1,825,304 research outputs found
CIRAD-SAR. Revue externe à mi-parcours
No full textDocuments disponibles : - Schéma pluriannuel de programmation, bilan et perspectives, - Démarche en partenariat du Cirad-Sar (Groupe de travail de la direction), - La gestion de la qualité (Direction scientifique), - Ressources humaines, - Tendances et évolution de la recherche-développement agricole, la vision du Cirad-Sar (J.P.Tonneau, J.Y. Jamin, J. Faye), - La gestion de terroirs au Cirad-Sar (Document coordonné par A. Teyssier), - Les organisations paysannes, acteurs du développement (M.R. Mercoiret, P.M. Bosc), - Importance de l'énergie biomasse dans les pays en développement (G. Vaitilingom), - La mécanisation au Cirad-Sar, bilan et perspectives, - Le conseil technique aux exploitations agricoles, présentation d'une démarche d'aide à la décision (P.Y. Le Gal, Unité de recherche GAM Génie agronomique et mécanisation), - Le conseil de gestion aux petites exploitations agricoles tropicales, bilan général depuis 1970 et nouvelles perspectives (Unité de recherche ESRU Economie des systèmes ruraux), - L'économie de la mécanisation, mise au point et nouvelles orientations pour les prochaines années (Unité de recherche ESRU Economie des systèmes ruraux), - Démarche recherche-développement dans le domaine agroalimentaire, recueil de documents (Unité de recherche ISAA Innovations dans les systèmes agricoles et agroalimentaires et sciences de la consommation). Plus les bilans 1992-1994 - pour chaque programme (Développement local et dynamiques institutionnelles, Défis alimentaires urbains et promotion des entreprises, Dynamiques agraires en situations sèches et irriguées, Développement durable en savanes et tropiques humides), - pour chaque unité de recherche (GAM Génie agronomique et mécanisation, CEEI Conception des équipements énergie et métrologie, GTA Génie et technologies agroalimentaires, ISAA Innovations dans les systèmes agricoles et agroalimentaires), - et les services (Informatique et biométrie, Edition
F-SAR – DLR’s advanced airborne SAR system onboard DO228
No full textThe Microwaves and Radar Institute of the German Aerospace Center (DLR) is known for its consistent work on the field of airborne synthetic aperture radar and its application. In April 2008 we celebrate the 20th anniversary of the maiden flight of the well-known E-SAR system. E-SAR was maintained well over the time. It provided valuable knowledge to the science community, especially in the last 10 years. However, it became more and
more obvious that a technological renewal was inevitable. Consequently the development of a new SAR system was put on the line some years ago under the name ‘F-SAR’. F-SAR identifies the successor of the well-known ESAR system. The system is under development at the Microwaves and Radar Institute. The development was triggered by the demand for data being simultaneously acquired at different wavelengths and polarisations
as well as by the demand for very high range resolution
Publications et travaux du SAR : 1993
No full textCette bibliographie recense l'ensemble des travaux et publications réalisés par le CIRAD-SAR au cours de l'année 1993. Les principaux thèmes sont : conception des équipements et énergie, économie des systèmes ruraux, génie agronomique et mécanisation, génie et technologie agro-alimentaires, innovations dans les systèmes agricoles et agro-alimentaire
Denoising of SAR images
No full textMatter of discussion in this Ph. D. thesis is SAR (Synthetic Aperture Radar) image denoising.
Main elements of innovation are the introduction of SAR-BM3D, a denoising algorithm optimized for SAR data, and the introduction of a benchmark which enables the objective performance comparison of SAR denoising algorithms on simulated canonical SAR images.
In the first part of the thesis, basic concepts on SAR images are introduced, with special emphasis on its peculiar multiplicative noise, called speckle. A description of key ideas and tools of denoising techniques known in literature then follows.
After introducing the basic elements of SAR data processing, the main statistical features of SAR images are described, and it is clarified in which context the denoising techniques operate. Techniques are then classified as those that follow the homomorphic approach, where the multiplicative noise is turned into additive noise through a logarithmic transform, and those that take explicitly into account the multiplicative nature of noise. Afterwards, it is described how the introduction of the wavelet transform has brought new ideas into SAR image denoising and how the non-local filtering strategy, originally proposed in the AWGN field, has provided relevant results also in the application to SAR.
In this context, the novel SAR-BM3D algorithm is introduced which, starting from key elements of wavelet-based and non-local filtering implemented in BM3D, optimizes the elaboration for SAR data, following a non-homomorphic approach. A very detailed experimental analysis on simulated SAR images, obtained as optical images corrupted by artificial speckle, has been performed: results proved the SAR-BM3D algorithm to outperform traditional approaches, both in terms of PSNR and visual inspection.
