Descripteur
Documents disponibles dans cette catégorie (66)
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
Benefits of satellite clock modeling in BDS and Galileo orbit determination / Yun Qing in Advances in space research, vol 60 n° 12 (15 December 2017)
[article]
Titre : Benefits of satellite clock modeling in BDS and Galileo orbit determination Type de document : Article/Communication Auteurs : Yun Qing, Auteur ; Yidong Lou, Auteur ; Xiaolei Dai, Auteur ; Yang Liu, Auteur Année de publication : 2017 Article en page(s) : pp 2550 - 2560 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales
[Termes IGN] constellation BeiDou
[Termes IGN] constellation Galileo
[Termes IGN] horloge atomique
[Termes IGN] modèle numérique
[Termes IGN] orbitographie
[Termes IGN] résiduRésumé : (auteur) In the process of Global Navigation Satellite Systems (GNSS) satellite orbit determination, satellite clocks are typically estimated as epoch-wise white noise in addition to the satellite orbit parameters. This results in high correlation between the satellite clock estimates and the satellite orbits, especially the radial component. In this paper, an appropriate clock model is proposed to constrain the satellite clock estimates in order to improve the accuracy of satellite orbits. SLR residuals and Day Boundary Discontinuities (DBDs) were used to assess the orbit quality. The benefits of satellite clock modeling in BDS and Galileo orbit determination is validated by experimental data sets. The results show that for satellites equipped with highly stable clocks, employing an appropriate linear model constraint for the clock estimates in orbit determination can result in an improved orbit consistency as well as accuracy. In detail, for Medium Earth Orbit (MEO) satellites, C12, C14, E11, E12 and E19, the improvements of DBDs range from 10% to 20%. Furthermore, the Standard Deviation (STD) of Satellite Laser Ranging (SLR) residuals were improved up to 30% for the Galileo satellites (using a passive hydrogen maser clock). Numéro de notice : A2017-753 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2017.03.040 Date de publication en ligne : 04/04/2017 En ligne : https://doi.org/10.1016/j.asr.2017.03.040 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89038
in Advances in space research > vol 60 n° 12 (15 December 2017) . - pp 2550 - 2560[article]An analysis of movement patterns between zones using taxi GPS data / Zhanlong Chen in Transactions in GIS, vol 21 n° 6 (December 2017)
[article]
Titre : An analysis of movement patterns between zones using taxi GPS data Type de document : Article/Communication Auteurs : Zhanlong Chen, Auteur ; Xi Gong, Auteur ; Zhong Xie, Auteur Année de publication : 2017 Article en page(s) : pp 1341 - 1363 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] modèle numérique
[Termes IGN] Pékin (Chine)
[Termes IGN] trace GPS
[Termes IGN] trajectographie par GPS
[Termes IGN] trajet (mobilité)
[Termes IGN] urbanisme
[Termes IGN] véhicule automobile
[Vedettes matières IGN] GéovisualisationRésumé : (auteur) The discovery of zones and people's movement patterns supports a better understanding of modern cities and enables a more comprehensive strategy for urban planning. This article proposes a modified method based on previous research to simultaneously discover people's zones and movement patterns, called movement patterns between functional zones (MPFZ). The method attempts to take full advantage of taxi GPS data to identify MPFZs by merging the movement traces satisfying the merging conditions. Considering movement directions, movement numbers and the adjacent constraints that consist of spatial relationship and attribute features, the merging conditions limit the movement traces to be merged. The new MPFZs are discovered by an iteration process and are measured by the following three evaluation indices: v‐value, a‐value and c‐value, which represent coverage, accuracy and their trade‐off. Using a real‐world taxi dataset of Beijing, 24 new MPFZs are discovered, which have higher v‐, a‐ and c‐values than the unmerged MPFZs. The results of the real‐world dataset experiment show that the proposed approach is effective and efficient. The proposed method can also be applied to other types of transportation data and regions by adjusting the dataset utilized and controlling the iteration process. Numéro de notice : A2017-839 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/tgis.12281 Date de publication en ligne : 07/08/2017 En ligne : https://doi.org/10.1111/tgis.12281 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89375
