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  • Perturbation analysis of eigenvector-based target decomposition theorems in radar polarimetry

     López Martínez, Carlos; Alonso González, Alberto; Fabregas Canovas, Francisco Javier
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2014
    Journal article

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    A novel analysis of the statistics of the eigendecomposition of the coherency matrix and the H/A/a¯ parameters of polarimetric synthetic aperture radar data is addressed. The objective is to overcome previous approaches that prevented the extraction of information about the sample eigenvectors or restricted the analysis to simulated data. This paper considers a perturbation analysis of the eigendecomposition of the coherency matrix, making it possible to obtain analytical expressions for the sample eigenvalues and their means and variances, the sample mean entropy and anisotropy, the sample eigenvectors and the sample ai angles, as well as for the sample mean alpha angle a¯. All the parameters are shown to be estimated asymptotically non-biased with respect to the number of averaged samples. It is also demonstrated that the sample eigenvectors are more robust than the sample eigenvalues to the presence of speckle. Finally, a simple technique for the precise removal of the entropy bias is presented.

  • Wetland inundation monitoring by the synergistic use of ENVISAT/ASAR imagery and ancilliary spatial data

     Marti Cardona, Belen; Dolz Ripolles, Jose; López Martínez, Carlos
    Remote sensing of environment
    Date of publication: 2013
    Journal article

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    Wetlands are among the most ecologically important ecosystems on Earth and their sustainability depends critically on the water resources. In a scenario of climate change and increased anthropogenic pressure, detailed monitoring of the water resources provides a fundamental tool to assess the ecosystem health and identify potential threats. Doñana wetlands, in Southwest Spain, dry out every summer and progressively flood in fall and winter to a maximum extent of 30,000 ha. The wetland filling up process was monitored in detail during the 2006¿2007 hydrologic cycle by means of twenty-one Envisat/ASAR scenes, acquired at different incidence angles in order to maximize the observation frequency. Flood mapping from the two uncorrelated ASAR channel data alone was proved unfeasible due to the complex casuistic of Doñana cover backscattering. This study addresses the synergistic utilization of the ASAR data together with Doñana's digital elevation model and vegetation map in order to achieve flood mapping. Filtering and clustering algorithms were developed for the automated generation of Doñana flood maps from the ASAR images. The use of irregular filtering neighborhoods adapted to the elevation contours drastically improved the ASAR image filtering. Edge preservation was excellent, since natural edges closely follow terrain contours. Isotropic neighborhoods were assumed of a single class and their intensities were averaged. As a result, intensity fluctuations due to speckle and texture over areas of the same cover type were smoothed remarkably. ..

    on the water resources. In a scenario of climate change and increased anthropogenic pressure, detailedmonitoring of the water resources provides a fundamental tool to assess the ecosystem health and identify potential threats. Doñana wetlands, in Southwest Spain, dry out every summer and progressively flood in fall and winter to a maximum extent of 30,000 ha. Thewetland filling up processwasmonitored in detail during the 2006–2007 hydrologic cycle bymeans of twenty-one Envisat/ASAR scenes, acquired at different incidence angles in order to maximize the observation frequency. Flood mapping from the two uncorrelated ASAR channel data alone was proved unfeasible due to the complex casuistic of Doñana cover backscattering. This study addresses the synergistic utilization of the ASAR data together with Doñana's digital elevation model and vegetation map in order to achieve flood mapping. Filtering and clustering algorithms were developed for the automated generation of Doñana floodmaps from the ASAR images. The use of irregular filtering neighborhoods adapted to the elevation contours drastically improved the ASAR image filtering. Edge preservation was excellent, since natural edges closely follow terrain contours. Isotropic neighborhoodswere assumed of a single class and their intensitieswere averaged. As a result, intensity fluctuations due to speckle and texture over areas of the same cover type were smoothed remarkably. The clustering and classification algorithm operate on individual sub-basins, as the pixel elevation is more accurately related to the cover classes within them. Vegetation and elevation maps plus knowledge of Doñana backscattering characteristics from preceding studies were initially used to select seed pixelswith high confidence on their class membership. Next, a region growing algorithm extends the seed regions with new pixels based on their planimmetric adjacency and backscattering Mahalanobis distance to the seeds. During the seed region growth, new pixels' possible classes are not constrained to their cover type according to the vegetation map, so the algorithm is able to capture temporal changes in the vegetation spatial distribution. Comparison of the resultant classification and concurrent ground truth yielded 92% of flood mapping accuracy. The flood mapping method is applicable to the available ASAR images of Doñana fromsix other hydrologic cycles.

  • Bilateral distance based filtering for polarimetric SAR data

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean; Deng, Xinping
    Remote Sensing
    Date of publication: 2013-10-30
    Journal article

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    This paper introduces a non-linear Polarimetric SAR data filtering approach able to preserve the edges and small details of the data. It is based on exploiting the data locality in both, the spatial and the polarimetric domains, in order to avoid mixing heterogeneous samples of the data. A weighted average is performed over a given window favoring pixel values that are close on both domains. The filtering technique is based on a modified bilateral filtering, which is defined in terms of spatial and polarimetric distances. These distances encapsulate all the knowledge in both domains for an adaptation to the data structure. Finally, the proposed technique is employed to process a real RADARSAT-2 dataset.

