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Self-shadowing of a spacecraft in the computation of surface forces : An example in planetary geodesy / Georges Balmino in Artificial satellites, vol 53 n° 1 (March 2018)
[article]
Titre : Self-shadowing of a spacecraft in the computation of surface forces : An example in planetary geodesy Type de document : Article/Communication Auteurs : Georges Balmino, Auteur ; J.C. Marty, Auteur Année de publication : 2018 Article en page(s) : pp 1 - 27 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales
[Termes IGN] décomposition
[Termes IGN] détection d'ombre
[Termes IGN] engin spatial
[Termes IGN] Mars (planète)
[Termes IGN] problème inverse
[Termes IGN] surface (géométrie)Résumé : (auteur) We describe in details the algorithms used in modelling the self-shadowing between spacecraft components, which appears when computing the surface forces as precisely as possible and especially when moving parts are involved. This becomes necessary in planetary geodesy inverse problems using more and more precise orbital information to derive fundamental parameters of geophysical interest. Examples are given with two Mars orbiters, which show significant improvement on drag and solar radiation pressure model multiplying factors, a prerequisite for improving in turn the determination of other global models. Numéro de notice : A2018-173 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.2478/arsa-2018-0002 Date de publication en ligne : 24/03/2018 En ligne : https://doi.org/10.2478/arsa-2018-0002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89813
in Artificial satellites > vol 53 n° 1 (March 2018) . - pp 1 - 27[article]3D visualization of trees based on a sphere-board model / Jiangfeng She in ISPRS International journal of geo-information, vol 7 n° 2 (February 2018)
[article]
Titre : 3D visualization of trees based on a sphere-board model Type de document : Article/Communication Auteurs : Jiangfeng She, Auteur ; Xingchen Guo, Auteur ; Xin Tan, Auteur ; Jianlong Liu, Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] arbre (flore)
[Termes IGN] modèle de croissance végétale
[Termes IGN] rendu réaliste
[Termes IGN] sphère
[Termes IGN] visualisation 3D
[Vedettes matières IGN] ForesterieRésumé : (Auteur) Because of the smooth interaction of tree systems, the billboard and crossed-plane techniques of image-based rendering (IBR) have been used for tree visualization for many years. However, both the billboard-based tree model (BBTM) and the crossed-plane tree model (CPTM) have several notable limitations; for example, they give an impression of slicing when viewed from the top side, and they produce an unimpressive stereoscopic effect and insufficient lighted effects. In this study, a sphere-board-based tree model (SBTM) is proposed to eliminate these defects and to improve the final visual effects. Compared with the BBTM or CPTM, the proposed SBTM uses one or more sphere-like 3D geometric surfaces covered with a virtual texture, which can present more details about the foliage than can 2D planes, to represent the 3D outline of a tree crown. However, the profile edge presented by a continuous surface is overly smooth and regular, and when used to delineate the outline of a tree crown, it makes the tree appear very unrealistic. To overcome this shortcoming and achieve a more natural final visual effect of the tree model, an additional process is applied to the edge of the surface profile. In addition, the SBTM can better support lighted effects because of its cubic geometrical features. Interactive visualization effects for a single tree and a grove are presented in a case study of Sabina chinensis. The results show that the SBTM can achieve a better compromise between realism and performance than can the BBTM or CPTM. Numéro de notice : A2018-106 Affiliation des auteurs : non IGN Thématique : FORET/GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.3390/ijgi7020039 En ligne : https://doi.org/10.3390/ijgi7020045 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89532
in ISPRS International journal of geo-information > vol 7 n° 2 (February 2018)[article]Partial polygon pruning of hydrographic features in automated generalization / Alexander K. Stum in Transactions in GIS, vol 21 n° 5 (October 2017)
[article]
Titre : Partial polygon pruning of hydrographic features in automated generalization Type de document : Article/Communication Auteurs : Alexander K. Stum, Auteur ; Barbara P. Buttenfield, Auteur ; Lauwrence V. Stanislawski, Auteur Année de publication : 2017 Article en page(s) : pp 1061–1078 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] base de données hydrographiques
[Termes IGN] détection automatique
[Termes IGN] Etats-Unis
[Termes IGN] généralisation automatique de données
[Termes IGN] petite échelle
[Termes IGN] polygone
[Termes IGN] rendu (géovisualisation)
[Termes IGN] simplification de contour
[Termes IGN] traitement automatique de données