in Transactions in GIS > vol 21 n° 6 (December 2017) . - pp 1341 - 1363[article]Wind loads and competition for light sculpt trees into self-similar structures / Christophe Eloy in Nature communications, vol 8 (2017)
[article]
Titre : Wind loads and competition for light sculpt trees into self-similar structures Type de document : Article/Communication Auteurs : Christophe Eloy, Auteur ; Meriem Fournier, Auteur ; André Lacointe, Auteur ; Bruno Moulia, Auteur Année de publication : 2017 Langues : Anglais (eng) Descripteur : [Termes IGN] arbre (flore)
[Termes IGN] croissance des arbres
[Termes IGN] données allométriques
[Termes IGN] modèle numérique
[Termes IGN] rayonnement lumineux
[Termes IGN] structure de la végétation
[Termes IGN] vent
[Vedettes matières IGN] BotaniqueRésumé : (auteur) Trees are self-similar structures: their branch lengths and diameters vary allometrically within the tree architecture, with longer and thicker branches near the ground. These tree allometries are often attributed to optimisation of hydraulic sap transport and safety against elastic buckling. Here, we show that these allometries also emerge from a model that includes competition for light, wind biomechanics and no hydraulics. We have developed MECHATREE, a numerical model of trees growing and evolving on a virtual island. With this model, we identify the fittest growth strategy when trees compete for light and allocate their photosynthates to grow seeds, create new branches or reinforce existing ones in response to wind-induced loads. Strikingly, we find that selected trees species are self-similar and follow allometric scalings similar to those observed on dicots and conifers. This result suggests that resistance to wind and competition for light play an essential role in determining tree allometries. Numéro de notice : A2017-780 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1038/s41467-017-00995-6 En ligne : https://doi.org/10.1038/s41467-017-00995-6 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=88980
in Nature communications > vol 8 (2017)[article]Geospatial analysis as experimental archaeology / Thomas G. Whitley in Journal of archaeological science, vol 84 (August 2017)
[article]
Titre : Geospatial analysis as experimental archaeology Type de document : Article/Communication Auteurs : Thomas G. Whitley, Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale
[Termes IGN] archéologie
[Termes IGN] dynamique spatiale
[Termes IGN] géovisualisation
[Termes IGN] modèle numérique
[Termes IGN] système d'information géographique
[Termes IGN] visualisation de donnéesRésumé : (auteur) In the more than 25 years since Allen et al. (1990), GIS and other kinds of geospatial analysis have become tools used almost as ubiquitously in archaeology as the trowel and the total station. However, can we consider it a “paradigm-shifter?” One fundamental distinction between archaeology and other scientific pursuits is the lack of a formal experimental procedure for testing large-scale hypotheses. We can experiment with some material culture methods or archaeological ‘models’ on a 1:1 analogue scale, but we rarely examine ideas about larger mechanisms; particularly those that encompass wide geographic areas in a formal experimental way. Geospatial technologies give us new tools and abilities to recognize patterns in archaeological sites and landscapes. Nevertheless, have they truly changed the way we make the transition from material remains to interpreting human behavior? We tend to present geospatial research that is either descriptive or methodological in nature rather than interpretive or explanatory. What is missing is the recognition that the ‘patterns’ we can see are an incomplete and abstract product of past human agency or behavior that cannot be worked backwards from, but must be envisioned as mechanisms in action. Within a mechanistic framework, we can experiment with archaeological research questions in much greater depth and detail, in a manner more akin to psychology than the ‘harder’ sciences. Although these techniques bring with them some theoretical assumptions and methodological challenges, their outcomes can provide logical and convincing visualizations of dynamic phenomena in enlightening ways. Presented here are several brief examples. Numéro de notice : A2017-199 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1016/j.jas.2017.05.008 En ligne : https://doi.org/10.1016/j.jas.2017.05.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84925
