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Hyperspectral Image Classification Based on Relaxed Clustering Assumption and Spatial Laplace Regularizer (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: In this letter, a relaxed clustering assumption and spatial Laplace-regularizer-based semisupervised hyperspectral image classifier is proposed. Considering the mixed pixels and noise intrinsic in hyperspectral image, we relax the clustering assumption employed in most of the available classifiers so that the similar hyperspectral vectors tend to share the “similar” labels instead of the “same” label, to formulate a modified spectral similarity regularizer. Moreover, the spatial homogeneity assumption is cast on hyperspectral pixels to construct a spatial regularizer, to overcome the salt-and-pepper misclassification of images. The effectiveness of our proposed method is evaluated via experiments on AVIRIS data, and the results show that it exhibits state-of-the-art performance, particularly when there are a small number of training samples.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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An Amplitude-Preserved Time–Frequency Peak Filtering Based on Empirical Mode Decomposition for Seismic Random Noise Reduction (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: Time–frequency peak filtering (TFPF) is a classical filtering method in time-frequency domain. It applies Wigner–Ville distribution to estimate the instantaneous frequency of an analytical signal. There is a pair of contradiction in this method, i.e., selecting a short window length may lead to good preservation for signal amplitude but bad random noise reduction whereas selecting a long window length may lead to serious attenuation for signal amplitude but effective random noise reduction. In order to make a good tradeoff between valid signal amplitude preservation and random noise reduction, we adopt empirical mode decomposition (EMD) to improve the TFPF results. The new idea is to utilize the decomposition characteristic of EMD which decomposes a signal to several modes from high to low frequency and to take advantage of the time-frequency filtering characteristic of TFPF which can recognize the valid signal component in the time-frequency plane in order to achieve effective random noise reduction together with good amplitude preservation. Through some experiments on synthetic seismic models and field seismic records, we show the better performance of the new method compared with the conventional TFPF.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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Classification of Very High Spatial Resolution Imagery Based on a New Pixel Shape Feature Set (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: This letter presents a novel spatial features extraction method for the high spatial resolution multispectral imagery (HSRMI) classification. First, Canny filter algorithm is applied to extract the edge information to obtain the fuzzy edge map. Secondly, adaptive threshold value for each pixel's homogeneous region (PHR) calculation is determined based on the fuzzy edge map and original image. Next, the PHR for every pixel is obtained based on the fuzzy edge map, adaptive threshold value and original image. And then, the pixel shape feature set (PSFS) is extracted based on the PHR. Lastly, SVM classifier is applied to classify the hybrid spectral and PSFS. Two different experiments were performed to evaluate the performance of PSFS, in comparison with spectral, gray level co-occurrence matrix (GLCM) and the existing pixel shape index (PSI). Experimental results indicate that the PSFS achieved the highest accuracy, hence, providing an effective spectral–spatial classification method for the HSRMI.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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SAR Image Filtering Based on the Cauchy–Rayleigh Mixture Model (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: In this letter, a novel maximum a posteriori (MAP) filter for synthetic aperture radar (SAR) images is developed. We characterize the return signal of SAR using the Cauchy-Rayleigh mixture model, which is an approximation to the heavy-tailed Rayleigh distribution. The parameters of the Cauchy–Rayleigh mixture model are estimated from the noisy observation by using the expectation–maximization algorithm. Finally, we compare the proposed filter with several classical spatial filtering techniques by applying them on simulated data and various real SAR images. Experimental results show that the Cauchy–Rayleigh-mixture-based MAP filter performs better for speckle removal than the other methods, including Lee, Kuan, and $Gamma$ -MAP.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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Adaptive Through-Wall Indication of Human Target with Different Motions (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: Through-wall indication of human targets is highly desired in many applications. Generally, human targets behind wall are noncooperative, and rare prior knowledge about the circumstance behind wall could be available. Thus, it requires the ability to indicate human targets with different motions from clutters. To investigate this problem, we first examine the conventional time-domain indication methods, and find that their performances are controlled by the historical pulse number adopted to estimate background, which corresponds to the tap-length from the angle of filter. Then, based on an intermittent mode of human target echoes, we define the optimum tap-length as the shortest tap-length that makes the filter output signal-to-clutter-and-noise ratio reach maximum and develop an adaptive indication method with a gradient tap-length control scheme to search the optimum tap-length. Finally, through-wall experiments with an impulse through-wall radar demonstrate that the proposed method can obtain a good adaptive indication performance on human target with different motions.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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Determination of Local Slope on the Greenland Ice Sheet Using a Multibeam Photon-Counting Lidar in Preparation for the ICESat-2 Mission (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: The greatest changes in elevation in Greenland and Antarctica are happening along the margins of the ice sheets where the surface frequently has significant slopes. For this reason, the upcoming Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission utilizes pairs of laser altimeter beams that are perpendicular to the flight direction in order to extract slope information in addition to elevation. The Multiple Altimeter Beam Experimental Lidar (MABEL) is a high-altitude airborne laser altimeter designed as a simulator for ICESat-2. The MABEL design uses multiple beams at fixed angles and allows for local slope determination. Here, we present local slopes as determined by MABEL and compare them to those determined by the Airborne Topographic Mapper (ATM) over the same flight lines in Greenland. We make these comparisons with consideration for the planned ICESat-2 beam geometry. Results indicate that the mean slope residuals between MABEL and ATM remain small ( $〈$ 0.05 $^{circ}$ ) through a wide range of localized slopes using ICESat-2 beam geometry. Furthermore, when MABEL data are subsampled by a factor of 4 to mimic the planned ICESat-2 transmit-energy configuration, the results are indistinguishable from the full-data-rate analysis. Results from MABEL suggest that ICESat-2 beam geometry and transmit-energy configuration are appropriate for the determination of slope on $sim$ 90-m spatial scales, a measurement that will be fundamental to deconvolving the effects of surface slope from the ice-sheet surface change derived from ICESat-2.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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7

