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Evaluating airborne hyperspectral imagery for rangeland assessment in south Texas / James H. Everitt in Geocarto international, vol 19 n° 3 (September - November 2004)  

Public [article]  inGeocarto international > vol 19 n° 3 (September - November 2004) . - pp 23 - 31 Titre : Evaluating airborne hyperspectral imagery for rangeland assessment in south Texas Type de document : Article/Communication Auteurs : James H. Everitt, Auteur ; C. Yang, Auteur ; M.R. Davis, Auteur Année de publication : 2004 Article en page(s) : pp 23 - 31 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] bande visible [Termes IGN] composition colorée [Termes IGN] ERDAS Imagine [Termes IGN] flore locale [Termes IGN] image hyperspectrale [Termes IGN] occupation du sol [Termes IGN] rayonnement proche infrarouge [Termes IGN] réflectance spectrale [Termes IGN] Texas (Etats-Unis) Résumé : (Auteur) Airborne hyperspectral imagery was evaluated for differentiating among rangeland ecological variables on two range sites (tight sandy loam and shallow ridge) on south Texas rangelands. Field spectroradiometric reflectance measurements made on dominant vegetation (plant species and vegetation mixtures) and soil land-use types on the two sites identified six wavelengths [five visible and one near-infrared (NIR)] where significant spectral differences occurred among the parameters. The spectral bands that corresponded to these wavelengths were extracted from the 128-band hyperspectral images obtained of each site and used to develop false color composites that were subjected to computer classifications and accuracy assessments. The bands selected for the composites included the green (498.9 nm), yellow-green (549.7 nm), orange (629.6 nm), red (651.3 nm), dark red (680.4 nm), and NIR (825.5 tim). Accuracy assessments performed on the classification maps of four false color composites of the tight sandy loam site had overall accuracies ranging from 76% to 85%; the highest accuracy was obtained from the composite made up of the NIR, red, and yellow-green bands. Accuracy assessments performed on the classification maps of three composites of the shallow ridge site had overall accuracies ranging from 74% to 77%; the highest accuracy was acquired from a composite comprised of the NIR, orange, and yellow-green bands. Overall accuracies were considered good and indicate that several band combinations can be used successfully to differentiate among, rangeland parameters in southern Texas. Key Words: remote sensing, hyperspectral imagery, reflectance, false color composite imagery, accuracy assessment. Numéro de notice : A2004-478 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106040408542314 Date de publication en ligne : 02/01/2008 En ligne : https://doi.org/10.1080/10106040408542314 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26996 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
059-04031	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Monitoring surface soil moisture in post-harvest rice areas using C-band radar imagery in NorthEast Thailand / S. Kaojarern in Geocarto international, vol 19 n° 3 (September - November 2004)  

Public [article]  inGeocarto international > vol 19 n° 3 (September - November 2004) . - pp 61 - 71 Titre : Monitoring surface soil moisture in post-harvest rice areas using C-band radar imagery in NorthEast Thailand Type de document : Article/Communication Auteurs : S. Kaojarern, Auteur ; Thuy Le Toan, Auteur ; M.W. Davidson, Auteur Année de publication : 2004 Article en page(s) : pp 61 - 71 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] agriculture [Termes IGN] bande C [Termes IGN] humidité du sol [Termes IGN] image ERS-SAR [Termes IGN] image radar [Termes IGN] image Radarsat [Termes IGN] rizière [Termes IGN] seuillage d'image [Termes IGN] surveillance agricole [Termes IGN] surveillance météorologique [Termes IGN] Thaïlande Résumé : (Auteur) The objective of this study is to estimate the residual surface soil moisture of rice fields after harvesting, in Northeast Thailand, using Cband SAR images. Such information is use 1 to determine possibilities of cultivating additional shortcycle crops after the harvesting of the main rice crop. To accomplish this objective this study exploits three Cband SAR images acquired over the test area along with simultaneous ground measurements collected in support of analysis of the SAR images. The main parameters measured on the ground were: the volumetric moisture content of the soil using time domain reflectrometry (TDR), the surface roughness, using profile data, and residue cover. Other field environmental factors that might affect radar backscattering, including the topography of rice terraces (elevation, slope, and aspect), bund height between rice fields, soil types, and density of sparse tree stands were also acquired and registered to the image data. Before the analysis, the SAR images were calibrated, registered, and then filtered using multitemporal and spatial filters to reduce variability of the radar backscattering coefficient due to speckle. The measured soil moisture values were then correlated with the radar backscattering coefficients of the experimental plots and the results interpreted in terms of the main environmental factors. Varying residue cover and field aspect angles were found to significantly affect the relationship between radar backscatter and soil moisture content and therefore had to be taken into account before inverting the image data into soil moisture maps. Overall it was found that two soil moisture classes could reliably be separated using the SAR images, and that soil moisture maps could be obtained through a simple inversion technique based on applying a threshold to the SAR images. Analyses of these resulting moisture maps indicate that SAR data is useful to monitor and map surface soil moisture in rice fields after harvest. Numéro de notice : A2004-479 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106040408542319 Date de publication en ligne : 02/01/2008 En ligne : https://doi.org/10.1080/10106040408542319 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26997 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
059-04031	RAB	Revue	Centre de documentation	En réserve L003	Disponible