By Topic

Geoscience and Remote Sensing Letters, IEEE

Issue 5 • Date Sept. 2011

Filter Results

Displaying Results 1 - 25 of 41
  • [Front cover]

    Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (243 KB)  
    Freely Available from IEEE
  • IEEE Geoscience and Remote Sensing Letters publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (41 KB)  
    Freely Available from IEEE
  • Table of contents

    Page(s): 837 - 838
    Save to Project icon | Request Permissions | PDF file iconPDF (49 KB)  
    Freely Available from IEEE
  • A Multispectral Canopy LiDAR Demonstrator Project

    Page(s): 839 - 843
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    The first demonstration of a multispectral light detection and ranging (LiDAR) optimized for detailed structure and physiology measurements in forest ecosystems is described. The basic principle is to utilize, in a single instrument, both the capacity of multispectral sensing to measure plant physiology [through normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI)] with the ability of LiDAR to measure vertical structure information and generate “hot spot” (specular) reflectance data independent of solar illumination. A tunable laser operated at four wavelengths (531, 550, 660, and 780 nm) was used to measure profiles of the NDVI and the PRI. Laboratory-based measurements were conducted for live trees, demonstrating that realistic values of the indexes can be measured. A model-based analysis demonstrates that the LiDAR waveforms cannot only capture the tree height information but also picks up the seasonal and vertical variation of NDVI inside the tree canopy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Regularized Multiresolution Spatial Unmixing for ENVISAT/MERIS and Landsat/TM Image Fusion

    Page(s): 844 - 848
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (639 KB) |  | HTML iconHTML  

    Earth observation satellites currently provide a large volume of images at different scales. Most of these satellites provide global coverage with a revisit time that usually depends on the instrument characteristics and performance. Typically, medium-spatial-resolution instruments provide better spectral and temporal resolutions than mapping-oriented high-spatial-resolution multispectral sensors. However, in order to monitor a given area of interest, users demand images with the best resolution available, which cannot be reached using a single sensor. In this context, image fusion may be effective to merge information from different data sources. In this letter, an image fusion approach based on multiresolution and multisource spatial unmixing is used to obtain a composite image with the spectral and temporal characteristics of medium-spatial-resolution instrument along with the spatial resolution of high-spatial-resolution image. A time series of Landsat/TM and ENVISAT/MERIS Full Resolution images acquired in the 2004 European Space Agency (ESA) Spectra Barrax Campaign illustrates the method's capabilities. The qualitative and quantitative assessments of the product images are given. The proposed methodology is general enough to be applied to similar sensors, such as the multispectral instruments which will fly on board the ESA GMES Sentinel-2 and Sentinel-3 upcoming satellite series. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Infrared-Based Measurements of Velocity, Turbulent Kinetic Energy, and Dissipation at the Water Surface in a Tidal River

    Page(s): 849 - 853
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (871 KB)  

    Thermal infrared (IR)-based particle image ve locimetry (PIV) is used to measure the evolution of velocity, turbulent kinetic energy (TKE), and the TKE dissipation rate at the water surface in the tidally influenced Snohomish River. Patterns of temperature variability in the IR imagery arise from disruption of the cool-skin layer and are used to estimate the 2-D velocity field. Comparisons of IR-based PIV mean velocity made with a colocated acoustic velocimeter demonstrate high cor relation (r2 >; 0.9). Over a tidal period, surface TKE computed from the IR velocity varies from 10-4 to 3 × 10-3 J · kg-1, with an average difference from the in situ measurements of 8%. IR-derived TKE dissipation rates vary from approximately 3 × 10-6 to 2 × 10-4 W · kg-1 at peak ebb, agreeing on average to within 7% of the in situ velocimeter results. IR-based PIV provides detailed measurements of previously inaccessible surface velocities and turbulence statistics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiscale Contour Extraction Using a Level Set Method in Optical Satellite Images

