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Short-term response of Arctic vegetation NDVI to temperature anomalies / I. Olthof in International Journal of Remote Sensing IJRS, vol 28 n° 21-22 (November 2007)  

Public [article]  inInternational Journal of Remote Sensing IJRS > vol 28 n° 21-22 (November 2007) . - pp 4823 - 4840 Titre : Short-term response of Arctic vegetation NDVI to temperature anomalies Type de document : Article/Communication Auteurs : I. Olthof, Auteur ; R. Latifovic, Auteur Année de publication : 2007 Article en page(s) : pp 4823 - 4840 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] anomalie thermique [Termes IGN] Arctique [Termes IGN] Canada [Termes IGN] changement climatique [Termes IGN] détection de changement [Termes IGN] Normalized Difference Vegetation Index [Termes IGN] surveillance de la végétation Résumé : (Auteur) The effects of climate change on northern vegetation productivity need to be fully understood in order to reduce uncertainties in predicting vegetation distributions under different climate warming scenarios. Knowledge of the relationship between northern climate and vegetation productivity will also help provide a better understanding of changes in vegetation distributions as an indicator of climate change and variability. Vegetation productivity and biomass have been monitored using long-term satellite earth observations, mostly using the Normalized Difference Vegetation Index (NDVI), as a cumulative indicator of all effects resulting from processes related to climate change, including changes in temperature, precipitation, and disturbance. In this paper, the investigation is focused on the short-term effect of temperature anomalies on arctic and tree-line transition vegetation productivity in both dry and humid regions of Canada. The analysis shows that several land-cover types composed mainly of trees and shrubs exhibit a significant increase in NDVI with higher-than-normal temperatures in the preceding 10-40-day period, while land-cover types consisting of lichen and moss growing on mostly barren surfaces show a significant NDVI decrease with increased temperature. These trends are consistent with results reported in plot-warming experiments in the north, which have shown that certain vegetation communities increase, while others decrease in cover fraction and biomass in response to warming. When land cover is grouped into increasing and decreasing NDVI with temperature and stratified by dry and humid regions of Canada, much of the dry region of northern Canada does not exhibit significant NDVI response to preceding temperature anomalies. It is expected that in the absence of disturbance or other limiting factors, an increased frequency of elevated temperature anomalies may eventually contribute to changes in vegetation biomass. A map of land-cover types that have the potential to increase in biomass with climate warming and those that are vulnerable to decline is presented. Copyright Taylor & Francis Numéro de notice : A2007-491 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01431160701268996 En ligne : https://doi.org/10.1080/01431160701268996 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28854 [article]

Exemplaires(1)

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A method for detecting large-scale forest covers change using coarse spatial resolution imagery / R.H. Fraser in Remote sensing of environment, vol 95 n° 4 (30/04/2005)  

Public [article]  inRemote sensing of environment > vol 95 n° 4 (30/04/2005) . - pp 414 - 427 Titre : A method for detecting large-scale forest covers change using coarse spatial resolution imagery Type de document : Article/Communication Auteurs : R.H. Fraser, Auteur ; A. Abuelgasim, Auteur ; R. Latifovic, Auteur Année de publication : 2005 Article en page(s) : pp 414 - 427 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] Canada [Termes IGN] classificateur paramétrique [Termes IGN] classification par arbre de décision [Termes IGN] couvert forestier [Termes IGN] détection de changement [Termes IGN] données auxiliaires [Termes IGN] grande échelle [Termes IGN] image à basse résolution [Termes IGN] image à moyenne résolution [Termes IGN] image NOAA-AVHRR [Termes IGN] image SPOT-Végétation [Termes IGN] modèle de régression [Termes IGN] régression [Termes IGN] surveillance forestière Résumé : (Auteur) Many large countries, including Canada, rely on earth observation as a practical and cost-effective means of monitoring their vast inland ecosystems. A potentially efficient approach is one that detects vegetation changes over a hierarchy of spatial scales ranging from coarse to fine. This paper presents a Change Screening Analysis Technique (Change-SAT) designed as a coarse filter to identify the location and timing of large (>5-1 0 kM2) forest cover changes caused by anthropogenic and natural disturbances at an annual, continental scale. The method uses change metrics derived from 1-km multi-temporal SPOT VEGETATION and NOAA AVHRR imagery (reflectance, temperature, and texture information) and ancillary spatial variables (proximity to active fires, roads, and forest tenures) in combination with logistic regression and decision tree classifiers. Major forest changes of interest include wildfires, insect defoliation, forest harvesting and flooding. Change-SAT was tested for 1998-2000 using an independent sample of change and no-change sites over Canada. Overall accuracy was 94% and commission error, especially critical for large-area change applications, was less than 1%. Regions identified as having major or widespread changes could be targeted for more detailed investigation and mapping using field visits, aerial survey or fine resolution EO methods, such as those being applied under Canadian monitoring programs. This multi-resolution approach could be used as pan of a forest monitoring system to report on carbon stocks and forest stewardship. Numéro de notice : A2005-186 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2004.12.014 En ligne : https://doi.org/10.1016/j.rse.2004.12.014 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27323 [article]

