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Geospatial data organization methods with emphasis on aperture-3 hexagonal discrete global grid systems / Ali Mahdavi Amiri in Cartographica, vol 54 n° 1 (spring 2019)  

Public [article]  inCartographica > vol 54 n° 1 (spring 2019) . - pp 30 - 50 Titre : Geospatial data organization methods with emphasis on aperture-3 hexagonal discrete global grid systems Type de document : Article/Communication Auteurs : Ali Mahdavi Amiri, Auteur ; Troy Alderson, Auteur ; Faramarz Samavati, Auteur Année de publication : 2019 Article en page(s) : pp 30 - 50 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes descripteurs IGN] arbre de décision [Termes descripteurs IGN] données vectorielles [Termes descripteurs IGN] méthode des moindres carrés [Termes descripteurs IGN] ondelette de Haar [Termes descripteurs IGN] régression [Termes descripteurs IGN] système de grille globale discrète [Termes descripteurs IGN] transformation en ondelettes Résumé : (Auteur) Digital Earth frameworks deal with data sets of different types collected from various sources. To effectively store, retrieve, and transmit these data sets, efficient multi-scale data representations that are compatible with the underlying structure of the Digital Earth framework are required. In this article, we describe several such techniques and their properties: namely, how to represent data in the multi-scale cell hierarchy of a discrete global grid system (DGGS) or in the multi-scale hierarchy of a customized wavelet transform. We also discuss how these techniques can be tuned to be applicable to the A3H DGGS. Numéro de notice : A2019-435 Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.3138/cart.54.1.2018-0010 En ligne : https://doi.org/10.3138/cart.54.1.2018-0010 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92761 [article]

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Denoising of natural images through robust wavelet thresholding and genetic programming / Asem Khmag in The Visual Computer, vol 33 n°9 (September 2017)  

Public [article]  inThe Visual Computer > vol 33 n°9 (September 2017) . - pp 1141 - 1154 Titre : Denoising of natural images through robust wavelet thresholding and genetic programming Type de document : Article/Communication Auteurs : Asem Khmag, Auteur ; Abd Rahman Ramli, Auteur ; S.A.R. Al-haddad, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 1141 - 1154 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes descripteurs IGN] algorithme génétique [Termes descripteurs IGN] bruit blanc [Termes descripteurs IGN] filtrage du bruit [Termes descripteurs IGN] ondelette [Termes descripteurs IGN] seuillage d'image Résumé : (auteur) Digital images play an essential role in analysis tasks that can be applied in various knowledge domains, including medicine, meteorology, geology, and biology. Such images can be degraded by noise during the process of acquisition, transmission, storage, or compression. The use of local filters in image restoration may generate artifacts when these filters are not well adapted to the image content as a result of the heuristic optimization of local filters. Denoising methods based on learning procedure are more capable than parametric filters for addressing the conflicts between noise suppression and artifact reduction. In this study, we present a nonlinear filtering method based on a two-step switching scheme to remove both salt-and-pepper and additive white Gaussian noises. In the switching scheme, two cascaded detectors are used to detect noise, and two corresponding estimators are employed to effectively and efficiently filter the noise in an image. In the process of training, a method according to patch clustering is utilized, and genetic programming (GP) is subsequently applied to determine the optimum filter (wavelet-domain filter) for each individual cluster, while in testing part, the optimum filter trained beforehand by GP is recovered and used on the inputted corrupted patch. This adaptive structure is employed to cope with several noise types. Experimental and comparative analysis results show that the denoising performance of the proposed method is superior to that of existing denoising methods as per both quantitative and qualitative assessments. Numéro de notice : A2017-407 Thématique : IMAGERIE/INFORMATIQUE Nature : Article En ligne : https://doi.org/10.1007/s00371-016-1273-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86288 [article]