  • PolSAR time series processing and analysis based on Binary Partition Trees

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2013-02-12
    Presentation of work at congresses

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  • A study of the RVoG coherent scattering model validity in PolInSAR for forests studies

     López Martínez, Carlos; Alonso González, Alberto
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    This work addresses the analysis of the validity of the Random-Volume-over-Ground scattering model for forests studies based on PolInSAR data. The analysis is based on the definition of a Generalized Likelihood Ratio Test that allows to test the model validity for all the pixels of the images and without any external information. Finally, the validity of the RVoG models assumption is tested for data from Tropical and Boreal forests imaged at P- and L-band at different interferometric configurations.

  • Study of the speckle noise effects over the eigen decomposition of polarimetric SAR data: a review

     López Martínez, Carlos; Alonso González, Alberto; Fabregas Canovas, Francisco Javier
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2013-01
    Presentation of work at congresses

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    This paper is focused on considering the effects of speckle noise on the eigen decomposition of the co- herency matrix. Based on a perturbation analysis of the matrix, it is possible to obtain an analytical expression for the mean value of the eigenvalues and the eigenvectors, as well as for the Entropy, the Anisotroopy and the dif- ferent a angles. The analytical expressions are compared against simulated polarimetric SAR data, demonstrating the correctness of the different expressions.

  • Phase quality optimisation techniques and limitations in polarimetric differential SAR interferometry

     Iglesias, Rubén; Monells Miralles, Daniel; Fabregas Canovas, Francisco Javier; Mallorqui Franquet, Jordi Joan; Aguasca Sole, Alberto; López Martínez, Carlos
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2013-01
    Presentation of work at congresses

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    In this paper, the application of polarimetric optimization techniques for Differential SAR Interferometry (DInSAR) applications is studied. The objective of the proposed techniques is to increase the number of temporal coherent scatterers, improving thus the robustness of the DInSAR algorithms exploiting the polarimetric capabilities of data. The relationship between optimum coherences or amplitude dispersion maps, depending on the pixels selection method used, and the final DInSAR results is analyzed, using both orbital and Ground-Based SAR fully-polarimetric data. Moreover, the main advantages and drawbacks of each optimization method will be analyzed, especially when polarimetric stability does not apply. With the optimization techniques presented up to a twofold increase of the pixel candidates in the coherence case and up to a factor of seven in the amplitude dispersion case may be reached.

  • Imágenes SAR para la cartografía de doñana: beneficios del filtrado asisistido por información espacial auxiliar

     Marti Cardona, Belen; Dolz Ripolles, Jose; López Martínez, Carlos
    Congreso Nacional de la Asociación Española de Teledetección
    Presentation's date: 2013-10
    Presentation of work at congresses

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  • A maximum likelihood analysis of the RVoG model for forestry studies in polarimetric SAR interferometry

     López Martínez, Carlos; Alonso González, Alberto
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2013-01
    Presentation of work at congresses

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    This work analyses the validity of the RVoG model as- sumption in case of PolInSAR data in forestry analy- sis. In order to assure that the interferometric coherence describes a line, as imposed by the RVoG model, the normalized PolInSAR coherency matrix must be affine equivalent to an Hermitian matrix. On the basis of this observation, two tests for the RVoG model hypothesis are proposed. A test based on the analysis of the coherence region shape, and a test based on a Maximum Likelihood approach, on the basis of the zero mean, complex, Gaus- sian distribution. Preliminary results would indicate a larger validity of the model at P-band over L-band and, in case of Tropical forests.

  • Statistical study of the H/A/Alpha decomposition based on a perturbation analysis of the coherency matrix

     López Martínez, Carlos; Alonso González, Alberto
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    The eigendecomposition of the coherency matrix, as well as the Entropy, Anisotropy and mean Alpha angle are crucial for the physical understanding of the scattered echo in SAR polarimetry. This contribution considers a perturbation analysis of the coherency matrix that allows the statistical characterization of all the previous parameters. In addition, a novel and effective algorithm for the unbiased estimation of the Entropy parameter is presented.

  • Imágenes SAR para la cartografía de Doñana: beneficios del filtrado asistido por información espacial auxiliar

     Marti Cardona, Belen; Dolz Ripolles, Jose; López Martínez, Carlos
    Congreso de la Asociación Española de Teledetección
    Presentation's date: 2013-10-23
    Presentation of work at congresses

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  • Monitoring and study of mountainous regions in the Pyrenees area based on polarimetric RADARSAT-2 Data

     Zhan, Yu; López Martínez, Carlos; Alonso González, Alberto; Reppucci, Antonio; Caparrini, Marco
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2013-01
    Presentation of work at congresses

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    drological applications. Information about spatial and temporal variability of snow parameters is needed for the modeling and forecasting of snow involved phenomena such as melt runoff, avalanche prediction and water resources forecasting. Active microwave remote sensing represents a valuable tool in the enhancement of snow monitoring providing appropriate spatial and temporal resolution and almost independence of weather conditions due to penetration capabilities of microwave radiation. This contribution represents the result of the research work conducted in the frame of the still on-going EOSWAN project, targeting the study of the feasibility of snow monitoring with Cband PolSAR data over mountainous regions in the Pyrenees area, North-Eastern Spain.

