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Monitoring elevation variations in leaf phenology of deciduous broadleaf forests from SPOT/VEGETATION time-series / Dominique Guyon in Remote sensing of environment, vol 115 n° 2 ([15/02/2011])
[article]
Titre : Monitoring elevation variations in leaf phenology of deciduous broadleaf forests from SPOT/VEGETATION time-series Type de document : Article/Communication Auteurs : Dominique Guyon, Auteur ; Marie Guillot, Auteur ; Yann Vitasse, Auteur ; et al., Auteur Année de publication : 2011 Article en page(s) : pp 615 - 627 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation
[Termes IGN] analyse des mélanges temporels
[Termes IGN] analyse diachronique
[Termes IGN] Fagus (genre)
[Termes IGN] feuillu
[Termes IGN] image SPOT-Végétation
[Termes IGN] indice de végétation
[Termes IGN] phénologie
[Termes IGN] Pyrénées (montagne)
[Termes IGN] Quercus (genre)
[Termes IGN] variation saisonnièreMots-clés libres : Phenology Leaf unfolding Deciduous forest Elevation VEGETATION Perpendicular vegetation index temporal unmixing Résumé : (auteur) In mountain forest ecosystems where elevation gradients are prominent, temperature gradient-based phenological variability can be high. However, there are few studies that assess the capability of remote sensing observations to monitor ecosystem phenology along elevation gradients, despite their relevance under climate change. We investigated the potential of medium resolution remotely sensed data to monitor the elevation variations in the seasonal dynamics of a temperate deciduous broadleaf forested ecosystem. Further, we explored the impact of elevation on the onset of spring leafing. This study was based on the analysis of multi-annual time-series of VEGETATION data acquired over the French Pyrenees Mountain Region (FPMR), in conjunction with simultaneous ground-based observations of leaf phenology made for two dominant tree species in the region (oak and beech). The seasonal variations in the perpendicular vegetation index (PVI) were analyzed during a five-year period (2002 to 2006). The five years of data were averaged into a one sole year in order to fill the numerous large spatio-temporal gaps due to cloud and snow presence – frequent in mountains – without altering the temporal resolution. Since a VEGETATION pixel (1 km²) includes several types of land cover, the broadleaf forest-specific seasonal dynamics of PVI was reconstructed pixel-by-pixel using a temporal unmixing method based on a non-parametric statistical approach. The spatial pattern of the seasonal response of PVI was clearly consistent with the relief. Nevertheless the elevational or geographic range of tree species, which differ in their phenology sensitivity to temperature, also has a significant impact on this pattern. The reduction in the growing season length with elevation was clearly observable from the delay in the increase of PVI in spring and from the advance of its decrease in the fall. The elevation variations in leaf flushing timing were estimated from the temporal change in PVI in spring over the study area. They were found to be consistent with those measured in situ (R2 > 0.95). It was deduced that, over FPMR, the mean delay of leaf flushing timing for every 100 m increase in elevation was estimated be approximately 2.3 days. The expected estimation error of satellite-based leaf unfolding date for a given elevation was approximately 2 days. This accuracy can be considered as satisfactory since it would allow us to detect changes in leafing timing of deciduous broadleaf forests with a magnitude equivalent to that due to an elevation variation of 100 m (2.3 days on average), or in other words, to that caused by a variation in the mean annual air temperature of 0.5 °C. Although averaging the VEGETATION data over five years led to a loss of interannual information, it was found to be a robust approach to characterise the elevation variations in spring leafing and its long-term trends. Numéro de notice : A2011-563 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2010.10.006 En ligne : https://doi.org/10.1016/j.rse.2010.10.006 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74834
in Remote sensing of environment > vol 115 n° 2 [15/02/2011] . - pp 615 - 627[article]Analysing landmarks in nature and elements of geospatial images to support wayfinding / Pyry Kettunen (2014)
Titre : Analysing landmarks in nature and elements of geospatial images to support wayfinding Type de document : Thèse/HDR Auteurs : Pyry Kettunen, Auteur Editeur : Helsinki : Finnish Geodetic Institute FGI Année de publication : 2014 Collection : Publications of the Finnish Geodetic Institute, ISSN 0085-6932 num. 155 Importance : 150 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-951-711-312-0 Note générale : bibliographie
Doctoral dissertation for the degree of Doctor of Science in Technology (Doctor of Philosophy) to be presented with due permission of the School of Engineering for public examination and debate in Auditorium M1 at the Aalto University School of Engineering (Espoo, Finland) on the 4th of October 2014 at 12 noon.Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] carte en 3D
[Termes IGN] croquis topographique
[Termes IGN] oculométrie
[Termes IGN] point de repère
[Termes IGN] signalisation routièreMots-clés libres : landmark wayfinding spatial knowledge perception recall route nature geospatial image 3D map elevation eye tracking Résumé : (auteur) This dissertation applies the research and methods of spatial cognition in order to contribute to the development of wayfinding support in geospatial applications. The design and development of geospatial applications, such as interactive maps and mobile navigation applications, has been typically founded on the expertise of surveying, cartography and geoinformatics. This has often led to relatively complex expert tools that many users find difficult to use. The research of spatial cognition can provide elementary understanding about human thinking in the use situations of these applications and supplement the knowledge gained using the usability research. Perception of landmarks along routes in nature was studied in season and time-of-day studies with participants who walked nature trails in summer, winter, day and night while thinking aloud about the surroundings. The recall of the route was measured afterwards using sketch-map drawing and photo recognition tasks. The think-aloud protocols were analysed using classification of propositions and natural language processing. The importance of landmarks for the human route perception in nature was confirmed. “Structures”, “Passages” and “Waters” were the most perceived landmark groups. Season and time-of-day significantly affected landmark perception and, based on the results, the adaptivity of geospatial applications in the studied conditions can be improved. The transfer of the empirically acquired knowledge of the landmark perception to geoinformatics was illustrated with a formal landmark ontology for hiking in nature. The measures of landmark recall were found unexpectedly similar in all the studied conditions. The similarity was explained by the salience of landmarks in nature and the structure of route-like sketch maps but also by the participants’ conceptions on what should be drawn on maps. “Passages” and “Structures” were the most-often drawn landmark groups on the sketch maps. Support of geospatial images for wayfinding was evaluated using a literaturebased evaluation framework. Visualisation of elevation was experimented with by rendering a 3D map, a derivative of which was compared to 2D elevation visualisations in an eye-tracking study. Vertical elements and elevation were found to be central wayfinding elements in geo-images and the aerial oblique vantage point the most effective image parameter for transferring spatial knowledge. The rendered 3D map was evaluated as cognitively demanding to look at but, however, showed potential in representing the terrain relief. The dissertation also considers challenges in the application of the methods of spatial cognition research and identifies directions for future studies. Note de contenu : 1. Introduction
2. Literature review
3. Methods
4. Results
5. Discussion and conclusionsNuméro de notice : 14878 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère Note de thèse : PhD thesis : Science in Technology : Aalto University School of Engineering : 2014 En ligne : https://aaltodoc.aalto.fi/handle/123456789/14049 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75988