WREP : A wavelet-based technique for extracting the red edge position from reflectance spectra for estimating leaf and canopy chlorophyll contents of cereal crops / Dong Li in ISPRS Journal of photogrammetry and remote sensing, vol 129 (July 2017)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 129 (July 2017) . - pp 103 - 117 Titre : WREP : A wavelet-based technique for extracting the red edge position from reflectance spectra for estimating leaf and canopy chlorophyll contents of cereal crops Type de document : Article/Communication Auteurs : Dong Li, Auteur ; Tao Cheng, Auteur ; Kai Zhou, Auteur Année de publication : 2017 Article en page(s) : pp 103 - 117 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes descripteurs IGN] bande rouge [Termes descripteurs IGN] canopée [Termes descripteurs IGN] céréales [Termes descripteurs IGN] cultures [Termes descripteurs IGN] ondelette [Termes descripteurs IGN] rayonnement proche infrarouge [Termes descripteurs IGN] réflectance spectrale [Termes descripteurs IGN] teneur en chlorophylle des feuilles [Termes descripteurs IGN] transformation en ondelettes Résumé : (Auteur) Red edge position (REP), defined as the wavelength of the inflexion point in the red edge region (680–760 nm) of the reflectance spectrum, has been widely used to estimate foliar chlorophyll content from reflectance spectra. A number of techniques have been developed for REP extraction in the past three decades, but most of them require data-specific parameterization and the consistence of their performance from leaf to canopy levels remains poorly understood. In this study, we propose a new technique (WREP) to extract REPs based on the application of continuous wavelet transform to reflectance spectra. The REP is determined by the zero-crossing wavelength in the red edge region of a wavelet transformed spectrum for a number of scales of wavelet decomposition. The new technique is simple to implement and requires no parameterization from the user as long as continuous wavelet transforms are applied to reflectance spectra. Its performance was evaluated for estimating leaf chlorophyll content (LCC) and canopy chlorophyll content (CCC) of cereal crops (i.e. rice and wheat) and compared with traditional techniques including linear interpolation, linear extrapolation, polynomial fitting and inverted Gaussian. Our results demonstrated that WREP obtained the best estimation accuracy for both LCC and CCC as compared to traditional techniques. High scales of wavelet decomposition were favorable for the estimation of CCC and low scales for the estimation of LCC. The difference in optimal scale reveals the underlying mechanism of signature transfer from leaf to canopy levels. In addition, crop-specific models were required for the estimation of CCC over the full range. However, a common model could be built with the REPs extracted with Scale 5 of the WREP technique for wheat and rice crops when CCC was less than 2 g/m2 (R2 = 0.73, RMSE = 0.26 g/m2). This insensitivity of WREP to crop type indicates the potential for aerial mapping of chlorophyll content between growth seasons of cereal crops. The new REP extraction technique provides us a new insight for understanding the spectral changes in the red edge region in response to chlorophyll variation from leaf to canopy levels. Numéro de notice : A2017-348 Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2017.04.024 En ligne : https://dx.doi.org/10.1016/j.isprsjprs.2017.04.024 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85616 [article]

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Multi-scale modeling of Earth's gravity field in space and time / Shuo Wang in Journal of geodynamics, vol 106 (May 2017)  

Public [article]  inJournal of geodynamics > vol 106 (May 2017) . - pp 46 - 65 Titre : Multi-scale modeling of Earth's gravity field in space and time Type de document : Article/Communication Auteurs : Shuo Wang, Auteur ; Isabelle Panet , Auteur ; Guillaume L. Ramilien, Auteur ; Frédéric Guilloux, Auteur Année de publication : 2017 Projets : 1-Pas de projet / Article en page(s) : pp 46 - 65 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] champ de pesanteur terrestre [Termes descripteurs IGN] données 4D [Termes descripteurs IGN] données GRACE [Termes descripteurs IGN] modèle de géopotentiel [Termes descripteurs IGN] ondelette [Termes descripteurs IGN] problème inverse Résumé : (auteur) Since 2002, the GRACE mission has been providing an unprecedented view of the Earth's gravity field spatial and temporal variations. The gravity field models built from these satellite data are essential in order to study the mass redistributions within the Earth system. Often, they are modelled using spatial functions, such as spherical harmonics, averaged over a fixed time window. However, the satellite sampling naturally leads to a trade-off between the achievable spatial and temporal resolutions. In addition, the gravity variations are made of local components in space and time, reflecting the superimposition of sources. With the final aim to better estimate gravity variations related to local processes at different spatial and temporal scales, and adapt the temporal resolution of the model to its spatial resolution, we present an attempt at 4D gravity field modelling using localized functions in space and time. For that, we develop a four-dimensional wavelet basis, well localized in space and time and orthogonal in time. We then analyze the inverse problem of 4D gravity field estimation from GRACE synthetic inter-satellites potential differences along the orbit, and its regularization in a Bayesian framework, using a prior knowledge on the mass sources. We then test our approach in a simplified synthetic test setting, where only one mass source is present: hydrological mass variations over Africa during the year 2005. Applying a purely regional approach, we are able to reconstruct, regionally, the water height signal with a ≈2.5 cm accuracy at 450 km, 21 days resolution. We test the influence of the geophysical prior on this result, and conclude that it cannot explain alone the residuals between original and reconstructed mass signal. redIn contrast, an ideal test case with a perfect adequacy between the 4D basis and the synthetic data, without approximations nor regularization in solving the normal system, leads to a significantly improved reconstruction of large-scale, seasonal water variations, at the millimetric level of a few % of relative accuracy. The performances of the regional test are likely significantly limited by the block-diagonal approximation of the normal system and the scales selection in the regional 4D basis. Numéro de notice : A2017-869 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jog.2017.02.001 date de publication en ligne : 20/02/2017 En ligne : https://doi.org/10.1016/j.jog.2017.02.001 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89895 [article]