  • Cancellation of scattering mechanisms in PolInSAR: application to underlying topography estimation

     López Martínez, Carlos; Papathanassiou, Kostantinos
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-02
    Journal article

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    This paper investigates the polarimetric dependence of the interferometric complex correlation and proposes amethodology for cancelling individual scattering mechanisms, in terms of the complex correlation coefficient phase, under the assumption of the random volume over ground model. This allows the estimation of the ground topography on forested and vegetated areas. The first part of the analysis considers the separation of the volume from the ground (including the double-bounce scattering mechanism). This process identifies the polarization states, without constraining them to be equal in both polarimetric acquisitions, which allow to cancel either the volume scattering contribution or the ground contribution. In order to have access to the interferometric phase of the remaining or isolated scattering mechanism, the polarimetric phase contribution of this scattering mechanism has to be removed in a second step. In the case of forested areas, the previous methodology is considered from two different point of views. For the estimation of the underlying ground topography, the cancellation of the volume scattering contribution makes possible to access the interferometric phase associated to the ground contribution. In addition, the interferometric information associated to the volume scattering contribution is estimated based on the cancellation of the ground contribution. The proposed techniques are analyzed on the basis of simulated and experimental polarimetric interferometric synthetic aperture radar data, demonstrating that the ground topography, as well as the height associated to the volume contribution, are asymptotically nonbiased and dependent on the shape of the particles of the random volume. In case of spheres (η = 0), the ground-to-volume ratio presents large values favoring the accurate estimation of the topographic phase. For the case of dipole like particles (η = 0.5), the ground-to-volume ration decreases producing a coherence |ρ| in the order of 0.1, making necessary a large speckle filtering to obtain a reliable estimation of the topographic phase.

  • Polarimetric temporal analysis of urban environments with a ground-based SAR

     Pipia, Luca; Fabregas Canovas, Francisco Javier; Aguasca Sole, Alberto; López Martínez, Carlos
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-04
    Journal article

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    Revisiting time constitutes a key constraint for continuous monitoring activities based on space- and airborne synthetic aperture radar (SAR) acquisitions. Conversely, the employment of terrestrial platforms overcomes this limitation and makes it possible to perform time-continuous observations of small space-scale phenomena. New research lines of SAR dealing with the backscattering evolution of different types of scenarios become hence possible through the analysis of ground-based SAR (gbSAR) data collections. The Remote Sensing Laboratory of the Universitat Politècnica de Catalunya drove a one-year measurements campaign in the village of Sallent, northeastern Spain, using its X-Band gbSAR sensor. The field experiment aimed at studying the subsidence phenomenon induced by the salt mining activity carried out in this area during the past decades. In this paper, the polarimetric behavior of an urban environment is investigated at different time scales. After a brief description of the test site and the measurement campaign, the analysis is focused on the stability on man-made structures at different time scales. PolSAR data monthly acquired from June 2006 to July 2007 are employed to stress the presence of nonstationary backscattering processes within the urban scene and the effect they have on differential phase information. Then, a filtering procedure aiming at reducing backscattering randomness in one-day and long-term data collections is then put forward. The improvements provided by the proposed technique are assessed using a new polarimetric descriptor, the time entropy. In the end, the importance of preserving the interferometric phase information from nonstationary backscattering contaminations using fully polarimetric data is discussed.

    Revisiting time constitutes a key constraint for continuous monitoring activities based on space- and airborne synthetic aperture radar (SAR) acquisitions. Conversely, the employment of terrestrial platforms overcomes this limitation and makes it possible to perform time-continuous observations of small space-scale phenomena. New research lines of SAR dealing with the backscattering evolution of different types of scenarios become hence possible through the analysis of ground-based SAR (gbSAR) data collections. The Remote Sensing Laboratory of the Universitat Politècnica de Catalunya drove a one-year measurements campaign in the village of Sallent, northeastern Spain, using its X-Band gbSAR sensor. The field experiment aimed at studying the subsidence phenomenon induced by the salt mining activity carried out in this area during the past decades. In this paper, the polarimetric behavior of an urban environment is investigated at different time scales. After a brief description of the test site and the measurement campaign, the analysis is focused on the stability on man-made structures at different time scales. PolSAR data monthly acquired from June 2006 to July 2007 are employed to stress the presence of nonstationary backscattering processes within the urban scene and the effect they have on differential phase information. Then, a filtering procedure aiming at reducing backscattering randomness in one-day and long-term data collections is then put forward. The improvements provided by the proposed technique are assessed using a new polarimetric descriptor, the time entropy. In the end, the importance of preserving the interferometric phase information from nonstationary backscattering contaminations using fully polarimetric data is discussed

  • 2013 IEEE GRSS Gold Early Career Award

     López Martínez, Carlos
    Award or recognition

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  • Polsar time series temporal change detection and analysis with binary partition trees

     Alonso González, Alberto; López Martínez, Carlos
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    In this paper the exploitation of PolSAR temporal series datasets is presentedin the context of change detection and characterization. A Binary Partition Tree (BPT) data structure is employed in order to extract homogeneous regions of the image containing pixels that are following a similar polarimetric temporal evolution. Then the temporal dimension of the data is analyzed firstly to quantify the significance of the polarimetric temporal variation, making possible the detection of scene changes, and secondly to analyze and characterize those changes. Finally, the proposed technique is employed to process a real RADARSAT-2 dataset to show its capabilities and potentialities.