Landsat-7 ETM+ radiometric normalization comparison for northern mapping application / I. Olthof in Remote sensing of environment, vol 95 n° 3 (15/04/2005)  

Public [article]  inRemote sensing of environment > vol 95 n° 3 (15/04/2005) . - pp 388 - 398 Titre : Landsat-7 ETM+ radiometric normalization comparison for northern mapping application Type de document : Article/Communication Auteurs : I. Olthof, Auteur ; D. Pouliot, Auteur ; R. Fernandes, Auteur ; R. Latifovic, Auteur Année de publication : 2005 Article en page(s) : pp 388 - 398 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] analyse comparative [Termes IGN] cartographie numérique [Termes IGN] correction radiométrique [Termes IGN] image Landsat-ETM+ [Termes IGN] image SPOT-Végétation [Termes IGN] méthode robuste [Termes IGN] mosaïque d'images [Termes IGN] propagation d'erreur [Termes IGN] régression Résumé : (Auteur) Relative radiometric normalization has long been performed to generate consistency among individual Landsat scenes for production of composites containing multiple scenes. Normalization methods have relied on matching identical and assumed invariant features in both images of an overlapping pair, or on invariant targets that are not necessarily the same features. Problems with overlap normalization methods include sensitivity to outliers in overlap data caused by atmospheric or land cover change between scenes, which can lead to radiometric error propagation across a mosaic caused by a normalized scene becoming a reference for the subsequent scene entered into the mosaic. Solutions to such problems include interactive outlier removal to generate a normalization function using a 'no change' data set and methods that are robust against outliers to automatically generate normalization functions with minimal user input. This paper compares two normalization methods that use a robust regression technique called Theil-Sen with an established overlap normalization method. The first method uses Theil-Sen regression to generate a normalization function between overlap regions, while the second uses Theil-Sen to normalize to coarse-resolution composite reflectance data from the SPOT VEGETATION (VGT) sensor. The results of the normalizations were evaluated in two ways: (1) using statistics generated between overlap regions; and (2) separately using coarse-resolution data as a reference. Both overlap normalization methods performed almost identically; however, Theil-Sen was faster and easier to implement than its traditional counterpart due to its insensitivity to outliers and capability for full automation. While overlap and coarse-resolution normalizations each outperformed the other when evaluated against its calibration set, error propagation caused by outliers in overlap samples was avoided in the normalization to coarse-resolution imagery. Advantages offered by normalization to coarse-resolution data using robust regression, including full automation, make this method particularly attractive for generation of large area mosaics containing 100 Landsat scenes or more. Numéro de notice : A2005-171 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2004.06.024 En ligne : https://doi.org/10.1016/j.rse.2004.06.024 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27309 [article]

Systematic corrections of AVHRR image composites for temporal studies / J. Cihlar in Remote sensing of environment, vol 89 n° 2 (30/01/2004)  

