau(x) vers le bas
Characteristics of the BDS-3 multipath effect and mitigation methods using precise point positioning / Ran Lu in GPS solutions, vol 26 n° 2 (April 2022)
[article]
Titre : Characteristics of the BDS-3 multipath effect and mitigation methods using precise point positioning Type de document : Article/Communication Auteurs : Ran Lu, Auteur ; Wen Chen, Auteur ; Chenglong Zhang, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 41 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] constellation BeiDou
[Termes IGN] correction du trajet multiple
[Termes IGN] modèle stochastique
[Termes IGN] orbite géostationnaire
[Termes IGN] orbite terrestre
[Termes IGN] positionnement par BeiDou
[Termes IGN] positionnement ponctuel précis
[Termes IGN] répétabilité
[Termes IGN] trajet multipleRésumé : (auteur) Multipath effect is one of the main challenges of precise point positioning (PPP) in complex environments. Nowadays, the BeiDou global navigation satellite system (BDS-3) constellation was fully operational. We evaluated the multipath characteristics of BDS-3 open-service signals. The results indicate that the B2a signal had the best anti-multipath performance, and B1C signal had the worst capability. Since BDS-3 satellites with different orbital types have different orbital repeat time, the traditional method based on multipath time-domain repeatability is complicated to alleviate the multipath error on BDS-3 satellites. In contrast, the multipath spatial-domain repeatability method does not need to calculate the orbital repeat times and is only related to the position of the satellite in the sky. It has the advantages of simple algorithm and easy implementation. We selected a multipath hemispherical map (MHM) and a MHM based on trend-surface analysis (T-MHM) to evaluate the effects of BDS-3 PPP multipath correction. The positioning results for the inclined geosynchronous orbit (IGSO) and medium earth orbit (MEO) satellites, which were separately modeled and corrected, are slightly better than those obtained when they were modeled and corrected together. Compared with the uncorrected multipath, the positioning accuracy of B1I/B3I and B1C/B2a ionospheric-free (IF) combinations using the MHM can be improved by 52.7% and 51.6% and the convergence time can be shortened by 48.6% and 57.5%, respectively. The positioning accuracy of B1I/B3I and B1C/B2a IF combinations using the T-MHM can be improved by 67% and 66.9% and the convergence time can be shortened by 69.3% and 76.5%, respectively. The T-MHM introduces trend-surface analysis to model the spatial variation of the multipath inside the grid, which effectively alleviates high-frequency and low-frequency multipath. This study is of great significance for further improvements to the application of BDS-3 in complex environments. Numéro de notice : A2022-106 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-022-01227-1 Date de publication en ligne : 24/01/2022 En ligne : https://doi.org/10.1007/s10291-022-01227-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99606
in GPS solutions > vol 26 n° 2 (April 2022) . - n° 41[article]Effect of PCV and attitude on the precise orbit determination of Jason-3 satellite / Kai Li in Journal of applied geodesy, vol 16 n° 2 (April 2022)
[article]
Titre : Effect of PCV and attitude on the precise orbit determination of Jason-3 satellite Type de document : Article/Communication Auteurs : Kai Li, Auteur ; Xuhua Zhou, Auteur ; Nannan Guo, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : pp 143 - 150 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales
[Termes IGN] capteur d'orientation
[Termes IGN] centre de phase
[Termes IGN] données Jason
[Termes IGN] orbite basse
[Termes IGN] orbitographie
[Termes IGN] perturbation orbitaleRésumé : (auteur) Satellite attitude modes and antenna phase center variations have a great influence on the Precise Orbit Determination (POD) of Low Earth Orbit satellites (LEOs). Inaccurate information about spacecraft attitude, phase center offsets and variations in the POD leads to orbital error. The Jason-3 satellite experienced complex attitude modes which are fixed, sinusoidal, ramp-up/down and yaw-flip. Therefore, it is necessary to properly construct the attitude model in the process of POD especially when there is no external attitude data. For the antenna phase center correction, the PCO which is the deviation between Antenna Reference Point (ARP) and Mean Antenna Phase Center (MAPC) usually can be calibrated on the ground accurately, but the PCV which is the deviation between Instantaneous Antenna Phase Center (IAPC) and Mean Antenna Phase Center (MAPC) will change greatly with the change of space environment. Residual approach can be used to estimate the receiver PCV map. In this paper, we collected the on-board GPS