  • Statistical study of the H/A/a decomposition based on a perturbation analysis of the coherency matrix

     López Martínez, Carlos; Alonso Gonzalez, Alberto
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    The eigendecomposition of the coherency matrix, as well as the Entropy, Anisotropy and mean Alpha angle are crucial for the physical understanding of the scattered echo in SAR polarimetry. This contribution considers a perturbation analysis of the coherency matrix that allows the statistical characterization of all the previous parameters. In addition, a novel and effective algorithm for the unbiased estimation of the Entropy parameter is presented.

  • Advanced polarimetric optimization for DInSAR applications with Ground-Based SAR

     Iglesias, Rubén; Fabregas Canovas, Francisco Javier; Aguasca Sole, Alberto; López Martínez, Carlos; Alonso Gonzalez, Alberto
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2012-04
    Presentation of work at congresses

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    In this paper, the applications of advanced polarimetric optimization techniques for Differential Interferometric SAR (DInSAR) pixel selection are explored in the framework of deformation map retrieval in landslides. Unfortunately, most of high mountain landslides occur on vegetated areas with a poor density of coherent scatterers that with a fast decorrelation at X-band. The objective of the techniques proposed in this paper is to increase the number of pixels with good quality, and thus the robustness of DInSAR algorithms, by exploiting the larger density of coherent scatterers present in polarimetric SAR data. Using Ground-Based SAR zero-baseline fullypolarimetric data sets, the relationship between optimum coherences and its corresponding phase in terms of DInSAR application is carefully analyzed. In the paper, different coherence optimization methods available in the literature are studied. The main advantages and drawbacks of the different approaches are drawn.

  • Application of high resolution spotlight TerraSAR-X data to landslide monitoring

     Iglesias, Rubén; Monells Miralles, Daniel; Centolanza, Giuseppe; Mallorqui Franquet, Jordi Joan; Fabregas Canovas, Francisco Javier; Aguasca Sole, Alberto; López Martínez, Carlos
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2012-04
    Presentation of work at congresses

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    This paper seeks to demonstrate that radar-based remote sensing techniques, especially those based on orbital sensors, can be as effective as the conventional geotechnical and discrete GPS measurement ones for the detection and monitoring of well suited landslides. Unfortunately, deformation can only be retrieved for those landslides presenting a good orientation with respect the satellite orbit. In addition, many of the high mountain landslides are vegetated areas that decorrelate faster at X-band. As in these scenarios the number of persistent scatterers can be low and, at the same time, the area of interest is usually small, the processing can be benefited of the usage of high-resolution data that will maximize the chances of detecting persistent scatters coming from both natural targets and man-made structures. The high resolution Spotlight mode of TerraSAR-X is thus the perfect choice as it offers a fine resolution. In addition, its 11 days of revisit time and X-band carrier allows the monitoring of small variations in the landslide trend and deal with its variable dynamics. The landslide of study is ‘El Forn de Canillo’ (Andorra) where the deformation results will be compared and validated with those obtained with the deployed UPC’s Ground-Based (GB-SAR) X-band sensor.

  • An evaluation of PolSAR speckle filters on Compact-Pol images

     Foucher, Samuel; Landry, Tom; López Martínez, Carlos; Charbonneau, François; Gagnon, Langis
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    The goal of this study is to evaluate some polarimetric speckle filters when applied to Compact Polarimetry (CP) data. Seven filters are evaluated on a set of artificial CP images. Performances regarding image restoration and polarimetric information preservation are evaluated.

  • The polarimetric ratio filter applied to PolInSar images

     Foucher, Samuel; López Martínez, Carlos; Charbonneau, François
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    We are proposing recursive filter for the filtering of Single Look Complex PolInSAR data. This recursive filter allows the iterative refinement of a coarse multilook estimate by reintroducing details that have been oversmoothed. We investigate if wether or not information about the image structure (i.e. spatial details) could be recovered from all the terms of the PolInSAR matrix. Preliminary results on simulated images show also that bias on various polarimetric parameters are decreasing with iterations.

  • Access to the full text
    Local texture stationarity indicator for filtering Doñana wetlands SAR images  Open access

     Marti Cardona, Belen; López Martínez, Carlos; Dolz Ripolles, Jose
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    This paper defines a new operator, named Ds, for local texture stationarity assessment on SAR images. . The aim is to discriminate heterogeneous targets from land cover types of high normalized variance values, as those observed in flooded vegetation areas of Doñana wetlands. Suitable Ds thresholds for such discrimination were estimated for different window sizes through Monte Carlo simulations of synthetic textures. Maximum stationary texture windows were then determined on Doñana ASAR scenes by Ds multi-resolution thresholding and averaging was applied within. Results reveal the substantial degree of smoothing achieved over high variance cover types, while edges among different targets were properly preserved.