Public [article]  inRemote sensing of environment > vol 89 n° 2 (30/01/2004) . - pp 217 - 233 Titre : Systematic corrections of AVHRR image composites for temporal studies Type de document : Article/Communication Auteurs : J. Cihlar, Auteur ; R. Latifovic, Auteur ; et al., Auteur Année de publication : 2004 Article en page(s) : pp 217 - 233 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] analyse comparative [Termes IGN] correction d'image [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] image en couleur composée [Termes IGN] image Landsat-TM [Termes IGN] image NOAA-AVHRR [Termes IGN] réflectance végétale Résumé : (Auteur) For quantitative studies of vegetation dynamics, satellite data need to be corrected for spurious effects. In this study, we have applied several changes to an earlier advanced very high resolution radiometer (AVHRR) processing methodology (ABC3; [Remote Sens. Environ. 60 (1997) 35; J. Geophys. Res.Atmos, 102 (1997) 29625; Can. J. Remote Sens. 23 (1997) 163]), to better represent the various physical processes causing contamination of the AVHRR measurements. These included published recent estimates of the NOAA-11 and NOAA-14 AVHRR calibration trajectories for channels 1 and 2; the best available estimates for the water vapour, aerosol and ozone amounts at the time of AVHRR data acquisition; an improved bidirectional reflectance algorithm that also takes into consideration surface topography; and an improved image screening algorithm for contaminated pixels. Unlike the previous study that compared the composite images to a single-date AVHRR image, we employed coincident TM images to approximate the AVHRR pixel field of view during the data acquisition. Compared to ABC3, the modified procedure ABOV2 was found to improve the accuracy of AVHRR pixel reflectance estimates, both in the sensitivity (slope) of the regression and in r2. The improvements were especially significant in AVHRR channel 1. In comparison with reference values derived from two full TM scenes, the corrected AVHRR surface reflectance estimates had average standard errors values of + 0.009 for AVHRR C1, + 0.019 for C2, and + 0.04 for NDVI; the corresponding r2 values were 0.55, 0.80, and 0.50, respectively. The changes in ABC3V2 were not able to completely remove interannual variability for land cover types with little or no vegetation cover, which would be expected to remain stable over time, and they increased the interannual variability of mixed forest and grassland. These results are attributed to a combination of increased sensitivity to interannual dynamics on one hand, and the inability to remove all sources of noise for barren or sparsely vegetated northern land cover types on the other. Numéro de notice : A2004-025 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2002.06.007 En ligne : https://doi.org/10.1016/j.rse.2002.06.007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26553 [article]

A comparison of BRDF models for the normalization of satellite optical data to a standard sun-target-sensor geometry / R. Latifovic in IEEE Transactions on geoscience and remote sensing, vol 41 n° 8 (August 2003)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 41 n° 8 (August 2003) . - pp 1889 - 1898 Titre : A comparison of BRDF models for the normalization of satellite optical data to a standard sun-target-sensor geometry Type de document : Article/Communication Auteurs : R. Latifovic, Auteur ; J. Cihlar, Auteur ; J. Chen, Auteur Année de publication : 2003 Article en page(s) : pp 1889 - 1898 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] analyse comparative [Termes IGN] changement climatique [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] éclairement lumineux [Termes IGN] image NOAA-AVHRR [Termes IGN] image optique [Termes IGN] image SPOT-Végétation [Termes IGN] rayonnement solaire [Termes IGN] réflectance de surface [Termes IGN] tâche claire Résumé : (Auteur) Climate change studies require consistent, long time series, surface reflectance data. The characterization of the bidirectional reflectance distribution function (BRDF) is important for normalizing the solar radiation reflected from the earth's surface. We evaluated four BRDF models to identify the preferred approach to the normalization of multiyear National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (AVHRR) and SPOT4VEGETATION (VGT) composite images to a common illumination and viewing geometry. Four models by the following authors were included: Walthall, Ropjean, Ross-Li, and a new nonlinear temporal angular model (NTAM). NTAM accounts for hotspot effects and also responds to seasonal changes in land cover properties (using vegetation indexes as surrogate temporal measures). We compared the performance of the models under different scenarios of coefficient derivation and model application including model ability to reproduce theoretical BRDF curves, model consistency in single, multiyear, and incomplete sampling schemes, and comparison of AVMR and LANDSAT Thematic Mapper surface reflectance prior and after BRDF normalization. We found that in all the tests, NTAM yielded the best fits between the observed and estimated values. NTAM requires eight coefficients and a lengthier iterative procedure to derive the coefficients, but the resulting coefficients are applied to the entire growing season rather than one temporal window. NTAM also performed well for different sensors (AVHRR, VGT) and geographic areas (Canada, east Asia, southern United States). Our results contradict the often-encountered perception that semiempirical BRDF models for angular normalization are all similarly effective, and the research on this topic is mature. We also describe a procedure for routine normalization of satellite optical data. For northern ecosystems, the NTAM coefficients derived from AVHRR and VGT data for Canada are available via ftp://Ccrs.nrcan.gc.ca. Numéro de notice : A2003-280 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2003.811557 En ligne : https://doi.org/10.1109/TGRS.2003.811557 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22575 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
065-03081	RAB	Revue	Centre de documentation	En réserve L003	Disponible