Descripteur
Documents disponibles dans cette catégorie (2824)
![](./images/expand_all.gif)
![](./images/collapse_all.gif)
Etendre la recherche sur niveau(x) vers le bas
Examining the influence of changing laser pulse repetition frequencies on conifer forest canopy returns / Laura Chasmer in Photogrammetric Engineering & Remote Sensing, PERS, vol 72 n° 12 (December 2006)
![]()
[article]
Titre : Examining the influence of changing laser pulse repetition frequencies on conifer forest canopy returns Type de document : Article/Communication Auteurs : Laura Chasmer, Auteur ; Christopher Hopkinson, Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 1359 - 1367 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] ALTM
[Termes IGN] canopée
[Termes IGN] données lidar
[Termes IGN] données multitemporelles
[Termes IGN] forêt boréale
[Termes IGN] fréquence
[Termes IGN] impulsion laser
[Termes IGN] lasergrammétrie
[Termes IGN] onde radioélectrique
[Termes IGN] Pinophyta
[Termes IGN] surface du sol
[Termes IGN] télémétrie laser aéroporté
[Termes IGN] vibrationRésumé : (Auteur) The distribution of laser pulses within conifer forest trees and canopies are examined by varying the rate of laser pulse emission and the inherent laser pulse properties (laser pulse energy, pulse width, pulse length, and roll-over or trigger time). In this study, an Optech, Inc. ALTM 3100 airborne lidar is used, emitting pulses at 50 kHz and 100 kHz, allowing for changes in laser pulse characteristics while also keeping all other survey parameters equal. We found that:
1. Pulses and associated characteristics emitted at 50 kHz penetrated further into the canopy than 100 kHz for a significant number of individual trees.
2. At tall tree plots with no understory, pulses emitted at 50 kHz penetrated further into the canopy than 100 kHz for a significant number of plots.
3. For plots with significant understory and shorter trees, pulses emitted at 100 kHz penetrated further into the canopy than 50 kHz. We suspect that this may be due, in part, to canopy openness.
Laser pulse energy and character differences associated with different laser pulse emission frequencies are likely a contributing factor in laser pulse penetration through the canopy to the ground surface. Efforts to understand laser pulse character influences on canopy returns are important as biomass and vegetation structure models derived from lidar are increasingly adopted. Copyright ASPRSNuméro de notice : A2006-544 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.14358/PERS.72.12.1359 En ligne : https://doi.org/10.14358/PERS.72.12.1359 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28267
in Photogrammetric Engineering & Remote Sensing, PERS > vol 72 n° 12 (December 2006) . - pp 1359 - 1367[article]A spectral and spatial source separation of multispectral images / M.A. Loghmari in IEEE Transactions on geoscience and remote sensing, vol 44 n° 12 (December 2006)
![]()
[article]
Titre : A spectral and spatial source separation of multispectral images Type de document : Article/Communication Auteurs : M.A. Loghmari, Auteur ; Mohamed Saber Naceur, Auteur ; Mohamed-Rached Boussema, Auteur Année de publication : 2006 Article en page(s) : pp 3659 - 3673 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] classification bayesienne
[Termes IGN] données multisources
[Termes IGN] hétérogénéité
[Termes IGN] image multibande
[Termes IGN] occupation du sol
[Termes IGN] segmentation d'image
[Termes IGN] séparabilité
[Termes IGN] signature spectraleRésumé : (Auteur) This paper deals with the problem of blind source separation of remote sensing data based on a Bayesian estimation framework. We consider the case of multispectral images in which we have observed images of the same zone through different spectral bands. The land cover types existing in the scanned zone constitute the sources to separate. Associating each source to a specific significant theme remains the real challenge in the source-separation method applied to satellite images. In fact, multispectral images consist of multiple channels, each channel containing data acquired from different bands within the frequency spectrum. Since most objects emit or reflect energy over a large spectral bandwidth, there usually exists a significant correlation between channels. This constitutes the first difficulty for sources identification. The second difficulty lies in the heterogeneity of most of the geological and vegetative ground surfaces. In this case, the geometrical projection of a single detector element at the Earth's surface, which is sometimes called the instantaneous field of view, is formed from a mixture of spectral signatures. In such circumstances, the needed information is either not available or not reliable. In this paper, the goal is to establish a new approach based on a two-level source separation (TLSS), which consists of a spectral separation along the different used bands and a spatial separation along neighboring pixels of each image band. The spectral separation has been used prior to the Bayesian approach, and it is based on a second-order statistics approach that exploits the correlation through different spectral bands of the multispectral sensor. The given images are represented according to independent axes that provide more effective representation of the information within the observation images. The spectral separation consists of identifying the sources without resorting to any a priori information, hence the term blind. The obtained source-separation represent the starting point for the Bayesian approach, which is known for its weakness in front of initial conditions. To identify a significant theme for each source, we have to spatially separate each image based on a Bayesian source-separation framework. The proposed approach has the added advantages of the blind source method as well as the Bayesian method. It should give segmented images related to each theme covering the scanned zone, which are the TLSS results of the observation images. Copyright IEEE Numéro de notice : A2006-559 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2006.882261 En ligne : https://doi.org/10.1109/TGRS.2006.882261 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28282