  • Phase quality optimization in Orbital Differential SAR Interferometry with fully polarimetric data

     Monells Miralles, Daniel; Iglesias, Ruben; Mallorqui Franquet, Jordi Joan; Fabregas Canovas, Francisco Javier; López Martínez, Carlos
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    Orbital Differential SAR Interferometry (DInSAR) is a well-known technique to retrieve terrain deformation phenomena from wide areas with high resolution. Historically its application has been limited to single polarization SAR, mainly due to the unavailability of polarimetric data. Lately, the launch of several satellites with polarimetric capabilities, such as Radarsat-2 or TerraSAR-X, allows merging polarimetric and interferometric techniques in order to improve the results obtained in the DInSAR processing. This work will explore the existent analytical techniques in order to optimize the quality of the subsidence results. The dataset used contains 35 Fine Quad-Pol Radarsat-2 acquisitions over the city of Barcelona (Spain).

  • Space-Time PolSAR data temporal series processing based on binary partition trees

     Alonso Gonzalez, Alberto; López Martínez, Carlos
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2012-04
    Presentation of work at congresses

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    A processing technique to exploit temporal series of coregistered Polarimetric Synthetic Aperture Radar (PolSAR) images is presented in this paper. This technique will be based on a region-based and multi-scale data representation, the Binary Partition Tree (BPT). The BPT represents the data structure at different detail levels and may be useful for different applications. Different alternatives to deal with the temporal dimension of the data will be addressed and analyzed over a real RADARSAT-2 dataset.

    First Place Student Paper Award, 9th European Conference on Synthetic Aperture Radar

  • Estimation of snow pack characteristics by means of polarimetric SAR data

     Reppucci, Antonio; Banque, Xavier; López Martínez, Carlos; Zhan, Yu; Alonso Gonzalez, Alberto
    SPIE International Symposium - Remote Sensing Europe
    Presentation's date: 2012-10
    Presentation of work at congresses

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    Characterization of the snow-pack is fundamental for several applications in hydrology, such as modelling and forecasting of snow melt runoff, water resource management and risk analysis. Thanks to its night/day capabilities and weather conditions independence, Synthetic Aperture Radar (SAR) represents a valuable tool for snow monitoring, especially in mountain areas often covered by clouds. The goal of the research project presented in this communication is to investigate the sensitivity of fully polarimetric Cband satellite SAR data to different conditions of the snow-pack. The work is based on the use of RADARSAT-2 C-band SAR data and collocated in-situ measurements acquired during two ground campaigns over an area located in the Catalan Pyrenees, that took place between February to October 2011. The main outcome of this study is the definition of two new polarimetric parameters sensitive to the snow presence, able to distinguish between dry-snow and non snow cover, allowing a qualitative remote sensing with C-band polarimetric space-borne SAR data. The importance of developing an application based on remote sensed data will be discussed. Results of the activity scheduled during the first year of the project will be highlighted. Observed deviations between SAR measurements and in situ measurement shall be analyzed and discussed.

  • Analysis and validity of the polInSAR line model on forested areas

     López Martínez, Carlos; Fabregas Canovas, Francisco Javier; Alonso Gonzalez, Alberto
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2012-04
    Presentation of work at congresses

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    This paper focuses on the analysis of certain hypotheses considered in quantitative remote sensing of forest areas by means of Polarimetric SAR Interferometry (PolInSAR). When addressing the quantitative estimation of forest parameters in PolInSAR, the estimation is usually based on the inversion of the Random Volume over Ground (RVoG) coherent scattering model. We present an study of the validity of this assumption, based on the analysis of the measured data and the coherence region resulting from the variation of the interferometric coherence as a function of polarization.

  • Polarimetric optimization for DInSAR pixel selection with ground-based SAR

     Iglesias, Rubén; Fabregas Canovas, Francisco Javier; Aguasca Sole, Alberto; López Martínez, Carlos; Alonso Gonzalez, Alberto; Mallorqui Franquet, Jordi Joan
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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  • Variable local weight filtering for PolSAR data speckle noise reduction

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    This paper presents a Polarimetric SAR data speckle filtering technique, based on a combined filtering in the spatial and polarimetric domains. It is based on a bilateral filtering employing distance measures over these domains. These measures concentrate all the information related to the domain structure that is needed for an adaptation to the scene morphology. A weighted average is performed over a given window favoring closer and similar pixels. As a consequence, an adaptive filtering is achieved, attaining higher filtering over homogeneous areas whereas point scatters remain almost unchanged. Results will be shown over a real RADARSAT-2 data.

  • Temporal PolSAR image series exploitation with binary partition trees

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    In this paper, the processing of temporal PolSAR image series is addressed through a region-based and multi-scale data representation, the Binary Partition Tree (BPT). This structure contains useful information related to the data structure at different detail levels that may be employed for different applications. The construction of this structure ans its exploitation is addressed in this work in the context of the speckle filtering and data segmentation applications. A new region model and processing strategy are defined to tackle with the temporal dimension of the data. Finally, to illustrate the capabilities of the proposed technique, results are shown with a real RADARSAT-2 dataset.