data of Jason-3 satellite from January 2019 and analyzed the impacts of PCV and spacecraft attitude on the orbit accuracy by performing the reduced-dynamic POD. Compared with the reference orbit released by the Centre National d’Études Spatiales (CNES), using the PCV map can reduce the Root Mean Square (RMS) of orbit differences in the Radial (R), Along-track (T), Cross-track (N) and 3D direction about 0.3, 1.0, 0.9, and 1.4 mm. Based on the estimated PCV map, the orbit accuracy in R, T, N and 3D direction is 1.24, 2.81, 1.17, and 3.29 cm respectively by using the measured attitude data. When using the attitude model, the orbit accuracy in R, T, N and 3D directions is 1.60, 3.54, 1.33, and 4.13 cm, respectively. The results showed that the combination of measured attitude data and modeled PCV map can obtain the better orbit solution. It is essential to build a corresponding model in high-precision orbit determination, when there is no attitude data and PCV map. Numéro de notice : A2022-251 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2021-0052 Date de publication en ligne : 26/01/2022 En ligne : https://doi.org/10.1515/jag-2021-0052 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100204
in Journal of applied geodesy > vol 16 n° 2 (April 2022) . - pp 143 - 150[article]LEO satellite clock analysis and prediction for positioning applications / Kan Wang in Geo-spatial Information Science, vol 25 n° 1 (March 2022)
[article]
Titre : LEO satellite clock analysis and prediction for positioning applications Type de document : Article/Communication Auteurs : Kan Wang, Auteur ; Ahmed El-Mowafy, Auteur Année de publication : 2022 Article en page(s) : pp 14 - 33 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] chronométrie
[Termes IGN] horloge du satellite
[Termes IGN] orbite basse
[Termes IGN] oscillateur
[Termes IGN] relativité généraleRésumé : (auteur) The positioning service aided by low Earth orbit (LEO) mega-constellations has become a hot topic in recent years. To achieve precise positioning, accuracy of the LEO clocks is important for single-receiver users. To bridge the gap between the applicable time of the clock products and the time of positioning, the precise LEO clocks need to be predicted over a certain period depending on the sampling interval of the clock products. This study discusses the prediction errors for periods from 10 s to 1 h for two typical LEO clock types, i.e. the ultra-stable oscillator (USO) and the oven-controlled crystal oscillator (OCXO). The prediction is based on GNSS-determined precise clock estimates, where the clock stability is related to the GNSS estimation errors, the behaviors of the oscillators themselves, the systematic effects related to the environment and the relativistic effects, and the stability of the time reference. Based on real data analysis, LEO clocks of the two different types are simulated under different conditions, and a prediction model considering the systematic effects is proposed. Compared to a simple polynomial fitting model usually applied, the proposed model can significantly reduce the prediction errors, i.e. by about 40%-70% in simulations and about 5%-30% for real data containing different miss-modeled effects. For both clock types, short-term prediction of 1 min would result in a root mean square error (RMSE) of a few centimeters when using a very stable time reference. The RMSE amounts to about 0.1 m, when a typical real-time time reference of the national center for space studies (CNES) real-time clocks was used. For long-term prediction of 1 h, the RMSE could range from below 1 m to a few meters for the USOs, depending on the complexity of the miss-modeled effects. For OCXOs, the 1 h prediction could lead to larger errors with an RMSE of about 10 m. Numéro de notice : A2022-303 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/10095020.2021.1917310 Date de publication en ligne : 08/06/2021 En ligne : https://doi.org/10.1080/10095020.2021.1917310 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100377
in Geo-spatial Information Science > vol 25 n° 1 (March 2022) . - pp 14 - 33[article]The number of tree species on Earth / Roberto Cazzolla Gatti in Proceedings of the National Academy of Sciences of the United States of America PNAS, vol 119 n° 6 (2022)
[article]
Titre : The number of tree species on Earth Type de document : Article/Communication Auteurs : Roberto Cazzolla Gatti, Auteur ; Peter B. Reich, Auteur ; Javier G. P. Gamarra, Auteur ; et al., Auteur ; Olivier Bouriaud , Auteur Année de publication : 2022 Article en page(s) : n° e2115329119 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] distribution spatiale
[Termes IGN] essence d'arbre
[Termes IGN] forêt
[Termes IGN] richesse floristique
[Termes IGN] Terre (planète)