in IEEE Transactions on geoscience and remote sensing > vol 44 n° 12 (December 2006) . - pp 3659 - 3673[article]Réservation
Réserver ce documentExemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 065-06121 RAB Revue Centre de documentation En réserve L003 Disponible Thermal re-emission effects on GPS satellites / J. Duha in Journal of geodesy, vol 80 n° 12 (December 2006)
![]()
[article]
Titre : Thermal re-emission effects on GPS satellites Type de document : Article/Communication Auteurs : J. Duha, Auteur ; G.B. Afonso, Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 665 - 674 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] albedo
[Termes IGN] émission thermique
[Termes IGN] modèle mathématique
[Termes IGN] orbitographie
[Termes IGN] perturbation orbitale
[Termes IGN] photon
[Termes IGN] rayonnement solaire
[Termes IGN] satellite GPSRésumé : (Auteur) Highly precise satellite-derived coordinates depend on accurate orbit predictions, which cannot be achieved with purely empirical models. Global positioning system (GPS) satellites undergo several periodic perturbing forces that have to be modeled and understood. In this scenario, small non-gravitational forces can no longer be neglected when the purpose of the orbital analysis is to obtain accurate results (Vilhena de Moraes 1994). Together with solar radiation pressure, thermal re-emission effects due to solar heating and Earth albedo are the two most important non-gravitational effects. While solar radiation pressure is widely understood, our knowledge about thermal re-emission effects on GPS satellites is in its infancy. Few models have been proposed in recent years and despite the interest of the scientific community, there is a lack of detailed results concerning the magnitude and the behavior of such forces. The aim of this work is to provide a thermal re-emission force model for GPS satellites, simple enough to minimize the problem of modeling a satellite of complex shape with several components on its surface, but accurate enough to provide an estimate of the magnitude and the behavior of these forces, as well as to provide some input to the present knowledge about photon thrust on GPS satellites. Some results of this work point to the fact that thermal re-emission effects are good candidates to partially explain the Y-bias for GPS satellites. Copyright Springer Numéro de notice : A2006-538 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0060-x En ligne : https://doi.org/10.1007/s00190-006-0060-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28261
in Journal of geodesy > vol 80 n° 12 (December 2006) . - pp 665 - 674[article]Réservation
Réserver ce documentExemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 266-06111 RAB Revue Centre de documentation En réserve L003 Disponible 266-06112 RAB Revue Centre de documentation En réserve L003 Disponible Wind resource assessment from C-band SAR / M.B. Christiansen in Remote sensing of environment, vol 105 n° 1 (15/11/2006)
![]()
[article]
Titre : Wind resource assessment from C-band SAR Type de document : Article/Communication Auteurs : M.B. Christiansen, Auteur ; W Koch, Auteur Année de publication : 2006 Article en page(s) : pp 68 - 81 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] analyse comparative
[Termes IGN] bande C
[Termes IGN] direction
[Termes IGN] écart type
[Termes IGN] erreur systématique
[Termes IGN] gradient
[Termes IGN] image Envisat-ASAR
[Termes IGN] image ERS-SAR
[Termes IGN] Nord, mer du
[Termes IGN] vent
[Termes IGN] vitesseRésumé : (Auteur) Using accurate inputs of wind speed is crucial in wind resource assessment, as predicted power is proportional to the wind speed cubed. First, wind speeds retrieved from a series of 91 ERS-2 SAR and Envisat ASAR images, at moderate wind speeds (2–15 m s- 1), were validated against in situ measurements from an offshore mast in the North Sea. The wind direction input, necessary for SAR wind speed retrievals, was obtained from the meteorological mast and from a local gradient analysis of wind streaks in the SAR images. A wind speed standard deviation of not, vert, similar 1.1 m s- 1 was found when in situ wind directions were used. The use of local gradient wind directions yielded a standard deviation of not, vert, similar 1.3 m s- 1. Wind speeds retrieved from three geophysical model functions (CMOD-IFR2, CMOD4, and CMOD5) were compared. The best approximation to the in situ measurements of wind speed was found for CMOD-IFR2, despite a bias on the order of - 0.3 m s- 1. CMOD4 retrievals also underestimated the wind speed, whereas the bias on CMOD5 retrievals was negligible. Then, wind resource assessments were made from the SAR-based wind observations to show how errors in wind speed from the different SAR wind retrievals were reflected in the wind statistics. The mean wind