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  • Articles  (1,190)
  • 2010-2014  (1,190)
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  • 1
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    Unknown
    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: The dual-wavelength Echidna lidar is a portable ground-based full-waveform terrestrial scanning lidar for characterization of fine-scale forest structure and biomass content. While scanning, the instrument records the full time series of returns at a half-nanosecond rate from two coaligned 5-ns pulsed lasers at 1064 and 1548 nm wavelengths. Leaves absorb more strongly at 1548 nm compared to stems, allowing discrimination of forest composition at milliradian scales from the ground to the forest canopy. This work describes the instrument design and data products and demonstrates the power of two wavelength lidar to clearly distinguish leaves from woody material with preliminary field data from the Sierra Nevada National Forest.
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    Electronic ISSN: 1558-0571
    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 2
    Publication Date: 2014-12-06
    Description: Snow changes its morphology permanently from the moment a snow flake touches the ground. Under the influence of meteorological factors such as temperature, humidity, and wind, snow grains form complex structures of ice bonds enclosing variable portions of air. The characteristics of such structures are important for the formation of snow avalanches. Certain snow types such as surface hoar, ice crusts, or windblown snow play a major role in the formation of weak layers and slabs, which are precondition for dangerous slab avalanches. The reflection properties of snow depend on the optical equivalent grain size of the ice particles that constitute the snow cover. High spatial resolution remote sensing instruments with near-infrared (0.7–1.4 $muhbox{m}$ ) bands are able to detect such differences in the optical reflection of snow. We use normalized difference index band ratios from a spaceborne and an airborne remote sensing instrument to distinguish and map different snow-surface types in the neighborhood of Davos, Switzerland, enabling a valuable visualization of the spatial variability of the snow surface.
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  • 3
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: In many real-world problems, data always lie in a low-dimensional manifold. Exploiting the manifold can greatly enhance the discrimination between different categories. In this letter, we propose a classification framework based on sparse representation to directly exploit the underlying manifold. Specifically, using the tangent plane to approximate the local manifold of each test sample, the proposed method classifies the sample by sparse representation in tangent space. Unlike several existing sparse-representation-based classification methods, which sparsely represent the test sample itself, the proposed method sparsely represents the local manifold of the test sample by tangent plane approximation. Therefore, it goes beyond the sample itself and is more robust to kinds of variations confronted in hyperspectral image (HSI) such as illustration differences and spectrum mixing. Experimental results show that the proposed algorithm outperforms several state-of-the-art methods for the classification of HSI with limited training samples.
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  • 4
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: Interferometric phase filtering is an indispensable step to obtain accurate measurement of digital elevation model and surface displacement. In the case of low-correlation or complicated topography, traditional phase filtering methods fail in balancing noise elimination and phase preservation, which leads to inaccurate interferometric phase. A new nonlocal interferometric phase filtering method taking advantage of higher order singular value decomposition (HOSVD) is proposed in this letter. For each pixel of the interferometric phase, a 3-D data array is established, and shrinkage is applied after HOSVD. A Wiener filter is used to improve the denoising performance in the end. Simulated and real data are employed to validate that the proposed method outperforms other traditional methods and some of the state-of-the-art nonlocal methods.
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  • 5
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: This letter proposes a new ship target detection method for very high resolution (VHR) synthetic aperture radar (SAR) images based on multilayer constant false alarm rate (CFAR). First, combined with log-normal distribution, a multilayer CFAR method is designed to overcome the holes and the fracture in the traditional detected results. This method can retain more details of ships and takes much less time than the traditional CFAR method for VHR SAR images. Second, based on a priori knowledge of ships, we use the sliding window to remove the false alarm targets. Finally, In order to measure the size and shape of a ship, we extract the outline of a ship and fill it by a level set method. Experimental results, carried out on real SAR images, demonstrate that the proposed approach outperforms the previous one in terms of the detection ratio of pixels instead of the number of ships.