[Vedettes matières IGN] Ecologie forestièreRésumé : (auteur) One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness. Numéro de notice : A2022-155 Affiliation des auteurs : non IGN Thématique : BIODIVERSITE/FORET Nature : Article DOI : 10.1073/pnas.2115329119 Date de publication en ligne : 31/01/2022 En ligne : https://doi.org/10.1073/pnas.2115329119 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100309
in Proceedings of the National Academy of Sciences of the United States of America PNAS > vol 119 n° 6 (2022) . - n° e2115329119[article]Calibrating GNSS phase biases with onboard observations of low earth orbit satellites / Xingxing Li in Journal of geodesy, vol 96 n° 2 (February 2022)
[article]
Titre : Calibrating GNSS phase biases with onboard observations of low earth orbit satellites Type de document : Article/Communication Auteurs : Xingxing Li, Auteur ; Jiaqi Wu, Auteur ; Xin Li, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 8 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] bande K
[Termes IGN] erreur de phase
[Termes IGN] erreur systématique
[Termes IGN] étalonnage des données
[Termes IGN] orbite basse
[Termes IGN] phase GNSS
[Termes IGN] positionnement ponctuel précis
[Termes IGN] résolution d'ambiguïtéRésumé : (auteur) recent years, numerous low earth orbit (LEO) satellites have been launched for different scientific tasks such as the Earth’s magnetic field, gravity recovering and ocean altimetry. The LEO satellites can cover the ocean area and are less affected by atmospheric delays and multipath errors, which provides new opportunities for calibrating the phase biases of the Global Navigation Satellite System (GNSS). In this contribution, we propose an alternative approach for uncalibrated phase delay (UPD) estimation by making full use of onboard observations of LEO satellites. Stable wide-lane (WL) and narrow-lane (NL) UPDs can be obtained from spaceborne GNSS observations and agree well with the UPD products derived from 106 IGS stations. To further verify the feasibility of the proposed method for UPD estimation, zero-difference (ZD) ambiguity resolution (AR) for precise point positioning (PPP) and LEO precise orbit determination (POD) are implemented. After applying the LEO-based UPDs, the averaged convergence time for PPP AR can be reduced to 15.2 min, with an improvement of 24% compared to float solutions. As for LEO AR, the fixing rates of WL and NL ambiguities exceed 98 and 92%, respectively. The accuracies of ambiguity-fixed orbits are validated by comparing with external satellite laser ranging (SLR) and K-band ranging (KBR) observations. Compared to float solutions, the standard deviations (STDs) of SLR residuals can be reduced by 8 ~ 43%, and the KBR residuals of 3.75 mm can be achieved for fixed solutions using LEO-based UPDs, with an improvement of 60%. Although the current UPD results derived from LEO satellites are slightly worse than those of ground-based UPD, it is anticipated that the performance of LEO-based UPD can be further improved in the near future with the rapidly increasing number of LEO satellites and the continuous refinements of the POD method. Numéro de notice : A2022-129 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s00190-022-01600-5 Date de publication en ligne : 31/01/2022 En ligne : https://doi.org/10.1007/s00190-022-01600-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99712
in Journal of geodesy > vol 96 n° 2 (February 2022) . - n° 8[article]Comparison of atmospheric mass density models using a new data source: COSMIC satellite ephemerides / Yang Yang in IEEE Aerospace and Electronic Systems Magazine, vol 37 n° 2 (February 2022)PermalinkDébris spatiaux, l’inquiétante prolifération / Laurent Polidori in Géomètre, n° 2199 (février 2022)PermalinkMLMT-CNN for object detection and segmentation in multi-layer and multi-spectral images / Majedaldein Almahasneh in Machine Vision and Applications, vol 33 n° 1 (January 2022)PermalinkOn-orbit BDS signals and transmit antenna gain analysis for a geostationary satellite / Meng Wang in Advances in space research, vol 69 n° 7 (April 2022)PermalinkPermalinkBroadcast ephemerides for LEO augmentation satellites based on nonsingular elements / Lingdong Meng in GPS solutions, vol 25 n° 4 (October 2021)PermalinkLes journées de la Recherche IGN 2021 / Anonyme in Géomatique expert, n° 135 (septembre 2021)PermalinkGPS satellite differential code bias estimation with current eleven low earth orbit satellites / Xingxing Li in Journal of geodesy, vol 95 n° 7 (July 2021)PermalinkGravitational field modelling near irregularly shaped bodies using spherical harmonics: a case study for the asteroid (101955) Bennu / Blažej Bucha in Journal of geodesy, vol 95 n° 5 (May 2021)PermalinkPléiades Neo, 4 satellites réactifs / Laurent Polidori in Géomètre, n° 2191 (mai 2021)Permalink