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  • Articles  (440)
  • 2010-2014  (440)
  • 2012  (440)
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  • Articles  (440)
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  • 2010-2014  (440)
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  • 1
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    Initial Validation of SMOS Vegetation Optical Thickness in Iowa (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: The European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite mission provides microwave L-band measurements of vegetation optical thickness over the Earth. Optical thickness is related to water held in vegetation. The water content of crops varies over the growing season from a minimum during planting to a maximum during reproduction and back to a minimum during senescence. We found that in Iowa in 2010 the change in SMOS optical thickness over the growing season can be related to crop yields. However, there are inconsistencies in the optical thickness data, particularly high-frequency variation and unexpected changes outside of the growing season. We hypothesize that the unexpected changes during the dormant periods are due to changes in soil surface roughness caused by land management activities and show a relationship between changes in roughness and changes in optical thickness, which may be confusing the SMOS retrieval algorithm.
    Print ISSN: 1545-598X
    Electronic ISSN: 1558-0571
    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 2
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    Registration of Optical and SAR Satellite Images by Exploring the Spatial Relationship of the Improved SIFT (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: Although feature-based methods have been successfully developed in the past decades for the registration of optical images, the registration of optical and synthetic aperture radar (SAR) images is still a challenging problem in remote sensing. In this letter, an improved version of the scale-invariant feature transform is first proposed to obtain initial matching features from optical and SAR images. Then, the initial matching features are refined by exploring their spatial relationship. The refined feature matches are finally used for estimating registration parameters. Experimental results have shown the effectiveness of the proposed method.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 3
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    Wavelet Packet Analysis and Gray Model for Feature Extraction of Hyperspectral Data (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: Wavelet packet analysis (WPA) and gray model (GM) are investigated for nonlinear unsupervised feature extraction of hyperspectral remote sensing data in this letter. Treated as derivative series, a hyperspectral response curve of each pixel is decomposed into an approximation and various detailed compositions by WPA, and then, GM is continuously applied to find the relationship among those detailed compositions. Cluster–space representation is used for determining the optimal wavelet. New extracted features can reveal the intrinsic identities of hyperspectral data. Experimental results show the feasibility and reliability of our proposed method in terms of classification accuracy.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 4
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    Unsupervised Change Detection on SAR Images Using Triplet Markov Field Model (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: The triplet Markov field (TMF) model is powerful in the nonstationary synthetic aperture radar (SAR) image analysis. Taking the speckle noise and the correlation of nonstationarities in two multitemporal SAR images into account, we propose a change-detection method based on the TMF model in this letter. The third field $U$ in the TMF model is redefined to describe the nonstationary textural similarity between the two images for change detection. The corresponding prior energy of $(X, U)$ is reconstructed. The adaptive weight parameter in prior energy is introduced to cope with the detection tradeoff issue. An automatic estimation of the parameter is obtained with low level of complexity. The Bayesian maximum posterior marginal criterion is utilized with the TMF model to obtain change detection. Experimental results on real SAR images validate the superiority of the proposed TMF method over the Markov random field method.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 5
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    RFI Mitigation Using Two-Scale Estimators for Statistical Variance (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: The well-known sample variance estimator utilizes $N$ samples from a random process to first estimate the process mean. The estimator then uses the same $N$ samples to estimate variance from this mean. Process variance could also be estimated by first using less than $N$ samples to estimate the mean, followed by using all $N$ samples to estimate variance. Two-scale estimators of this type, both causal and noncausal, are defined. Statistics for these estimators are derived, which are valid for samples from any statistical distribution. These statistics are used to improve analysis of a previously reported device called the double detector. In microwave radiometry, the double detector senses the presence of deterministic signals, often called radio-frequency interference, that corrupt the usual measurement consisting only of Planck radiation.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 6