  • Processing multidimensional SAR and hyperspectral images with binary partition tree

     Alonso Gonzalez, Alberto; Valero, Silvia; Chanussot, Jocelyn; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    Proceedings of the IEEE
    Date of publication: 2012-08-13
    Journal article

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    The current increase of spatial as well as spectral resolutions of modern remote sensing sensors represents a real opportunity for many prac tical applications but also generates important challenges in terms of image processing. In particular, the spatial correlation between pixels and/or the spectral correlation between spectral bands of a given pixel cannot be ignored. The traditional pixel-based representation of images does not facilitate the handling of these correlations. In this paper, we discuss the inter est of a particular hierarchical region-based representation of images based on binary partition tree (BPT). This representation approach is very flexible as it can be applied to any type of image. Here both optical and radar images will be discussed. Moreover, once the image representation is computed, it can be used for many different applications. Filtering, segmentation, and classifica- tion will be detailed in this paper. In all cases, the interest of the BPT representation over the classical pixel-based representa- tion will be highlighted

  • Improving Wishart Classification of Polarimetric SAR Data Using the Hopfield Neural Network Optimization Approach

     Pajares Martinsanz, Gonzalo; López Martínez, Carlos; Sánchez Lladó, Francisco Javier; Molina, Iñigo
    Remote Sensing
    Date of publication: 2012-11-19
    Journal article

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  • 9th European Conference on Synthetic Aperture Radar Student Paper Award

     Alonso Gonzalez, Alberto; López Martínez, Carlos
    Award or recognition

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  • SAR Multidimensional para la observación de la tierra: sistemas, procesado y aplicaciones

     Alonso Gonzalez, Alberto; Centolanza, Giuseppe; Monells Miralles, Daniel; López Martínez, Carlos; Mallorqui Franquet, Jordi Joan; Broquetas Ibars, Antoni; Fabregas Canovas, Francisco Javier; Makhoul Varona, Eduardo; Aguasca Sole, Alberto
    Participation in a competitive project

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  • Filtering and segmentation of polarimetric SAR data based on binary partition trees

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2012-02
    Journal article

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    In this paper,we propose the use of binary partition trees (BPT) to introduce a novel region-based and multi-scale polarimetric SAR (PolSAR) data representation. The BPT structure represents homogeneous regions in the data at different detail levels. The construction process of the BPT is based, firstly, on a region model able to represent the homogeneous areas, and, secondly, on a dissimilarity measure in order to identify similar areas and define the merging sequence. Depending on the final application, a BPT pruning strategy needs to be introduced. In this paper, we focus on the application of BPT PolSAR data representation for speckle noise filtering and data segmentation on the basis of the Gaussian hypothesis, where the average covariance or coherency matrices are considered as a region model. We introduce and quantitatively analyze different dissimilarity measures. In this case, and with the objective to be sensitive to the complete polarimetric information under the Gaussian hypothesis, dissimilarity measures considering the complete covariance or coherency matrices are employed.When confronted to PolSAR speckle filtering, two pruning strategies are detailed and evaluated. As presented, the BPT PolSAR speckle filter defined filters data according to the complete polarimetric information. As shown, this novel filtering approach is able to achieve very strong filtering while preserving the spatial resolution and the polarimetric information. Finally, the BPT representation structure is employed for high spatial resolution image segmentation applied to coastline detection. The analyses detailed in this work are based on simulated, as well as on real PolSAR data acquired by the ESAR system of DLR and the RADARSAT-2 system.

  • Binary partition tree as a polarimetric SAR data representation in the space-time domain

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    The aim of this paper is to present a Polarimetric Synthetic Aperture Radar data processing technique on the space-time domain. This approach is based on a Binary Partition Tree (BPT), which is a region-based and multi-scale data representation. Results with series of RADARSAT-2 real data are analyzed from the point of view of speckle filtering and change detection applications, to illustrate the capabilities to detect and preserve spatial and temporal contours.

  • Analysis of volumetric scatters based on TanDEM-X polarimetric interferometric SAR data

     López Martínez, Carlos; Alonso Gonzalez, Alberto; Fabregas Canovas, Francisco Javier; Papathanassiou, Kostantinos
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    Polarimetric SAR Interferometry makes possible a detailed analysis of the volumetric scattering processes present in microwave scattering in case of forest areas. In previous contributions, the authors, under the hypothesis of the RVoG coherent scattering model, developed a process for the direct extraction of the ground topography. In this paper, the authors present a generalization of this technique allowing to determine a set of scattering mechanisms making possible an optimization process for the estimation of the ground topography. The applicability of this technique, in case of X-band polarimetric SAR interferometric data, is explored considering data obtained in the frame of the TanDEM-X mission.

  • Underlying topography estimation and separation of scattering contributions over forests based on polInSAR data

     López Martínez, Carlos; Alonso Gonzalez, Alberto; Fabregas Canovas, Francisco Javier; Papathanassiou, Kostantinos
    Advances in the Science and Applications of SAR Interferometry
    Presentation's date: 2011-09-20
    Presentation of work at congresses

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    The work detailed in this paper analyzes the topographic phase retrieval process on forested areas by means of Polarimetric Interferometric SAR data. On the basis of the Random Volume over Ground scattering model, an alternative implementation for the retrieval of the topographic phase, avoiding the bias introduced by the volumetric scattering components is presented.

