Search results for "SPECTRA"
showing 10 items of 3542 documents
Saliency-Based Band Selection For Spectral Image Visu- alization
2011
International audience; In this paper, we introduce a new band selection ap- proach for the color visualization of spectral images. Un- like traditional methods, we propose to make a selection out of a comparison of the saliency maps of the individual spectral channels. This allows to assess how different they are in terms of prominent features. A comparison metric based on Shannon's information theory at the second and third order is presented and results are subjectively and ob- jectively compared to other dimensionality reduction tech- niques on three datasets, demonstrating the efficiency of the proposed approach.
L'imagerie multispectrale embarquée pour caractériser la croissance et l'état sanitaire du feuillage de la vigne
2015
Multispectral imaging systems are widely used in remote sensing and applied to viticulture context for the canopy characterization. This technique is not used in proximal sensing, to characterize vineyard foliage. Yet the results of field tests led in fixed position have revealed its capacity to estimate the leaf area. The aim of this project is to assess the suitable of a multispectral imaging system as an embedded sensor for vine foliage characterization. To this end, a multispectral camera acquiring visible and near-infrared images and a Greenseeker RT-100 apparatus providing an NDVI (Normalized Difference Vegetation Index), were installed on a track laying tractor. It was equipped with …
Saliency in spectral images
2011
International audience; Even though the study of saliency for color images has been thoroughly investigated in the past, very little attention has been given to datasets that cannot be displayed on traditional computer screens such as spectral images. Nevertheless, more than a means to predict human gaze, the study of saliency primarily allows for measuring infor- mative content. Thus, we propose a novel approach for the computation of saliency maps for spectral images. Based on the Itti model, it in- volves the extraction of both spatial and spectral features, suitable for high dimensionality images. As an application, we present a comparison framework to evaluate how dimensionality reduct…
Asserting the Precise Position of 3D and Multispectral Acquisition Systems for Multisensor Registration Applied to Cultural Heritage Analysis
2012
International audience; We present a novel method to register multispectral acquisitions on a 3D model. The method is based on the external tracking of the acquisition systems using close-range photogrammetric techniques: multiple calibrated cameras simultaneously observe the successive acquisition systems in use. The views from these cameras are used to precisely determine the position of each acquisition system. All datasets can then be projected in the same coordinate system. The registration is thus independent from the quality and content of the data. This method is well suited to the study of cultural heritage or any other application where we do not wish to place targets on the objec…
Registration of 3D and Multispectral Data for the Study of Cultural Heritage Surfaces
2013
International audience; We present a technique for the multi-sensor registration of featureless datasets based on the photogrammetric tracking of the acquisition systems in use. This method is developed for the in situ study of cultural heritage objects and is tested by digitizing a small canvas successively with a 3D digitization system and a multispectral camera while simultaneously tracking the acquisition systems with four cameras and using a cubic target frame with a side length of 500 mm. The achieved tracking accuracy is better than 0.03 mm spatially and 0.150 mrad angularly. This allows us to seamlessly register the 3D acquisitions and to project the multispectral acquisitions on th…
Reconstruction of hyperspectral cutaneous data from an artificial neural network-based multispectral imaging system.
2011
International audience; The development of an integrated MultiSpectral Imaging (MSI) system yielding hyperspectral cubes by means of artificial neural networks is described. The MSI system is based on a CCD camera, a rotating wheel bearing a set of seven interference filters, a light source and a computer. The resulting device has been elaborated for in vivo imaging of skin lesions. It provides multispectral images and is coupled with a software reconstructing hyperspectral cubes from multispectral images. Reconstruction is performed by a neural network-based algorithm using heteroassociative memories. The resulting hyperspectral cube provides skin optical reflectance spectral data combined…
Weed detection by aerial imaging: impact of soil, crop and weed spectral mixing
2015
International audience; This study aims to evaluate spectral information potential of images captured with a UAV, for site specific weed management. The image acquisition chain was modeled in order to compute the digital values of image pixels, according to the field conditions and objects lying on the ground surface projected in the pixels. The object spectra are mixed in the same pixel to estimate the impact of the spatial resolution of the image. The classification potential into crop, weed and soil classes was studied usinf simulations based on the present multispectral sensor characteristics and according to different mixing rates.
A classification approach to prostate cancer localization in 3T Multi-Parametric MRI
2016
International audience; Multiparametric-magnetic resonance imaging (mp-MRI) has demonstrated, in many studies, its potential in prostate cancer detection and analysis. We propose a supervised classification approach based on mp-MRI data base of 20 patients, in order to localize prostate cancer and to achieve a cartographic representation of the prostate voxels based on classification results. Proposed method provides a computer aided detection (CAD) software for prostatic cancer. For that, we have extracted varied features providing functional, anatomical and metabolic information helping the classifier to distinguish between three different classes ("Healthy", "Benign" and "Pathologic"). W…
Analyse et Estimations Spectrales des Processus alpha-Stables non-Stationnaires
2006
In this work a new spectral representation of a symmetric alpha-stable processes is introduced. It is based on a covariation pseudo-additivity and Morse-Transue's integral with respect to a bimesure built by using pseudo-additivity property. This representation, specific to S$\alpha$S processes, is analogous to the covariance of second order processes. On the other hand, it generalizes the representation established for stochastic integrals with respect to symmetric alpha-stable process of independent increments. We provide a classification of non-stationary harmonizable processes; this classification is based on the bimesure structure. In particular, we defined and investigated periodicall…
Computational approach to compact Riemann surfaces
2017
International audience; A purely numerical approach to compact Riemann surfaces starting from plane algebraic curves is presented. The critical points of the algebraic curve are computed via a two-dimensional Newton iteration. The starting values for this iteration are obtained from the resultants with respect to both coordinates of the algebraic curve and a suitable pairing of their zeros. A set of generators of the fundamental group for the complement of these critical points in the complex plane is constructed from circles around these points and connecting lines obtained from a minimal spanning tree. The monodromies are computed by solving the defining equation of the algebraic curve on…