    Page(s): 854 - 858
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    This letter presents a novel coarse-to-fine level set method for contour extraction in optical satellite images. To distinguish objects from a background, the undecimated wavelet transform is firstly adopted to extract image features, and a homogeneity metric is defined to measure the variation of the features inside and outside contours. In addition, the weight distribution ratio is proposed to adaptively tune the relative weight of the features. Based on the homogeneity metric and the weight distribution ratio, a novel energy functional is developed to model a contour extraction problem, and in order to reduce the computation burden, a coarse-to-fine scheme is applied to progressively extract contours in finer scale, during which a contour position constraint is introduced to limit contours evolving in a small space around the candidate contours extracted in coarser scale. Extensive experiments have been carried out on optical satellite images to validate the proposed method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Complex Dielectric Measurements of Forest Fire Ash at X-Band Frequencies

    Page(s): 859 - 863
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (639 KB) |  | HTML iconHTML  

    Dielectric measurements of powdered forest fire ash have been investigated and presented using the Nicholson-Ross-Weir method within a WR-90 waveguide (X-band 8-12 GHz). The dielectric measurements of five samples have been outlined and taken at a room temperature of 22.8 °C. Permittivity ε for five different species has been presented within this letter. These include Eucalypt, Bracken Fern, She Oak, Wattle, and Cypress. The Eucalypt sample was tested dry and with a 30% moisture content by weight. The dry Eucalypt sample was found to have a permittivity value of approximately 2.32 ± 0.025 with a loss tangent of 0.005 ± 0.0025. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Thermal Expansion Component of Persistent Scatterer Interferometry Observations

    Page(s): 864 - 868
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1667 KB) |  | HTML iconHTML  

    This letter focuses on the thermal expansion component of persistent scatterer (PS) interferometry (PSI), which is a result of temperature differences in the imaged area between synthetic aperture radar (SAR) acquisitions. This letter is based on very high resolution X-band StripMap SAR data captured by the TerraSAR-X spaceborne sensor. The X-band SAR interferometric phases are highly influenced by the thermal dilation of the imaged objects. This phenomenon can have a strong impact on the PSI products, particularly on the deformation velocity maps, if not properly handled during the PSI analysis. In this letter, we propose a strategy to deal with the thermal dilation phase component, which involves further developing the standard two-parameter PSI model (deformation velocity and residual topographic error) with a third unknown parameter called the thermal dilation parameter, which is estimated for each PS. The map obtained from plotting this parameter for all PSs of a given area is hereafter called thermal map. This letter describes the proposed model and outlines the issue of parameter estimability. In addition, the potential of exploiting the thermal maps is analyzed by illustrating two examples of the Barcelona (Spain) metropolitan area. Thermal maps provide two types of information: The first one is the coefficient of thermal expansion of the observed objects, while the second one, which is related to the pattern of the thermal dilation parameter, gives information about the static structure of these objects. Two important aspects that influence the exploitation of thermal maps are discussed in the last section of this letter: the line-of-sight nature of the derived estimates and the achievable precision in the estimation of the coefficient of thermal expansion. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced Visualization of Hyperspectral Images

    Page(s): 869 - 873
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    We present an enhanced visualization algorithm for hyperspectral images (HSIs). The visualization is based on the projection onto color matching functions of the human vision system. A contrast enhancement procedure is introduced by the fusion of the gradient information of the individual HSI bands. Both visualization and enhancement are combined into a multiresolution framework using wavelets. The HSI is transformed into a specific representation (HSI wavelet representation), in which the enhancement is performed at the level of the wavelet detail subbands, whereas the visualization is performed at the level of the low-resolution subbands. Specific objective quality measures are applied to demonstrate that the proposed procedure provides visualization results with a high contrast. Results are compared with state-of-the-art HSI visualization techniques and with the postprocessing enhancement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Noise Attenuation for 2-D Seismic Data by Radial-Trace Time-Frequency Peak Filtering

    Page(s): 874 - 878
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1559 KB) |  | HTML iconHTML  

