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Super-resolution image analysis as a means of monitoring bracken (Pteridium aquilinum) distributions / Jennie Holland in ISPRS Journal of photogrammetry and remote sensing, vol 75 (January 2013)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 75 (January 2013) . - pp 48 - 63 Titre : Super-resolution image analysis as a means of monitoring bracken (Pteridium aquilinum) distributions Type de document : Article/Communication Auteurs : Jennie Holland, Auteur ; Paul Alpin, Auteur Année de publication : 2013 Article en page(s) : pp 48 - 63 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] analyse comparative [Termes IGN] classification dirigée [Termes IGN] Filicophyta [Termes IGN] image Ikonos [Termes IGN] image Landsat [Termes IGN] image multitemporelle [Termes IGN] plante non ligneuse [Termes IGN] surveillance de la végétation Résumé : (Auteur) The bracken (Pteridium aquilinum) fern is environmentally significant due to its great abundance and swift colonisation, and its perception as a problem plant in degrading agricultural or ecologically sensitive land. Various attempts have been made to map bracken using remote sensing, but these have proved relatively unsuccessful, often apparently constrained by the lack of spatial detail associated with medium spatial resolution satellite sensors such as the Landsat series. In this study, bracken was characterised using a combination of 30 m Landsat sensor imagery and 4 m IKONOS imagery. Different classification techniques were compared, including hard maximum likelihood classification and a super-resolution approach comprising soft classification and sub-pixel contouring. These techniques were applied to a range of image dates, including summer, winter and multitemporal images. Image analysis was supported by extensive field data collection, comprising both a land cover survey and stakeholder interviews. For the hard classified Landsat sensor imagery, the summer image proved least able to characterise bracken, due largely to the spectral similarity between (green) growing bracken and grasses and other vegetation. The winter images were more successful for identifying bracken due to the strong contrast between dead (brown/red) bracken and other vegetation. However, the multitemporal Landsat image was considerably more accurate than any of the single date images. The hard classified IKONOS image was more accurate overall than the Landsat sensor images for classifying land cover. Surprisingly, though, it was not comprehensively more accurate for mapping the bracken class. Notably, the producers accuracy of bracken was lower for the IKONOS image than the Landsat sensor images. This suggests image spatial resolution, although influential on the success of bracken characterisation, is not necessarily the sole or main determinant of classification accuracy. Also important are the temporal nature of image acquisition (here the multitemporal Landsat sensor image proved of considerable benefit) and the spectral characteristics of the imagery (here IKONOS’s four visible and near infrared spectral wavebands proved limited compared to the Landsat sensors’ six visible, near and shortwave infrared bands). Following soft classification of the multitemporal Landsat image, super-resolution sub-pixel contouring was applied to identify the boundary of bracken patches. Predicted bracken boundaries were assessed against actual boundaries identified using field observation and IKONOS image interpretation. For comparison, the bracken boundaries identified through hard classification (i.e. using pixel edges) were also assessed against the actual boundaries. Overall, the spatial accuracy of the super-resolution approach proved considerably higher than that of hard classification. Numéro de notice : A2013-032 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2012.10.002 En ligne : https://doi.org/10.1016/j.isprsjprs.2012.10.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32170 [article]

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Monitoring spatio-temporal dynamics of photosynthesis with a portable hyperspectral imaging system / U. Rascher in Photogrammetric Engineering & Remote Sensing, PERS, vol 73 n° 1 (January 2007)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 73 n° 1 (January 2007) . - pp 45 - 56 Titre : Monitoring spatio-temporal dynamics of photosynthesis with a portable hyperspectral imaging system Type de document : Article/Communication Auteurs : U. Rascher, Auteur ; C.J. Nichol, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 45 - 56 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] appareil portable [Termes IGN] fluorescence [Termes IGN] image hyperspectrale [Termes IGN] intensité lumineuse [Termes IGN] photosynthèse [Termes IGN] plante non ligneuse [Termes IGN] réflectance végétale [Termes IGN] spectromètre imageur [Termes IGN] stress hydrique [Termes IGN] surveillance de la végétation Résumé : (Auteur) Photosynthetic efficiency of higher plants dynamically adapts to changing light intensity and is greatly influenced by stress, such as water stress. We tested a new portable hyperspectral imaging system, the SOC-700, manufactured by Surface Optics, which produces 12-bit reflectance images between 440 nm and 880 nm with a 4 nm spectral resolution. We quantified the reflectance properties and photochemical reflectance index (PRI) during light adaptation of genetically modified Arabidopsis thaliana (L.) Heynh. plants lacking or over-expressing the PsbS protein, an essential component of the mechanism of non-photochemical dissipation. In a second experiment, PRI images of gradually water stressed leaves were compared to leaf-level measurements of reflectance using a second commercially available spectrometer, and chlorophyll fluorescence to detect dynamic, photosynthesis correlated changes in reflectance and PRI. In both experiments PRI measured with the SOC-700 changed, reflecting the biochemical adaptation of the photosynthetic apparatus to high light intensity (dynamic changes within minutes) and the gradual deactivation of photosynthesis during drying (changes within hours). The quantum efficiency of photosystem II (?F/Fm') and non-photochemical energy dissipation (NPQ) measured from chlorophyll fluorescence, were strongly correlated with PRI. Leaf area PRI values estimated from individual pixel spectra of the SOC-700 quantified photosynthetic efficiency more thoroughly than PRI values calculated from point measurements using the hand-held GER-1500. The applications, limitations, and potential of the SOC-700 for plant eco-physiology and remote sensing are also discussed. Copyright ASPRS Numéro de notice : A2007-011 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.73.1.45 En ligne : https://doi.org/10.14358/PERS.73.1.45 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28377 [article]