[Vedettes matières IGN] GénéralisationRésumé : (Auteur) This article demonstrates a working method to automatically detect and prune portions of waterbody polygons to support creation of a multi-scale hydrographic database. Water features are sensitive to scale change, therefore multiple representations are required to maintain visual and geographic logic at smaller scales. Partial pruning of polygonal features – such as long, sinuous reservoir arms, stream channels too narrow at the target scale, and islands that begin to coalesce – entails concurrent management of the length and width of polygonal features as well as integrating pruned polygons with other generalized point and linear hydrographic features to maintain stream network connectivity. The implementation follows data representation standards developed by the US Geological Survey (USGS) for the National Hydrography Dataset (NHD). Portions of polygonal rivers, streams, and canals are automatically characterized for width, length, and connectivity. This article describes an algorithm for automatic detection and subsequent processing, and shows results for a sample of NHD subbasins in different landscape conditions in the US. Numéro de notice : A2017-634 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/tgis.12270 En ligne : http://dx.doi.org/10.1111/tgis.12270 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86953
in Transactions in GIS > vol 21 n° 5 (October 2017) . - pp 1061–1078[article]A parallel scheme for large-scale polygon rasterization on CUDA-enabled GPUs / Chen Zhou in Transactions in GIS, vol 21 n° 3 (June 2017)
[article]
Titre : A parallel scheme for large-scale polygon rasterization on CUDA-enabled GPUs Type de document : Article/Communication Auteurs : Chen Zhou, Auteur ; Zhenjie Chen, Auteur ; Yuzhe Pian, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 608 – 631 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique
[Termes IGN] données massives
[Termes IGN] maillage
[Termes IGN] polygone
[Termes IGN] processeur
[Termes IGN] processeur graphique
[Termes IGN] rastérisation
[Termes IGN] temps
[Termes IGN] traitement parallèleRésumé : (Auteur) This research develops a parallel scheme to adopt multiple graphics processing units (GPUs) to accelerate large-scale polygon rasterization. Three new parallel strategies are proposed. First, a decomposition strategy considering the calculation complexity of polygons and limited GPU memory is developed to achieve balanced workloads among multiple GPUs. Second, a parallel CPU/GPU scheduling strategy is proposed to conceal the data read/write times. The CPU is engaged with data reads/writes while the GPU rasterizes the polygons in parallel. This strategy can save considerable time spent in reading and writing, further improving the parallel efficiency. Third, a strategy for utilizing the GPU's internal memory and cache is proposed to reduce the time required to access the data. The parallel boundary algebra filling (BAF) algorithm is implemented using the programming models of compute unified device architecture (CUDA), message passing interface (MPI), and open multi-processing (OpenMP). Experimental results confirm that the implemented parallel algorithm delivers apparent acceleration when a massive dataset is addressed (50.32 GB with approximately 1.3 × 108 polygons), reducing conversion time from 25.43 to 0.69 h, and obtaining a speedup ratio of 36.91. The proposed parallel strategies outperform the conventional method and can be effectively extended to a CPU-based environment. Numéro de notice : A2017-626 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/tgis.12213 En ligne : http://dx.doi.org/10.1111/tgis.12213 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86941
in Transactions in GIS > vol 21 n° 3 (June 2017) . - pp 608 – 631[article]A spatial zoning approach to calibrate and validate urban growth models / Ali Kazemzadeh-Zow in International journal of geographical information science IJGIS, vol 31 n° 3-4 (March-April 2017)
[article]
Titre : A spatial zoning approach to calibrate and validate urban growth models Type de document : Article/Communication Auteurs : Ali Kazemzadeh-Zow, Auteur ; Saeed Zanganeh Shahraki, Auteur ; Luca Salvati, Auteur ; Najmeh Neisani Samani, Auteur Année de publication : 2017 Article en page(s) : pp 763 - 782 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale
[Termes IGN] modèle de simulation
[Termes IGN] polygone de Thiessen
[Termes IGN] surveillance de l'urbanisation
[Termes IGN] urbanisation
[Termes IGN] utilisation du solRésumé : (Auteur) Calibration and validation of models predicting urban growth have been largely developed using internal variables. Further investigation is required to improve model’s calibration and validation mixing internal and external variables. To reach this objective, a spatial zoning approach simulating long-term expansion of Mashhad, the second largest city of Iran, was presented in this study. Spatial zoning approaches distinguish local-scale urban dynamics in districts with different socioeconomic characteristics. Thiessen polygons were used to identify districts with different morphology and functional attributes. Urban growth was subsequently simulated for each district using a Multi-Layer Perceptron (MLP) neural network and Markov chains (MC) analysis. MLP and MC algorithms were respectively used to derive transition maps from non-urban to urban use of land and to determine spatial evolution of built-up areas at the metropolitan scale. Results of simulations based on spatial zoning were compared with outcomes of traditional urban growth models. Spatial zoning improved significantly model’s accuracy in respect to more traditional simulation modes. The approach proposed here is appropriate when simulating land-use changes under discontinuous urban expansion. Numéro de notice : A2017-082 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/URBANISME Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2016.1236927 En ligne : http://dx.doi.org/10.1080/13658816.2016.1236927 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84345
in International journal of geographical information science IJGIS > vol 31 n° 3-4 (March-April 2017) . - pp 763 - 782[article]Réservation
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