    The time-frequency peak filtering (TFPF) is an effective tool in random-noise attenuation and has been applied to seismic record denoising in recent years. The window length (WL) of the time-frequency distribution (TFD) is the key to the conventional TFPF technology. A fixed WL is not optimal for both the low- and high-frequency components at the same time; an adaptive WL results in serious distortion of the reflected waveform. In this letter, we discuss a modified TFPF along the radial-trace direction and prove its advantage in TFD window selection. Experiments on both synthetic models and field data show that the radial-trace TFPF result is no longer much influenced by the WL as the conventional TFPF. Furthermore, it can provide better performance in both random-noise attenuation and reflected signal preservation with a fixed WL. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Soft-Change Detection in Optical Satellite Images

    Page(s): 879 - 883
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (501 KB) |  | HTML iconHTML  

    In this letter, we propose a novel approach for unsupervised change detection in multitemporal optical satellite images. Unlike the traditional methods, the proposed method, called the soft-change detection, models the change detection as a transparency computation problem and assigns to each pixel a set of soft labels. In order to extract the pixel opacity, we optimize an objective function by exploiting the Bayesian matting method. Comparisons between the proposed method and the state-of-the-art methods are reported. Experimental results demonstrate the effectiveness of the proposed method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient Strip-Mode SAR Raw-Data Simulation of Fixed and Moving Targets

    Page(s): 884 - 888
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    The performance of the high-resolution synthetic aperture radar (SAR) with moving-target indication and imaging systems can be analyzed and evaluated by modeling the whole imaging system through a simulation. The raw-data generation in the time domain achieves a realistic simulation procedure provided that computational complexity can be tolerable. In this letter, we proposed an efficient SAR raw-data generator of a scene that includes both static and moving targets. The raw data set of an extended scene and the moving target is simulated in the frequency domain separately and superposed in the time domain. The generated raw data for fixed and moving targets are also processed and analyzed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of Multiple-Instance Learning for Hyperspectral Image Analysis

    Page(s): 889 - 893
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (407 KB) |  | HTML iconHTML  

    Multiple-instance learning (MIL) is a learning paradigm used for learning a target concept in the presence of noise or with an uncertainty in target information including class labels. Due to the difficult situations in which hyperspectral images (HSIs) are collected, research in this area is extremely relevant and directly applicable. In the following, an MIL framework is proposed for target spectra learning for HSI analysis. MIL techniques are compared to their non-MIL counterparts (standard machine learning techniques). Experimental results indicate that MIL can learn target spectra with a lack of target information and, furthermore, result in improved classifiers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Locality-Preserving Discriminant Analysis in Kernel-Induced Feature Spaces for Hyperspectral Image Classification

    Page(s): 894 - 898
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (666 KB) |  | HTML iconHTML  

    Linear discriminant analysis (LDA) has been widely applied for hyperspectral image (HSI) analysis as a popular method for feature extraction and dimensionality reduction. Linear methods such as LDA work well for unimodal Gaussian class-conditional distributions. However, when data samples between classes are nonlinearly separated in the input space, linear methods such as LDA are expected to fail. The kernel discriminant analysis (KDA) attempts to address this issue by mapping data in the input space onto a subspace such that Fisher's ratio in an intermediate (higher-dimensional) kernel-induced space is maximized. In recent studies with HSI data, KDA has been shown to outperform LDA, particularly when the data distributions are non-Gaussian and multimodal, such as when pixels represent target classes severely mixed with background classes. In this letter, a modified KDA algorithm, i.e., kernel local Fisher discriminant analysis (KLFDA), is studied for HSI analysis. Unlike KDA, KLFDA imposes an additional constraint on the mapping-it ensures that neighboring points in the input space stay close-by in the projected subspace and vice versa. Classification experiments with a challenging HSI task demonstrate that this approach outperforms current state-of-the-art HSI-classification methods. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Rotation Estimation for ISAR Targets With a Space–Time Analysis Technique

    Page(s): 899 - 903
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (357 KB) |  | HTML iconHTML  