Due to the well-known difficulties of evaluating the performance of denoising techniques on real SAR images, a workaround has been proposed. Rather than resorting to images corrupted by artificial speckle, a physical SAR simulator, SARAS (developed by the remote-sensing group of the Federico II University of Naples) has been used to generate a set of canonical benchmark SAR scenes. The main advantage of SARAS images is the availability of both the noisy and clean versions of the images, the latter acting as a reference to objectively evaluate the performances of different algorithms. We have shown in detail the procedure which leads to a definition of an objective criterion to compare results provided by different algorithms when working on real SAR images. For this purpose, different test cases have been selected and specific measures, suitable for the various scenes have been proposed for the characterization.
At the end of the thesis, open issues are pointed out and future research is outlined
Publications et travaux du SAR : 1995
No full textCette bibliographie recense l'ensemble des travaux et publications réalisés par le CIRAD-SAR au cours de l'année 1995. Les principaux thèmes sont : conception des équipements et énergie, économie des systèmes ruraux, génie agronomique et mécanisation, génie et technologie agro-alimentaires, innovations dans les sytèmes agricoles et agro-alimentaire
F-SAR – DLR’s New Multifrequency Polarimetric Airborne SAR
No full textF-SAR identifies the successor of the well-known E-SAR system. The system is under development at the Microwaves and Radar Institute. The development was triggered by the demand for data being simultaneously acquired at different wavelengths and polarisations as well as by the demand for very high range resolution
Fractal Models for SAR images
No full textIn this thesis the modeling of SAR (Synthetic Aperture Radar) images of natural surfaces described via fractal models is dealt with. A complete theoretical forward model linking the parameters describing the scene observed by the sensor to the stochastic characterization of the relevant SAR image is provided. The inverse problem is treated as well: a SAR image post-processing able to automatically retrieve - operating on an amplitude single SAR image - the fractal parameters of the scene, is presented.
The developed imaging model is based on sound geometrical and electromagnetic models that are combined according to the SAR impulse response function. The power spectral densities of appropriate cuts of the SAR image are evaluated in closed form in terms of the surface fractal parameters. The theoretical results are here conceptually assessed, analytically derived, graphically validated and numerically verified.
Moreover, based on the inversion of the forward theoretical model, an innovative SAR image post-processing for the fractal parameters estimation is implemented. It is firstly tested on simulated SAR images, then it is applied to different types of new generation (i.e. high resolution) SAR images. The generated fractal maps show themselves to be very useful for a wide range of application, e.g. prevention and monitoring of environmental disasters, geodynamic processes interpretation, land classification, rural planning, and so on
Digital Beamforming and MIMO SAR: Review and New Concepts
No full textSpaceborne Synthetic Aperture Radar (SAR) is a unique tool for large scale Earth observation, but the current generation of SAR sensors suffers from some fundamental limitations with regard to their imaging and mapping capabilities. To overcome these limitations, several new instrument architectures and SAR imaging modes have been suggested that employ digital beamforming (DBF), multiple aperture data recording and MIMO SAR tech-niques. This paper provides a critical review of these techniques and makes some suggestions for further im-provements. Special attention is given to advanced DBF and MIMO SAR concepts for ultra-wide swath imaging
Publications et travaux du SAR, janvier 1992 - juin 1994
No full textCette bibliographie recense l'ensemble des travaux et publications réalisés par le CIRAD-SAR depuis sa création (1992) jusqu'en juin 1994 et reçus au service de documentation. Les principaux thèmes sont : conception des équipements et énergie, économie des systèmes ruraux, génie agronomique et mécanisation, génie et technologie agro-alimentaire, innovations dans les systèmes agricoles et agro-alimentaire
Recent Developments and Applications of Multi-Pass Airborne Interferometric SAR using the E-SAR System
Get PDFAirborne SAR systems are traditionally considered to be a suitable testbed for the demonstration of new Earth observation
data acquisition techniques and for the development of new applications based on the acquired multi parameter data sets.
Spaceborne SAR system concepts and mission design is based on the experience gathered from these airborne SAR
experiments and from dedicated campaigns. DLR's E-SAR system is supporting these activities since the late 1980-ties
by providing high resolution multi-frequency and multi-polarisation data sets to a large user community. Triggered by the
scientific needs and also by the recent advancements in motion compensation techniques several new operating modes are
now available for the E-SAR system on a quasi-operational basis. This paper gives an overview of these techniques and
presents novel application examples
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