1,721,091 research outputs found
Two-layer hierarchical coding for MPEG2-video
No full textA two-layer scheme for MPEG-2 video that uses adaptive datapartitioning (ADP) is presented. The slice structure of the upper layer and a new synchronization procedure between the layers are defined. The experimental results prove the effectiveness of the two-layer model, particularly for increasing values of cell loss probability
Classification of polarimetric SAR images using adaptive neighbourhood structures
No full textTwo detail-preserving classification algorithms for polarimetric SAR images are proposed and their performance are evaluated on polarimetric complex SAR images. Neighbourhood structures are adaptively selected for modelling the polarimetric amplitudes and the region labels, and for achieving detail preservation. Experimental results obtained from multi-frequency polarimetric SAR images show that the novel schemes produce visual improvements for detail preservation, and exhibit equivalent or higher classification performance with respect to usual classification schemes
Pansharpening of multispectral images based on nonlocal parameter optimization
No full textHigh-quality pansharpened multispectral (MS) images are rarely obtained from fast, efficient, and robust algorithms. In most cases, effective pansharpening methods have huge computational complexity, as in the case of variational methods, or algorithms based on sparse representations. Moreover, injection models are often application dependent, not sufficiently general to be applied to different scenarios, and the resulting algorithm implementations cannot process large-size images. The proposed pansharpening method is accurate and fast and can be successfully applied to huge images. It also solves the problem of context-adaptive schemes that tune the spatial injection parameters on local statistics: Instabilities and blocky artifacts can be generated by pansharpening methods whose parameters are computed on local windows. The proposed method is an extension of the classical component-substitution algorithms: An optimal detail image (in the mmse sense) extracted from the panchromatic band is calculated for each MS band by evaluating band-dependent generalized intensities. It overcomes window-based local estimation of parameters by applying a nonlocal parameter optimization through K-means clustering. Very high quality scores, both at degraded and full scale, and excellent visual quality of the fused images demonstrate the validity of the method
Unsupervised VHR SAR change mapping
No full textThe paper presents an unsupervised procedure for change mapping from two very-high-resolution (VHR) SAR acquisitions. Following the approach proposed in [1], the method exploits the characteristics of a robust, parametric, high-order statistics change feature by extending it to a multiscale version, namely Multi-scale Kullback-Leibler (MKL) feature. Its effectiveness is experimentally confirmed on simulated and real VHR amplitude SAR image pairs. The thresholding algorithm is revisited, optimized and tested on true CosmoSkyMed (CSK) images. The experimental tests demonstrate the robustness and quality of the proposed change mapping method, which can be applied for damage assessment in disaster management systems
A review of image fusion algorithms based on the Super-Resolution paradigm
Full text linkA critical analysis of remote sensing image fusion methods based on the super-resolution (SR) paradigm is presented in this paper. Very recent algorithms have been selected among the pioneering studies adopting a new methodology and the most promising solutions. After introducing the concept of super-resolution and modeling the approach as a constrained optimization problem, different SR solutions for spatio-temporal fusion and pan-sharpening are reviewed and critically discussed. Concerning pan-sharpening, the well-known, simple, yet effective, proportional additive wavelet in the luminance component (AWLP) is adopted as a benchmark to assess the performance of the new SR-based pan-sharpening methods. The widespread quality indexes computed at degraded resolution, with the original multispectral image used as the reference, i.e., SAM (Spectral Angle Mapper) and ERGAS (Erreur Relative Globale Adimensionnelle de Synthèse), are finally presented. Considering these results, sparse representation and Bayesian approaches seem far from being mature to be adopted in operational pan-sharpening scenarios
Interband structure modeling for Pan-sharpening of very high resolution multispectral images
No full textThis paper addresses the modeling of wavelet coefficients for multispectral (MS) band sharpening based on undecimated multiresolution analysis (MRA). The coarse MS bands are sharpened by injecting highpass details taken from a high-resolution panchromatic (Pan) image. Besides the MRA, crucial point is modeling the relationships between detail coefficients of a generic MS band and the Pan image at the same resolution. Once calculated at the coarser resolution, where both types of data are available, such a model shall be extrapolated to the finer resolution in order to weight the Pan details to be injected. The goal is that the merged MS images are most similar to what the MS sensor would collect if it had the same resolution as the broadband Pan imager. Three injection models embedded in an ‘‘a` trous’’ wavelet decomposition will be described and compared on a test set of very high-resolution QuickBird MS + Pan data. Two models work on approximation and detail coefficients, respectively, and provide a certain degree of unmixing of coarse MS pixels. The third model is based on spectral fidelity of the merged image to the (resampled) original MS data, that is, no unmixing is attempted. It is much simpler than the other two because it does not require calculation of local statistics. Fusion comparisons on spatially degraded data, of which higher-resolution true MS data are available for reference, show that the former two models yield better results than the latter, in terms of both radiometric and spectral fidelity. The latter, however, yields a reliable sharpening unaffected by local artifacts, regardless of landscape complexity. When local statistics of wavelet coefficients are used, the model estimated on approximation yields slightly better but considerably stabler results than that calculated starting from bandpass details
Panchromatic sharpening of remote sensing images using a multiscale Kalman filter
No full textThis paper presents a solution to the problem of enhancing the spatial resolution of multispectral images with high-resolution panchromatic observations. The proposed method exploits the undecimated discrete wavelet transform, which is an octave bandpass representation achieved from a conventional discrete wavelet transform by omitting all decimators and up-sampling the wavelet filter bank, and the vector multiscale Kalman filter, which is used to model the injection process of wavelet details. Kalman modelization is exploited by spatial detail analysis at coarser scales in which multispectral and panchromatic representations are known. Results are presented and discussed on very-high resolution images acquired by Quickbird satellite systems. Fusion simulations on spatially degraded data and fusion tests at the full scale reveal that an accurate and reliable PAN-sharpening is achieved by the proposed method
Decimated geometric filter for edge-preserving smoothing of non-white image noise
No full textA procedure of recursive decimation is proposed to improve the performance of geometric filtering, in the case of spatially correlated image noise. Edges and fine textures are preserved, and noisy backgrounds carefully smoothed in a smaller number of iterations. Both SNR and subjective comparisons demonstrate an enhanced effectiveness with respect to geometric filtering. Such application fields as SAR speckle filtering and digital video processing are discussed and shown to benefit from the proposed scheme
A new selective ARQ scheme with a finite buffer
No full textAutomatic repeat request (ARQ) techniques with error-detecting codes are commonly used in communication systems. Of these, selective protocols, while the most efficient, have the notable drawback of requiring large buffers at the receiver side. A new selective ARQ protocol with a finite-length buffer is described in this paper. If N is the number of codewords transmittable in the round-trip delay, the described protocol requires a buffer having length equal to N + N-a, N-a greater than or equal to 2 being an integer. A lower bound on the throughput of the described ARQ protocol is derived. The proposed protocol achieves higher throughputs than similar schemes, giving comparable results to selective protocols with infinite-length buffers for high error rates in the communication channel
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