    A new method for estimating the rotational motion of a noncooperative target is presented by exploiting the 2-D space-variant characteristic of inverse synthetic aperture radar imaging. With a space-time analysis technique, the position variation of every extracted scattering center in both the range and cross-range directions can be utilized for rotation estimation. This method differs substantially from conventional methods that exploit high-order terms of the Doppler frequency, i.e., only the position variation in the cross-range direction. An iterative processing scheme is proposed to extract as many scattering centers as possible from the phase history of returned echoes. Experimental results with some measured airplane data demonstrate the effectiveness of the proposed method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the Use of Feature Selection for Classifying Multitemporal Radarsat-1 Images for Forest Mapping

    Page(s): 904 - 908
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (294 KB) |  | HTML iconHTML  

    As the number of satelliteborne SAR systems increases, both the availability and the length of multitemporal (MT) sequences of SAR images have also increased. Reported research with MT SAR sequences suggests that they increase the classification accuracy for all applications over single-date images. The length of the MT SAR sequences reported in the literature is still quite modest: on the order of six images. As the length of a sequence increases, the selection of images to use in a classification becomes important. The current practice is to add scenes chronologically, and some researchers have suggested that image selection does not affect classification accuracy. Our research explored the problem of image selection in MT SAR classification. We compared the chronological selection scheme with two feature selection algorithms: a very simple algorithm and a more complex class-based algorithm. We found that, while the simple feature selection algorithm was more efficient than chronological selection, yielding peak accuracy with few features, it saturated at the same accuracy as chronological selection. The more complex algorithm was significantly more accurate than chronological selection, even with just two features. Our results suggest that the use of a feature selection algorithm produces more efficient and more accurate classification results than chronological selection. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatiotemporal Segmentation of Spaceborne Passive Microwave Data for Change Detection

    Page(s): 909 - 913
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (503 KB) |  | HTML iconHTML  

    Highly repetitive global-scale remote sensing systems, such as the Special Sensor Microwave/Imager (SSM/I), provide essential tools for monitoring changes on the Earth's surface. This letter presents a time-series segmentation and classification method to identify surface changes and to estimate the duration (days) for the changes using daily SSM/I observations. The method was developed based on a bottom-up segmentation algorithm for time-series data. The attributes of the linear segments provide the basis for understanding and classifying the surface changes. In the application examples, we calculated the number of surface snowmelt days at various locations on the Antarctic Ice Sheet by classifying the segmented time series of SSM/I brightness temperature observations. It is demonstrated that this novel method is robust to the data noise and efficient for processing large volume of spatially and temporally continuous remote sensing data for environmental monitoring. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Inpainting Strategies for Reconstruction of Missing Data in VHR Images

    Page(s): 914 - 918
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (661 KB) |  | HTML iconHTML  

    Missing data in very high spatial resolution (VHR) optical imagery take origin mainly from the acquisition conditions. Their accurate reconstruction represents a great methodological challenge because of the complexity and the ill-posed nature of the problem. In this letter, we present three different solutions, with all based on the inpainting approach, which consists in reconstructing the missing regions in a given image by propagating the spectrogeometrical information retrieved from the remaining parts of the image. They rely on the idea to enrich the patch search process by including local image properties or by isometric transformations or to reformulate it under a multiresolution processing scheme, respectively. Thorough experiments conducted on two different VHR images are reported and discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ghost Persistent Scatterers Related to Multiple Signal Reflections

    Page(s): 919 - 923
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB) |  | HTML iconHTML  

    Persistent scatterer interferometry using stacks of very high resolution synthetic aperture radar (SAR) data reveals that single or even patterns of scatterers representing building structures may wrongly be localized below the ground level. In this letter, a case study on a test building model is presented using 3-D SAR simulation methods in order to explain the underlying localization problem. The case study indicates that Ghost-PSs are likely to be related to reflection levels that are higher than three. Moreover, the temporal stability of the amplitude of fivefold bounce signals is confirmed for a SAR data stack. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Real-Time Endmember Extraction on Multicore Processors

    Page(s): 924 - 928
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB) |  | HTML iconHTML  