speed, obtained for all of the 91 SAR scenes, was linked closely to the bias of SAR wind retrievals. Agreement to 1 15% of the in situ measurements was found for all the wind retrieval methods tested. The accuracy of power density estimates for the entire data set was evaluated by the standard deviation of SAR wind retrievals relative to the in situ measurements. SAR wind fields retrieved with CMOD-IFR2, using in situ wind direction inputs, exactly yielded the power density predicted from in situ measurements alone. The SAR-based wind resource assessment also corresponded well to predictions from longer time series of in situ measurements. This indicates that a reliable wind resource assessment may be achieved from a series of randomly selected SAR images. The findings presented here could be useful in future wind resource assessment based on SAR images. Copyright Elsevier Numéro de notice : A2006-503 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2006.06.005 En ligne : https://doi.org/10.1016/j.rse.2006.06.005 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28227
in Remote sensing of environment > vol 105 n° 1 (15/11/2006) . - pp 68 - 81[article]Exploiting class hierarchies for knowledge transfer in hyperspectral data / S. Rajan in IEEE Transactions on geoscience and remote sensing, vol 44 n° 11 Tome 2 (November 2006)
![]()
[article]
Titre : Exploiting class hierarchies for knowledge transfer in hyperspectral data Type de document : Article/Communication Auteurs : S. Rajan, Auteur ; J. Ghosh, Auteur ; Melba M. Crawford, Auteur Année de publication : 2006 Article en page(s) : pp 3408 - 3417 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] classification ascendante hiérarchique
[Termes IGN] classification non dirigée
[Termes IGN] données multitemporelles
[Termes IGN] image hyperspectrale
[Termes IGN] signature spectraleRésumé : (Auteur) Obtaining ground truth for classification of remotely sensed data is time consuming and expensive, resulting in poorly represented signatures over large areas. In addition, the spectral signatures of a given class vary with location and/or time. Therefore, successful adaptation of a classifier designed from the available labeled data to classify new hyperspectral images acquired over other geographic locations or subsequent times is difficult, if minimal additional labeled data are available. In this paper, the binary hierarchical classifier is used to propose a knowledge transfer framework that leverages the information extracted from the existing labeled data to classify spatially separate and multitemporal test data. Experimental results show that in the absence of any labeled data in the new area, the approach is better than a direct application of the original classifier on the new data. Moreover, when small amounts of the labeled data are available from the new area, the framework offers further improvements through semisupervised learning mechanisms and compares favorably with previously proposed methods. Copyright IEEE Numéro de notice : A2006-528 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2006.878442 En ligne : https://doi.org/10.1109/TGRS.2006.878442 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28251
in IEEE Transactions on geoscience and remote sensing > vol 44 n° 11 Tome 2 (November 2006) . - pp 3408 - 3417[article]Réservation
Réserver ce documentExemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 065-06111B RAB Revue Centre de documentation En réserve L003 Disponible Spectral normalisation and fusion of optical sensors for the retrieval of BRDF and albedo: application to vegetation, MODIS, and MERIS data sets / O. Samain in IEEE Transactions on geoscience and remote sensing, vol 44 n° 11 Tome 1 (November 2006)
PermalinkUrban surface biophysical descriptors and land surface temperature variations / D. Weng in Photogrammetric Engineering & Remote Sensing, PERS, vol 72 n° 11 (November 2006)
PermalinkImproved estimation of aerosol optical depth from MODIS imagery over land surfaces / B. Zhong in Remote sensing of environment, vol 104 n° 4 (30/10/2006)
PermalinkIntegration of MODIS data into a simple model for the spatial distributed simulation of soil water content and evapotranspiration / Y. Zhang in Remote sensing of environment, vol 104 n° 4 (30/10/2006)
PermalinkEvaluating temporal variability in the spectral reflectance response of annual ryegrass to changes in nitrogen applications and leaching fractions / M. Baghzouz in International Journal of Remote Sensing IJRS, vol 27 n°18 - 19 - 20 (October 2006)
PermalinkEvaluation of the Oceansat-1 Multi-frequency Scanning Microwave Radiometer and its potential for soil moisture retrieval / J. Wen in International Journal of Remote Sensing IJRS, vol 27 n°18 - 19 - 20 (October 2006)
PermalinkEstimating volume change of mountain glaciers using SRTM and map-based topographic data / A.B. Surazakov in IEEE Transactions on geoscience and remote sensing, vol 44 n° 10 Tome 2 (October 2006)
PermalinkLandsat-7 long-term acquisition plan radiometry: evolution over the time / B. Markham in Photogrammetric Engineering & Remote Sensing, PERS, vol 72 n° 10 (October 2006)
PermalinkRemote sensing image-based analysis of the relationship between urban heat island and land use/cover changes / X.L. Chen in Remote sensing of environment, vol 104 n° 2 (30 September 2006)
PermalinkDetection of forest decline using Ikonos sensor for cork oak (Quercus suber l.) woods in south Spain / F. Cano in Geocarto international, vol 21 n° 3 (September - November 2006)
Permalink