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Feature extraction and image classification using polarimetric synthetic aperture radar (PolSAR) images are currently of great interest in SAR applications. Generally, PolSAR image classification is a high-dimensional nonlinear mapping problem. Sparse representation-based techniques have shown great potential for pattern recognition problems. Therefore, on the basis of the sparse characteristics of the features for PolSAR image classification, a supervised PolSAR image classification method based on sparse representation is proposed in this paper. First, the effective features are extracted to describe the distinction of each class. Then, the feature vectors of the training samples construct an over-complete dictionary and obtain the corresponding sparse coefficients; meanwhile, the residual error of the pending pixel with respect to each atom is evaluated and considered as the criteria for classification, and the ultimate class results can be obtained according to the atoms with the least residual error. In addition, a Simplified Matching Pursuit (SMP) algorithm is proposed to solve the optimization problem of sparse representation of PolSAR images. The verification tests are implemented using Danish EMISAR L-band fully polarimetric SAR data of Foulum area, Denmark. The preliminary experimental results confirm that the proposed method outputs an excellent result and moreover the classification process is simpler and less time consuming.

The first crustal‐scale controlled source seismic refraction experiment in the southern Korean Peninsula, KCRUST2002, was carried out along a 300‐km long profile across this peninsula in December 2002. Iterative processing and modeling produced a laterally varying layered crustal velocity model. The crust is thickest (34 km) below the Okcheon fold belt in the middle of the transect and thinnest (28 km) at the eastern end where the Cretaceous Gyeongsang basin is characterized by 5 km of low velocity material that constitutes the upper crust. The P velocities in upper and lower crust range from 5.4 to 6.0 km/s and from 6.4 to 6.7 km/s, respectively. The average crustal Poisson's ratio is found to be 0.25–0.27 (Vp/Vs = 1.73−1.78) along the profile. A mid‐crustal velocity discontinuity is recognized in the northwestern part of the transect. The underlying mantle has velocities in the range of 7.9–8.1 km/s.

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International audienceThis study aims to understand the effects of the topographic slope variation on the vegetation backscattering characteristics of polarimetric imaging radar. Most of the previous studies in modeling microwave backscattering signatures of vegetated area have been carried out over relatively flat areas. In order to model vegetation scattering mechanisms of mountainous forests, this paper presents an improvement of the radiative transfer model that accounts for the tilted scattering surface beneath a forest canopy. An L-band polarimetric synthetic aperture radar (SAR) data set acquired by the NASA/Jet Propulsion Laboratory Airborne SAR system was used to test and to assess the vegetation scattering model for a sloping forest area. Experimental result shows the proposed model to be adequate for evaluating slope-induced changes in microwave scattering mechanisms

Near‐inertial (∼18 hours) internal waves were observed in the mid‐western part of the East Sea on May 18 and 19, 2004 using C‐band Synthetic Aperture Radar (SAR) images. Current and temperature measurements obtained during the field experiment from 10 May to 9 June 2004 (IWXES2004, Internal Wave eXperiment in the East Sea), were analyzed to investigate the processes by which near‐inertial internal waves can be seen in SAR images and how they progress. The spatial distributions of horizontal wavelength and phase speed estimated from two successively acquired SAR images are consistent with those inferred from water temperature and current measurements carried out during the field experiment. Based on these two independent observations (SAR and IWXES2004), we report a strong possibility that the observed wave patterns in the SAR images during IWXES2004 are near‐inertial internal waves propagating westward off the east coast of the Korean peninsula with a phase speed of about 0.3 m/s.

Abstract:In order to better constrain the utility of multispectral datasets in the characterization of surface materials, Landsat Thematic Mapper (TM) data were evaluated in the discrimination of geological classes in the Cape Smith Belt of Quebec, a greenstone belt that hosts Early Proterozoic units including those of the Purtuniq ophiolite. Ground-based measurements collected for the study area highlight the importance of chemical alteration in controlling the reflectance properties of key geological classes. The spatial distribution of exposed lithologies in the study area was determined through (1) image classification using a feedforward backpropagation neural network classifier; and (2) generation of fraction images for spectral end members using a linear unmixing algorithm and ground reflectance data. Despite some shortcomings, the database of surface cover generated by the neural network classifier is a useful representation of the spatial distribution of exposed geological materials in the study area, with an overall agreement with ground truth of 87.7%. In contrast, the fraction images generated through unmixing are poor representations of ground truth for several key lithological classes. These results underscore both the considerable utility and marked limitations of Landsat TM data in the mapping of igneous and metamorphic lithologies.