    In this letter, we discuss the use of multicore processors in the acceleration of endmember extraction algorithms for hyperspectral image unmixing. Specifically, we develop computationally efficient versions of two popular fully automatic endmember extraction algorithms: orthogonal subspace projection and N-FINDR. Our experimental results, based on the analysis of hyperspectral data collected by the National Aeronautics and Space Administration Jet Propulsion Laboratory's Airborne Visible InfraRed Imaging Spectrometer, indicate that endmember extraction algorithms can significantly benefit from these inexpensive high-performance computing platforms, which can offer real-time response with some programming effort. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An Efficient Approach With Scaling Factors for TOPS-Mode SAR Data Focusing

    Page(s): 929 - 933
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    The Terrain Observation by Progressive Scans (TOPS) mode is a novel spaceborne imaging mode which can be used to obtain wide-swath coverage and overcome major drawbacks in conventional ScanSAR. An efficient full-aperture imaging approach, which takes advantage of the two-step focusing technique and the azimuth baseband scaling operation, is presented for processing the TOPS-mode synthetic aperture radar (SAR) data. First, the proposed two-step focusing technique for spotlight and sliding spotlight SAR data focusing is adopted to resolve the aliased Doppler spectrum. Afterward, the following extended chirp scaling processing procedure with azimuth scaling factors is used to implement the residual TOPS raw-data focusing. Since the use of subapertures is avoided and only a limited azimuth-data extension is required, this algorithm is highly efficient. Simulation results validate the proposed imaging approach. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GPR Imaging With RM Algorithm in Layered Mediums

    Page(s): 934 - 938
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (378 KB) |  | HTML iconHTML  

    In ground-penetrating radar (GPR) imaging, the classic range migration (RM) algorithm can work well only when the imaging scene can be modeled as a single homogeneous medium. However, in most GPR field applications, the GPR system and objects operate in different mediums. The space between the antennas and the ground cannot be ignored electromagnetically. In this kind of circumstance, the imaging result of the classic RM algorithm will be blurred or possibly not focused at all, and the object's physical location cannot be interpreted from the imaging result. A layered RM imaging algorithm is proposed in this letter. With the exploding source model, the received field is first back propagated to the ground surface, and then, the classic RM method is carried out to give the final imaging result. Experimental results show that the proposed algorithm can prevent the defocusing of the object and obtain the object's true position. The computational time of the layered RM algorithm does not increase remarkably compared with that of the classic RM algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Autofocus Correction of Phase Distortion Effects on SHARAD Echoes

    Page(s): 939 - 942
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (277 KB) |  | HTML iconHTML  

    SHARAD is a frequency-modulated (15-25 MHz) radar sounder that probes the upper few kilometers of the Martian crust and polar layered deposits. At solar zenith angles less than about 100°, the ionosphere of Mars can induce phase distortion in surface and subsurface radar echoes that substantially degrades the signal-to-noise ratio and vertical resolution of the range-compressed data. We present a range-compression autofocus approach that estimates the phase distortion of SHARAD data along ground-track segments of about 100 km, using a power-law image-sharpness metric and an empirically derived scaling between the phase correction and radar frequency. This method is rapid, yields a greatly improved subsurface image, and provides a means to track regional and temporal changes in the Martian ionosphere. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • TanDEM-X First DEM Acquisition: A Crossing Orbit Experiment

    Page(s): 943 - 947
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB) |  | HTML iconHTML  

    This letter describes the first interferometric acquisitions and results obtained by the TerraSAR-X add-on for Digital Elevation Measurements mission. Due to the large along-track separation between the two satellites during the approaching maneuver and the Earth's rotation, useful interferometric acquisitions were only possible at high latitudes. This resulted in a crossing angle between the ground tracks whose impact was corrected by acquiring the two synthetic-aperture radar images with an opposite squint. The still very large 2-km cross-track baseline resulted in a 3.8-m interferometric height of ambiguity, producing extremely detailed images of the topography of the target area. Results acquired over the October Revolution Island, Russia, are shown and discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Geoscience and Remote Sensing Letters (GRSL) is a monthly publication for short papers (maximum length 5 pages) addressing new ideas and formative concepts in remote sensing as well as important new and timely results and concepts.

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Alejandro C. Frery
Universidade Federal de Alagoas