in Journal of archaeological science > vol 84 (August 2017)[article]Coverage of high biomass forests by the ESA BIOMASS mission under defense restrictions / João M.B. Carreiras in Remote sensing of environment, vol 196 (July 2017)
[article]
Titre : Coverage of high biomass forests by the ESA BIOMASS mission under defense restrictions Type de document : Article/Communication Auteurs : João M.B. Carreiras, Auteur ; Shaun Quegan, Auteur ; Thuy Le Toan, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 154 - 162 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] bande P
[Termes IGN] Biomass
[Termes IGN] biomasse aérienne
[Termes IGN] couvert forestier
[Termes IGN] image radar moirée
[Termes IGN] modèle numérique
[Termes IGN] puits de carbone
[Vedettes matières IGN] Végétation et changement climatiqueRésumé : (auteur) The magnitude of the global terrestrial carbon pool and related fluxes to and from the atmosphere are still poorly known. The European Space Agency P-band radar BIOMASS mission will help to reduce this uncertainty by providing unprecedented information on the distribution of forest above-ground biomass (AGB), particularly in the tropics where the gaps are greatest and knowledge is most needed. Mission selection was made in full knowledge of coverage restrictions over Europe, North and Central America imposed by the US Department of Defense Space Objects Tracking Radar (SOTR) stations. Under these restrictions, only 3% of AGB carbon stock coverage is lost in the tropical forest biome, with this biome representing 66% of global AGB carbon stocks in 2005. The loss is more significant in the temperate (72%), boreal (37%) and subtropical (29%) biomes, with these accounting for approximately 12%, 15% and 7%, respectively, of the global forest AGB carbon stocks. In terms of global carbon cycle modelling, there is minimal impact in areas of high AGB density, since mainly lower biomass forests in cooler climates are affected. In addition, most areas affected by the SOTR stations are located in industrialized countries with well-developed national forest inventories, so that extensive information on AGB is already available. Hence the main scientific objectives of the BIOMASS mission are not seriously compromised. Furthermore, several space sensors that can estimate AGB in lower biomass forests are in orbit or planned for launch between now and the launch of BIOMASS in 2021, which will help to fill the gaps in mission coverage. Numéro de notice : A2017-808 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2017.05.003 En ligne : https://doi.org/10.1016/j.rse.2017.05.003 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89247
in Remote sensing of environment > vol 196 (July 2017) . - pp 154 - 162[article]Augmented reality as a digital teaching environment to develop spatial thinking / Carlos Carbonell-Carrera in Cartography and Geographic Information Science, Vol 44 n° 3 (May 2017)PermalinkPotential of satellite-derived ecosystem functional attributes to anticipate species range shifts / Domingo Alcaraz-Segura in International journal of applied Earth observation and geoinformation, vol 57 (May 2017)PermalinkPathways to bridge the biophysical realism gap in ecosystem services mapping approaches / Sandra Lavorel in Ecological indicators, vol 74 (March 2017)PermalinkFrom inventory to consumer biomass availability - the ITOC model / Udo Mantau in Annals of Forest Science, vol 73 n° 4 (December 2016)PermalinkLinking ecosystem services with state-and-transition models to evaluate rangeland management decisions / Sapana Lohani in Global ecology and conservation, vol 8 (October 2016)PermalinkUrban soundscape maps modelled with geo-referenced data / Catherine Lavandier in Noise mapping, vol 3 n° 1 (October 2016)PermalinkQuantitative assessment of meteorological and tropospheric Zenith Hydrostatic Delay models / Di Zhang in Advances in space research, vol 58 n° 6 (September 2016)PermalinkSlicing method for curved façade and window extraction from point clouds / S.M. Iman Zolanvari in ISPRS Journal of photogrammetry and remote sensing, vol 119 (September 2016)PermalinkThe impact of land use/land cover scale on modelling urban ecosystem services / Darren R. Grafius in Landscape ecology, vol 31 n° 7 (September 2016)PermalinkAllometric models for estimating tree volume and aboveground biomass in lowland forests of Tanzania / Wilson Ancelm Mugasha in International journal of forestry research, vol 2016 ([01/08/2016])Permalink