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  • 6
    Publication Date: 2014-12-06
    Description: In this letter, it is shown that spaceborne observations made by the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite agreed closely with the Passive Active L-band System (PALS) brightness temperature acquisitions during the Soil Moisture Active Passive (SMAP) Validation Experiment 2012. The difference between the SMOS and PALS measurements was less than 5 K and 6 K for vertical and horizontal polarizations, respectively, over the relatively homogeneous agricultural areas. These values are less than the SMOS subpixel variability determined from the PALS measurement. This result demonstrated that the measurements obtained in the experiment are scalable to spaceborne brightness temperature observations, are representative of the expected SMAP observations, and will be of value in the development of soil moisture algorithms for spaceborne missions.
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  • 7
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: The potential of using log-cumulants for discrimination between mineral oil spills and other low-backscatter ocean features in synthetic aperture radar data is investigated here. Radarsat-2 fine quad-polarization data containing experimental oil spills, as well as simulated biogenic slicks and a natural phenomenon, are analyzed. For this data set, the combined information of matrix log-cumulants of first and second order is found to clearly discriminate the majority of the mineral oil spills from the simulated biogenic slicks and the natural phenomenon. These preliminary findings suggest that the proposed method has a potential application in classification of low-backscatter ocean features of unknown origin.
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  • 8
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: A brightness temperature ( $hbox{Tb}$ ) downscaling algorithm based on the synergy between active and passive microwave observations is tested using airborne data that simulate the Soil Moisture Active Passive (SMAP) mission of the National Aeronautics and Space Administration scheduled for launch in January 2015. While this algorithm has been adopted as the baseline for SMAP, it has only been tested on a limited variety of land uses and vegetation types. Consequently, this study evaluates the SMAP active/passive downscaling algorithm using data with varied conditions. The SMAP experiment conducted in Australia has been used for this purpose. The algorithm was applied over several 9 km $times$ 9 km pixels with different land covers, so as to evaluate the accuracy of this algorithm under different heterogeneity levels. Brightness temperatures were downscaled from 9 to 3 km (approximating the resolution ratio of SMAP downscaling approach) across nine days of data. Results show that the root-mean-square error of $hbox{Tb}$ in grassland could meet the 2.4-K target accuracy of SMAP, while in cropping, it was 2 K higher than the target. The influence from water bodies was also assessed and confirmed to have a significant impact if not removed prior to downscaling.
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  • 9
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    Unknown
    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: Hyperspectral imaging has gained significant interest in the past few decades, particularly in remote sensing applications. The considerably high spatial and spectral resolution of modern remotely sensed data often provides more accurate information about the scene. However, the complexity and dimensionality of such data, as well as potentially unwanted details embedded in the images, may act as a degrading factor in some applications such as classification. One solution to this issue is to utilize the spatial–spectral features to extract segments before the classification step. This preprocessing often leads to better classification results and a considerable decrease in computational time. In this letter, we propose a Pixon-based image segmentation method, which benefits from a preprocessing step based on partial differential equation to extract more homogenous segments. Moreover, a fast algorithm has been presented to adaptively tune the required parameters used in our Pixon-based schema. The acquired segments are then fed into the support vector machine classifier, and the final thematic class maps are produced. Experimental results on multi/hyperspectral data are encouraging to apply the proposed Pixons for classification.
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  • 10
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2014-12-06
    Description: Component substitution (CS) technique is a famous framework for merging multispectral (MS) and panchromatic (Pan) images. The synthetic intensity component is important in the CS fusion framework. In this letter, we propose an optimization model to obtain the adaptive weights. The adaptive weights are computed by maximizing an objective function, which measures the radiometric similarity between the low-scale intensity image and the spatially degraded Pan image. Correlation coefficient, mean-structural-similarity index, and mutual information are used as the similarity criteria, respectively. A particle-swarm-optimization algorithm is adopted to solve the single objection optimization problem. The proposed CS framework is compared with popular CS-based fusion methods. Visual analysis and quality results demonstrate that the proposed adaptive CS fusion framework has superior performance.
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