  • Application of polarimetric techniques in DinSAR processing for space borne subsidence monitoring

     Monells Miralles, Daniel; Mallorqui Franquet, Jordi Joan; Centolanza, Giuseppe; López Martínez, Carlos
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • Temporal and incidence angle dependency of PolSAR data for agricultural land cover analysis and characterization

     Montero, Ismael; López Martínez, Carlos; Fabregas Canovas, Francisco Javier
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • Influence of speckle filtering of polarimetric SAR data on different classification methods

     Fang, Cao; Deladalle, Charles-Alban; Nicolas, Jean-Marie; Tupin, Florence; Denis, Loic; Ferro-Famil, Laurent; Pottier, Eric; López Martínez, Carlos
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    This paper analyzes the effects of speckle filtering on polarimetric SAR decomposition and classification. We compared the results of the refined Lee, IDAN and Non-Local Polarimetric filters, and discussed their ALOS/PALSAR and RadarSat–2 polarimetric SAR data are used for illustration.

  • Separation of scattering contributions in Polarimetric SAR Interferometry

     López Martínez, Carlos; Papathanassiou, Kostantinos; Fabregas Canovas, Francisco Javier; Alonso Gonzalez, Alberto
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • PolSAR speckle filtering and segmentation based on binary partition tree representation

     Alonso Gonzalez, Alberto; López Martínez, Carlos; Salembier Clairon, Philippe Jean
    International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • Forest parameter estimation in the Pol-InSAR context employing the multiplicative¿additive speckle noise model

     López Martínez, Carlos; Fabregas Canovas, Francisco Javier; Pipia, Luca
    ISPRS journal of photogrammetry and remote sensing
    Date of publication: 2011-09
    Journal article

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    This paper addresses the problem of speckle noise on single baseline polarimetric SAR interferometry (Pol-InSAR) on the basis of the multiplicative–additive speckle noise model. Considering this speckle noise model, a novel filtering technique is defined and studied in terms of simulated and experimental Pol-InSAR data. As demonstrated, the use of the multiplicative–additive speckle noise model does not lead to a corruption of the useful information but to an improvement of its estimation. The performance of the algorithm is analyzed in terms of the physical parameters retrieved from the filtered data, that in this work correspond to the forest height and the ground phase. In case of experimental data, the retrieved forest height is compared and validated against Lidar ground truth measurements.

  • Transpolarizing trihedral corner reflector characterization using a GB-SAR system

     Ferrer, Pere J.; López Martínez, Carlos; Aguasca Sole, Alberto; Pipia, Luca; González Arbesú, José María; Fabregas Canovas, Francisco Javier; Romeu Robert, Jordi
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2011-07
    Journal article

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    The use of a low-profile, lightweight, and easy-to-fabricate transpolarizing surface placed on one side of a trihedral corner reflector (TCR) as a polarimetric calibrator is presented in this letter. The transpolarizing TCR presents a high backscattered cross-polar response contrary to standard TCRs. The performance of this device has been tested at the X-band using the Universitat Politecnica de Catalunya ground-based synthetic aperture radar.

  • Improving the wishart synthetic aperture radar image classifications through deterministic simulated annealing

     Sánchez Lladó, Francisco Javier; Pajares Martinsanz, Gonzalo; López Martínez, Carlos
    ISPRS journal of photogrammetry and remote sensing
    Date of publication: 2011-11
    Journal article

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    This paper proposes the use of Deterministic Simulated Annealing (DSA) for Synthetic Aperture Radar (SAR) image classification for cluster refinement. We use the initial classification provided by the maximum- likelihood classifier based on the complex Wishart distribution that is then supplied to the DSA optimization approach. The goal is to improve the classification results obtained by the Wishart approach. The improvement is verified by computing a cluster separability coefficient. During the DSA optimization process, for each iteration and for each pixel, two consistency coefficients are computed taking into account two kinds of relations between the pixel under consideration and its neighbors. Based on these coefficients and on the information coming from the pixel itself, it is re-classified. Several experiments are carried out to verify that the proposed approach outperforms the Wishart strategy. We try to improve the classification results by considering the spatial influences received by a pixel through its neighbors. Finally, a link about the contribution of DSA to thematic mapping is also established.

  • Fuzzy cognitive maps applied to synthetic aperture radar image classifications

     Pajares Martinsanz, Gonzalo; Sánchez Lladó, Francisco Javier; López Martínez, Carlos
    Date of publication: 2011-08-08
    Book chapter

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    This paper proposes a method based on Fuzzy Cognitive Maps (FCM) for improving the classification provided by the Wishart maximum-likelihood based approach in Synthetic Aperture Radar (SAR) images. FCM receives the classification results provided by the Wishart approach and creates a network of nodes associating a pixel to a node. The activation levels of these nodes define the degree of membeship of each pixel to each class. These activations levels are iteratively reinforced or punished based on the existing relations among each node and its neighbours and also taking into account the own node under consideration. Through a quality coefficient we measure the performance of the proposed approach with respect to the Wishart classifier.