Evaluation of pan-sharpening methods for spatial and spectral quality / Jagalingam Pushparaj in Applied geomatics, vol 9 n° 1 (March 2017)  

Public [article]  inApplied geomatics > vol 9 n° 1 (March 2017) . - pp 1 - 12 Titre : Evaluation of pan-sharpening methods for spatial and spectral quality Type de document : Article/Communication Auteurs : Jagalingam Pushparaj, Auteur ; Arkal Vittal Hegde, Auteur Année de publication : 2017 Article en page(s) : pp 1 - 12 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes descripteurs IGN] algorithme de Gram-Schmidt [Termes descripteurs IGN] analyse en composantes principales [Termes descripteurs IGN] classification Spectral angle mapper [Termes descripteurs IGN] évaluation [Termes descripteurs IGN] filtre passe-haut [Termes descripteurs IGN] image multibande [Termes descripteurs IGN] image panchromatique [Termes descripteurs IGN] image Quickbird [Termes descripteurs IGN] ondelette [Termes descripteurs IGN] pansharpening (fusion d'images) [Termes descripteurs IGN] qualité géométrique (image) [Termes descripteurs IGN] qualité radiométrique (image) [Termes descripteurs IGN] transformation de Brovey [Termes descripteurs IGN] transformation intensité-teinte-saturation Résumé : (auteur) Many pan-sharpening methods have been proposed to fuse the high spectral and low spatial resolution of multispectral (MS) image with the high spatial resolution of panchromatic (PAN) image to produce a multispectral image with improved spatial resolution. In this study, the effectiveness of pan-sharpening methods such as principal component analysis (PCA), brovey transform (BT), modified intensity hue saturation (M-IHS), multiplicative, wavelet-intensity-hue-saturation (W-IHS), wavelet principal component analysis (W-PCA), hyperspectral colour space (HCS), high-pass filter (HPF), gram-schmidt (GS), subtractive resolution merge (SRM), Fuze Go and Ehlers was assessed and compared by fusing the PAN and MS imagery of Quickbird-2. The qualities of the pan-sharpening methods were evaluated by both visual and quantitative analyses with respect to spatial and spectral fidelity. In quantitative analysis, the spectral indices such as spectral angle mapper (SAM), relative dimensionless global error in synthesis (ERGAS), structural similarity index method (SSIM), relative average spectral error (RASE), correlation coefficient (CC) and universal image quality index (Q) were used. The spatial indices such as spatial correlation coefficient (SCC), gradient and image entropy (E) were used. The result of both analyses revealed that the Ehlers and Fuze Go methods performed better than the other methods. The Ehlers method was superior by retaining the colour information, and Fuze Go best enhanced the spatial details in the fused image. Numéro de notice : A2017-357 Thématique : IMAGERIE Nature : Article En ligne : http://doi.org/10.1007/s12518-016-0179-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85763 [article]

Gravity forward modeling with a tesseroid-based rock-water-ice approach / Thomas Grombein (2017)    

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Ondelettes et processus stochastiques / Abdourrahmane M. Atto (2017)

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Télédétection pour l'observation des surfaces continentales, ch. 6. Méthodes de traitement de données lidar / Clément Mallet (2017)

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Regression wavelet analysis for lossless coding of remote-sensing data / Naoufal Amrani in IEEE Transactions on geoscience and remote sensing, vol 54 n° 9 (September 2016)  

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Modeling of ionosphere time series using wavelet neural networks (case study: N-W of Iran) / Mir Reza Ghaffari Razin in Advances in space research, vol 58 n° 1 (July 2016)  

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Wavelet analysis of low-frequency variability in oak tree-ring chronologies from east Central Europe / Asok K. Sen in Open geosciences, vol 8 n° 1 (January - July 2016)  

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A wavelet-based echo detector for waveform LiDAR data / Cheng-Kai Wang in IEEE Transactions on geoscience and remote sensing, vol 54 n° 2 (February 2016)  

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Remote Sensing Observations of Continental Surfaces, ch. 6. Airborne lidar data processing / Clément Mallet (2016)  

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Gravité de la Terre : des mesures aux modèles, une image de la dynamique interne / Isabelle Panet (2015)

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Optical signal processor for millimeter-wave interferometric radiometry / Enrique Nova in IEEE Transactions on geoscience and remote sensing, vol 52 n° 5 tome 1 (May 2014)

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