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Estimation of antenna phase center offset for BDS IGSO and MEO satellites / Guanwen Huang in GPS solutions, vol 22 n° 2 (April 2018)  

Public [article]  inGPS solutions > vol 22 n° 2 (April 2018) . - pp 22 - 49 Titre : Estimation of antenna phase center offset for BDS IGSO and MEO satellites Type de document : Article/Communication Auteurs : Guanwen Huang, Auteur ; Xingyuan Yan, Auteur ; Zhang Qian, Auteur ; et al., Auteur Année de publication : 2018 Article en page(s) : pp 22 - 49 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] centre de phase [Termes IGN] constellation BeiDou [Termes IGN] orbite géostationnaire [Termes IGN] orbitographie Résumé : (Auteur) The BeiDou satellite navigation system (BDS) is different from other global navigation satellite systems (GNSSs) because of its special constellation, which consists of satellites in geostationary earth orbit, inclined geosynchronous earth orbit (IGSO), and medium earth orbit (MEO). Compared to MEO satellites, the observations of IGSO satellites cover only a small range of nadir angles. Therefore, the estimation of phase center offsets (PCOs) suffers from high correlation with other estimation parameters. We have estimated the phase center offsets for BeiDou IGSO and MEO satellites with a direct PCO parameters model, and constraints are applied to cope with the correlation between the PCOs and other parameters. Validation shows that the estimated PCO parameters could be used to improve the accuracy of orbit and clock offset overlaps. Compared with the Multi-GNSS Experiment antenna phase center correction model, the average improvements of the proposed method for along-track, cross-track, and radial components are 19 mm (31%), 5 mm (14%), and 2 mm (15%) for MEO satellites, and 13 mm (17%), 12 mm (21%), and 5 mm (19%) for IGSO satellites. For clock offset overlaps, average improvements of standard deviation and root mean square (RMS) are 0.03 ns (20%) and 0.03 ns (12%), respectively. The RMS of precise coordinates in the BDS-only positioning was also improved significantly with a level of 24 mm (30%) in the up-direction. Finally, the overall uncertainty of the estimated results is discussed. Numéro de notice : A2018-159 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-018-0716-z Date de publication en ligne : 24/02/2018 En ligne : https://doi.org/10.1007/s10291-018-0716-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89781 [article]

Multi-UAV surveillance over forested regions / Vengatesan Govindaraju in Photogrammetric Engineering & Remote Sensing, PERS, vol 80 n° 12 (December 2014)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 80 n° 12 (December 2014) . - pp 1129 - 1137 Titre : Multi-UAV surveillance over forested regions Type de document : Article/Communication Auteurs : Vengatesan Govindaraju, Auteur ; Gerard Leng, Auteur ; Zhang Qian, Auteur Année de publication : 2014 Article en page(s) : pp 1129 - 1137 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] couvert forestier [Termes IGN] diagramme de Voronoï [Termes IGN] drone [Termes IGN] point d'appui [Termes IGN] rayonnement incident [Termes IGN] relief [Termes IGN] simulation 3D [Termes IGN] tessellation Résumé : (auteur) S-UAVs (Small-Unmanned Aerial Vehicles) have emerged as low-cost alternatives for aerial surveillance over forests. However, they provide limited coverage owing to their low altitudes and short endurance. Therefore, a quick and effective surveillance necessitates optimal flying paths, maximizing ground visibility. Even though the occlusion of ground points due to vegetation is significant in forests, it is generally neglected. This paper proposes a probabilistic sensing model that incorporates both occlusions due to terrain and vegetation, in the visibility computations and presents a two-step approach to determine near-optimal flight paths: (a) waypoints are strategically deployed to enhance visibility, using centroidal Voronoi tessellation, and (b) flyable paths are designed using a clustered spiral-alternating algorithm. Simulation studies conducted on synthetic terrains and a reconstructed terrain, from satellite data of tree-cover and a Digital Elevation Model (DEM), show the effectiveness of the proposed method in improving the terrain visibility as compared to commonly used grid-based waypoints. Numéro de notice : A2014-669 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.14358/PERS.80.12.1129 En ligne : https://doi.org/10.14358/PERS.80.12.1129 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75128 [article]