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    LiDAR Point Cloud Registration by Image Detection Technique (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: In this letter, a novel approach that utilizes the spectrum information (i.e., images) provided in a modern light detection and ranging (LiDAR) sensor is proposed for the registration of multistation LiDAR data sets. First, the conjugate points in the images collected at varied LiDAR stations are extracted through the speedup robust feature technique. Then, by applying the image–object space mapping technique, the 3-D coordinates of the conjugate image points can be obtained. Those identified 3-D conjugate points are then fed into a registration model so that the transformation parameters can be immediately solved using the efficient noniterative solution to linear transformations technique. Based on numerical results from a case study, it has been demonstrated that, by implementing the proposed approach, a fully automatic and reliable registration of multistation LiDAR point clouds can be achieved without the need for any human intervention.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 7
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    Selection of Landmark Points on Nonlinear Manifolds for Spectral Unmixing Using Local Homogeneity (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: Endmember extraction and unmixing methods that exploit nonlinearity in hyperspectral data are receiving increased attention, but they have significant challenges. Global feature extraction methods such as isometric feature mapping have significant computational overhead, which is often addressed for the classification problem via landmark-based methods. Because landmark approaches are approximation methods, experimental results are often highly variable. We propose a new robust landmark selection method for the purpose of pixel unmixing that exploits spectral and spatial homogeneity in a local window kernel. We compare the performance of the method to several landmark selection methods in terms of reconstruction error and processing time.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 8
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    Airborne Dual-Polarization Observations of the Sea Surface NRCS at C-Band in High Winds (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2012-12-20
    Description: Airborne dual-polarization observations of sea surface normalized radar cross section (NRCS) were conducted over the North Atlantic during January–February 2011. Observations were made using the University of Massachusetts' Imaging Wind and Rain Airborne Profiler radar system installed on the National Oceanic and Atmospheric Administration's WP-3D research aircraft during several winter storm events to determine the high-wind response of the sea surface NRCS for both horizontal and vertical polarizations. During the flights, the aircraft performed several constant-roll circle maneuvers to allow collection of NRCS over a range of incidence angles. We find consistency with prior reports in the polarization ratio observed at moderate incidence angles at the winds encountered. For larger incidence angles, we observe a measurable decrease in polarization ratio with increasing wind speed.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
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  • 9
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    An Improved SAC Algorithm Based on the Range-Keystone Transform for Doppler Rate Estimation (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
    Details
    Publication Date: 2012-12-20
    Description: Doppler rate is an important parameter in synthetic aperture radar (SAR) signal processing since it affects the SAR image focusing. There are many approaches to estimate the Doppler rate from SAR data; however, some approaches are not appropriate for spotlight SAR, which is focused with the two-step algorithm, since, after azimuth preprocessing, the signal is aliased in the azimuth time domain. Although the shift-and-correlation (SAC) algorithm may be suitable for such signals, it is proposed for the stripmap imaging mode; and when it is used to estimate the Doppler rate for spotlight SAR, some problems, such as the high computational load from zero padding and the constraint of the focus depth, may occur. In this letter, an improved Doppler rate estimation approach, which is called the Keystone–SAC algorithm, is proposed. An iterative scheme is presented to estimate the ambiguity number, and a special case when the ambiguity number splits into two numbers is analyzed. The real spotlight SAR data processing results are used to validate the effectiveness of the proposed algorithm.
    Print ISSN: 1545-598X
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 10
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    Automatic Annotation of Satellite Images via Multifeature Joint Sparse Coding With Spatial Relation Constraint (2012)
    Institute of Electrical and Electronics Engineers (IEEE)
    Details
    Publication Date: 2012-12-20
    Description: In this letter, we propose a novel framework for large-satellite-image annotation using multifeature joint sparse coding (MFJSC) with spatial relation constraint. The MFJSC model imposes an $l_{1, 2}$ -mixed-norm regularization on encoded coefficients of features. The regularization will encourage the coefficients to share a common sparsity pattern, which will preserve the cross-feature information and eliminate the constraint that they must have identical coefficients. Spatial dependences between patches of large images are useful for the annotation task but are usually ignored or insufficiently exploited in other methods. In this letter, we design a spatial-relation-constrained classifier to utilize the output of MFJSC and the spatial dependences to annotate images more precisely. Experiments on a data set of 21 land-use classes and QuickBird images show the discriminative power of MFJSC and the effectiveness of our annotation framework.
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    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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