  • HYPERSPECTRAL IMAGE REPRESENTATION AND PROCESSING USING BINARY PARTITION TREES

     Valero Valbuena, Silvia
    Defense's date: 2011-12-09
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Clasificación de imágenes POLSAR mediante enfriamiento simulado: Una mejora del clasificador wishart

     Sánchez Lladó, Francisco Javier
    Defense's date: 2011-03-10
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Post-processing methods for ocean monitoring in sar images  Open access  awarded activity

     Tello Alonso, Marivi
    Defense's date: 2011-02-07
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    In the recent years, a wide interest has been focused on research and development for the operational use of satellite remote sensing tools for Earth observation. Among different types of sensors, Synthetic Aperture Radars (SAR) offer distinctive characteristics, essential for several applications. The observation capability of SAR sensors is independent of the day – night cycle, of the presence of clouds and of the weather conditions in general. Nevertheless, due to the processing involved in the synthesis of SAR images, automatic interpretation of SAR data is awkward. For an extended operational exploitation of SAR products, the development of specific unsupervised techniques for the post-processing of SAR images is necessary. After analyzing the particularities of SAR images, focusing in particular on the elements making their interpretation difficult, this dissertation proposes a set of post-processing techniques for oceanic SAR images, based on time – frequency methods and in particular on the wavelet theory. First, a multiscale algorithm for automatic spot detection in a noisy background has been developed. It is based on the pointwise combination of wavelet coefficients of different bands at the same scale. This technique has been applied to automatic vessel detection and, more specifically, to difficult situations of detection: small fishing ships with low reflectivity. Its efficiency has been compared to other existing algorithms. After that, a method based on the pointwise combination of wavelet subbands at different scales has been proposed. It has been applied to the robust detection of frontiers and linear features. This technique has been employed for the unsupervised detection and monitoring of the coastline in SAR images. Its robustness has been proven through test on a large set of images showing diverse characteristics. Then, the issue of texture analysis in oceanic SAR images has been addressed. An algorithm for the estimation of the local regularity has been proposed, based on the quantification of the wavelet spectrum evolution through scales. A measure of the local fractality is derived from the local regularity. This technique is applied to the detection of oil spills in the ocean surface in SAR satellite based images. The contributions of this dissertation range in two directions. On the one hand, in the direction of multiscale signal processing and, on the other hand, in the direction of automatic interpretation of SAR images. For the multiscale signal processing, a different way of understanding and applying time – scale decompositions (or, equivalently, time - frequency) is proposed. In order to take more efficiently into account the information content in the projected space, the methods proposed carry out the analysis directly in the transformed domain. For the unsupervised interpretation of SAR images, the suitability of the multiscale framework has been justified. Inscribed in this multiscale theory, the novel techniques proposed in this dissertation are simple, flexible, robust and self-contained.

    En els darrers anys, la investigació per a la utilització operacional d’eines de teledetecció satel·litàries per a aplicacions d’observació de la Terra s’està desenvolupant ràpidament. Entre els diferents tipus de sensors satel·litaris existents, els radars d’obertura sintètica o SARs ofereixen unes característiques distintives, que els fan molt interessants per a diferents aplicacions. Tenen capacitat d’observació tant de dia com de nit i no es veuen afectats per la presència de núvols ni per condicions meteorològiques adverses. No obstant, degut al mètode d’adquisició de les imatges SAR, la seva interpretació automàtica és difícil. Per a una explotació operacional i estesa de les dades SAR, és necessari desenvolupar tècniques automàtiques i específiques de post-processament de les imatges SAR. Després d’analitzar les característiques de les imatges SAR que fan que el seu processament automàtic sigui difícil, aquesta tesi proposa un seguit de tècniques de post-processament per a imatges SAR oceàniques basades en mètodes temps – freqüència. En primer lloc, s’ha desenvolupat, mitjançant combinació punt a punt de bandes a una mateixa escala del domini wavelet, un algoritme multiescalar per a la detecció automàtica de spots en entorns sorollosos. Aquest mètode s’ha aplicat a la detecció automàtica de vaixells i, en particular, als casos difícils de detecció: vaixells petits i amb reflectivitat feble. El seu rendiment s’ha comparat amb algoritmes operacionals. En segon lloc, es proposa un mètode basat en la combinació punt a punt de bandes a diferents escales del domini wavelet, per a la detecció robusta de fronteres i línies. Aquesta tècnica s’ha provat per a la detecció automàtica i el seguiment de la línia de costa en imatges SAR. S’ha provat la seva robustesa. Per últim, s’ha plantejat el problema de l’anàlisi de textures a les imatges SAR oceàniques. S’ha proposat un algoritme per a l’estimació de la regularitat local, basat en la quantificació de l’evolució de l’espectre wavelet a través de les escales. A través de la regularitat local, es deriva una mesura de la fractalitat local. Aquesta tècnica s’ha emprat per a la detecció de vessaments de petroli a l’oceà a partir d’imatges SAR. Les contribucions d’aquest treball són a dos nivells. Per una banda, en la direcció del tractament de senyal multiescalar i, per una altra banda, en la direcció de la interpretació automàtica de les imatges SAR. Pel que fa al tractament de senyal multiescalar, es proposa una forma diferent d’utilitzar les descomposicions espai – escala (o, equivalentment, temps - freqüència). Pel tal d’aprofitar de forma més eficaç la informació ressaltada per la projecció, els mètodes proposats realitzen l’anàlisi directament al domini transformat. Pel que fa a la interpretació automàtica de les imatges SAR, s’ha demostrat en primer lloc l’adequació del marc multiescalar que es proposa en aquesta dissertació. Inscrites en aquest marc, les tècniques automàtiques proposades són senzilles, flexibles, robustes i autocontingudes.