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Real-Time Implementation of the Pixel Purity Index Algorithm for Endmember Identification on GPUs (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: Spectral unmixing amounts to automatically finding the signatures of pure spectral components (called endmembers in the hyperspectral imaging literature) and their associated abundance fractions in each pixel of the hyperspectral image. Many algorithms have been proposed to automatically find spectral endmembers in hyperspectral data sets. Perhaps one of the most popular ones is the pixel purity index (PPI), which is available in the ENVI software from Exelis Visual Information Solutions. This algorithm identifies the endmembers as the pixels with maxima projection values after projections onto a large randomly generated set of random vectors (called skewers). Although the algorithm has been widely used in the spectral unmixing community, it is highly time consuming as its precision asymptotically increases. Due to its high computational complexity, the PPI algorithm has been recently implemented in several high-performance computing architectures, including commodity clusters, heterogeneous and distributed systems, field programmable gate arrays, and graphics processing units (GPUs). In this letter, we present an improved GPU implementation of the PPI algorithm, which provides real-time performance for the first time in the literature.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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A Principal Component Based Haze Masking Method for Visible Images (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: Land surfaces are commonly obstructed by haze in remote sensing images, which reduces the available land cover information. Haze detection is therefore important for locating, avoiding, or restoring hazy regions. In this letter, a principal component (PC)-based haze masking (PCHM) method is developed for the masking of haze in visible remote sensing images covering land surfaces at middle latitudes. Owing to the evidence of haze in the second PC, the PCHM method results in accurate haze masks. The complete procedure comprises two steps: haze construction and spatial optimization. The validity of the PCHM method is demonstrated through its application to several hazy visible images clipped from Landsat Enhanced Thematic Mapper Plus scenes. The quantitative assessments verify the superiority of the proposed method over the haze optimized transformation method for the production of binary haze masks. In addition, the resulting haze masks are compared with a MODIS cloud product, which further proves the necessity and validity of the proposed method.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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9

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Markovian Change Detection of Urban Areas Using Very High Resolution Complex SAR Images (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: In this letter, an innovative technique for change detection in urban areas using very high resolution synthetic aperture radar multichannel stacks is proposed. Instead of using the amplitude image, as in classical change detection approaches, the proposed technique uses the full complex image in a Markovian framework. The complex data are modeled using Markov random field hyperparameters, which are particular local parameters that take into account the spatial correlation between pixels. Starting from two data sets, the pre- and the postevent ones, the proposed algorithm, first, estimates the two hyperparameter maps and, then, compares the similarity between them. If a change occurs between the pre- and the postevent acquisitions, the statistical distribution of the hyperparameter maps will change. The maximum distance between the two obtained statistical distributions provides an index of changes. This sort of spatial correlation maps is computed using statistical estimation techniques, while the similarity comparison is computed using the two-step Kolmogorov–Smirnov statistic test. The algorithm is validated on simulated data and tested on real COSMO-SkyMed data acquired on the area of Naples, showing interesting and promising results.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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A Separately Determining Anisotropic Formation Parameter Method for Triaxial Induction Data (2013)

Institute of Electrical and Electronics Engineers (IEEE)

In: IEEE Geoscience and Remote Sensing Letters

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Publikationsdatum: 2013-12-14

Beschreibung: This letter describes a method to extract the unknown parameters of the formation using triaxial induction data based on the whole-space model. Two single-parameter coupled functions are constructed to determine the horizontal conductivity and the relative dip. After that, the vertical conductivity is solved analytically using another single-parameter function. The method is extremely fast and can be implemented for real-time processing and interpretation to allow decision making on the well site. The results can be further refined via postprocessing while the relative dip is required to be constant within an interval.

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Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie , Geologie und Paläontologie

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